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Evaluation of 3 Fixation Devices for Tibial-Sided Anterior Cruciate Ligament Graft Backup Fixation
Restoration of stability with return to activity is generally expected after anterior cruciate ligament (ACL) reconstruction; long-term success rates range from 75% to 95%.1 However, graft failure occurs most frequently with soft-tissue grafts fixated only with interference screws.2,3 Fixation failure also occurs more frequently at the tibial site.2 This failure has been attributed to extensive graft slippage in cases of soft-tissue fixation with interference screws.2 Interference screw fixation alone, with a double-looped hamstring tendon graft, fails at 350 N in young human tibiae.4,5 However, failure is limited with use of a bone–tendon–bone graft or with backup fixation, particularly at the tibial site.3 The superiority of bicortical fixation has also been proven.5-7
In addition, as shown in a goat model, ACL graft fixation is a major cause of failure in the immediate postoperative period, before biological incorporation of the graft.8 Fixation techniques for soft-tissue grafts must withstand stresses during the healing period (grafts may take up to 12 weeks to incorporate).9 Failures may result from forces exerted on the graft—forces that may be as high as 450 to 700 N during daily activities.10,11 Within the tibial tunnel, various fixation devices are used, including interference screws, staples, pins, buttons, and interference screw/sheath constructs.12,13 Primary fixation is commonly achieved with interference screws because of their ease of insertion and greater stiffness. However, fixation of the soft-tissue graft is influenced by several variables, including bone density, insertion torque, thread geometry, and interference screw material.14-16 Many of these variables, which are a source of inconsistency and concern during the immediate postoperative period, have led surgeons to seek alternative methods of backup fixation at the tibial site. Nevertheless, good clinical and subjective results have been found after ACL reconstruction with a 4-stranded semitendinosus tendon at 10-year follow-up.17
An anchor used in rotator cuff repair is the SwiveLock system (Arthrex). Major advantages of this system include ease and speed of insertion, good strength, and reduced need for later hardware removal.
We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for ACL reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw. We hypothesized that a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanical strength no different from that provided by backup fixation with a bicortical post at the tibial site. We further hypothesized that SwiveLock backup fixation would provide more strength than fixation with bio-interference screw alone.
Materials and Methods
The design of this study was adapted from one used by Walsh and colleagues,3 who compared 3 fixation methods: retrograde interference screw, suture button, and combined fixation. Tibiae inspected before selection showed no signs of injury or abnormality. Bovine extensor tendons, which lacked any defects along their entire length, were stored in saline 0.9% solution. Both the tibiae and the extensor tendons were stored at –20°C before completion of the tibial-sided ACL reconstruction. Thirty fresh-frozen, skeletally mature porcine proximal tibiae were selected and thawed at 4°C before preparation. Specimens were prepared by potting the diaphysis in fiberglass resin, and a tunnel 9 mm in diameter was drilled through the anteromedial aspect of the tibia.
For consistency, one author (CAV) prepared all 30 specimens. Both tails of all 30 bovine extensor tendons were whip-stitched with No. 2 FiberLoop (Arthrex) 9 mm in diameter. Grafts and tibiae were randomly divided into 3 sample groups. The first group was prepared by antegrade graft fixation within the tibial tunnel using a fully threaded 9×28-mm BioComposite interference screw (Arthrex). The second and third groups used the same primary fixation within the tibial tunnel along with 2 types of secondary fixation. These backup fixation groups included a 4.5-mm titanium bicortical post (Arthrex) and a 4.75-mm BioComposite SwiveLock C anchor (Arthrex) (Figure 1). The FiberLoop at the ends of the distal graft tails for backup groups were fixated 1 cm distal to the tibial tunnel and tapped before insertion of backup devices (Figures 2A, 2B). Insertion was completed after 4.5-mm bicortical and 4.75-mm unicortical drilling and tapping of the anteromedial cortices for the titanium posts and SwiveLocks, respectively. The free ends of the whip-stitched No. 2 FiberLoop were tied to the proximal end of the titanium post with a single surgical knot followed by 5 square knots.3 The free ends of the No. 2 FiberLoop were inserted into the eyelet of the 4.75-mm SwiveLock and 1 cm directly inferior to the tibial tunnel. Interference fit of FiberLoop with SwiveLock was achieved within the corticocancellous bone of the tibiae. All samples retained a 30-mm tendon loop superior to the tibial plateau to simulate intra-articular ACL length. Specimens were then stored at –20°C and thawed at 4°C before biomechanical testing.
Each of the 30 tibiae was tested once. Each testing group consisted of 10 porcine tibiae. The tendons were kept moist during the entire testing procedure by spraying them thoroughly with saline 0.9% solution. Mechanical testing was performed with an Instron 8871 system with a 5-kN load cell secured to the crosshead. A fixed-angle aperture, attached to the testing surface, was adjusted so that the tendon would be pulled in line with the tibial tunnel. A hook fixture suspended from clevis and dowel was used to secure the tendon to the crosshead (Figure 3). A small preload of 5 N manually applied to each sample was followed by a precycling regimen of 10 cycles between 10 N and 50 N at 1 Hz. Precycling was performed to remove slack from the system. Mechanical testing consisted of 500 cycles between 50 N and 250 N at 1 Hz followed by pull to failure at 20 mm per minute. Load and displacement data were recorded at 500 Hz.
An a priori power analysis was not performed because 6 specimens per group in the study from which the testing protocol was adapted demonstrated sufficient power among 3 testing categories.3 In addition, other studies have demonstrated similar testing protocols using 10 specimens per testing group.7,12,13,18 The data for each sample were analyzed with OriginPro 8.0 software (OriginLab). Ultimate load, yield load, stiffness, and cyclic displacement of the 3 sample groups were compared with 1-way analysis of variance (α = 0.05). Holm-Sidak tests were used for post hoc analysis.19P < .05 was statistically significant.
Results
None of the 30 specimens failed during preloading. Modes of failure were consistent among groups. All 10 specimens in the interference-screw-only group failed by graft slippage past the screw in the tibial tunnel. Nineteen of the 20 specimens in the backup-fixation groups failed by graft slippage past the screw and suture cutout through the distal graft tail. In the bicortical-post backup group, 1 failure was attributed to tendon tearing proximal to whip-stitching. There were no instances of hardware breakage or failure of either titanium screw or SwiveLock anchor.
Mean (SD) cyclic displacement was higher in the interference-screw-only group, 3.5 (2.2) mm, than in the SwiveLock backup group, 2.6 (0.5) mm, and the bicortical-post backup group, 2.1 (0.6) mm; no statistical significance was demonstrated between any 2 of these groups alone (P = .12) (Figure 4). Mean (SD) pullout stiffness was higher in the bicortical-post backup group, 192 (48) N/mm, than in the SwiveLock backup group, 164 (53) N/mm, and the screw-only group, 163 (64) N/mm (P = .42) (Figure 5). Mean (SD) initial load at 5 mm of displacement was higher in the bicortical-post backup group, 482 (156) N, and the SwiveLock backup group, 423 (94) N, than in the screw-only group, 381 (169) N (P = .30).
Mean (SD) yield load was higher in the bicortical-post backup group, 829 (253) N, than in the SwiveLock backup group, 642 (172) N, and the interference-screw-only group, 496 (133) N (P = .003). Statistical significance was demonstrated between the screw-only and bicortical-post groups (P = .002) and between the screw-only and SwiveLock groups (P = .048). There was no statistical difference between the bicortical-post and SwiveLock groups (P = .07).
Mean (SD) ultimate load to failure was higher in the bicortical-post backup group, 1148 (186) N, than in the SwiveLock backup group, 1007 (176) N, and the interference-screw-only group, 778 (139) N (Figure 6). The difference was statistically significant, whereby the screw-only group failed at a lower load compared with the bicortical-post group (P < .001) and the SwiveLock group (P = .005). The 2 backup groups were not statistically different (P = .1).
Discussion
We investigated whether a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanically equivalent pullout strength within the tibial tunnel during ACL reconstruction with soft-tissue allografts in comparison either with a fully threaded bio-interference screw backed with a bicortical post or with a fully threaded bio-interference screw without backup fixation. The results of the study support this hypothesis. With SwiveLock used for backup fixation, there was no significant difference in stiffness or cyclic load displacement between the screw-only, SwiveLock, and bicortical-post groups. However, adding backup fixation could particularly help improve fixation consistency. Specifically, although after only 500 cycles there was no statistically significant difference in cyclic displacement, continued cycling may be clinically relevant if graft slippage exceeded limits to allow for healing within the tibial tunnel. Conversely, a significantly larger difference was found between the SwiveLock, bicortical-post, and screw-only groups in yield load and ultimate load to failure. However, there was no significant difference between the SwiveLock and bicortical-post groups.
In this study, interference screw with SwiveLock backup demonstrated a mean (SD) ultimate load to failure of 1007 (176) N, comparable to that found by Walsh and colleagues3 for retrograde bio-interference screw with suture button, 1027 (157.11) N. In a study comparing quadrupled hamstring tibial graft fixation, Intrafix (DePuy Mitek) and an 8×25-mm Bioscrew (Linvatec) demonstrated mean (SD) single-cycle yield loads of 1332 (304) N and 612 (176) N, respectively.13 These results are similar to the ultimate yield loads in the present study: bicortical-post group, 1148 (186) N; SwiveLock group, 1007 (176) N; screw-only group, 778 (139) N. Differences may be attributed to hamstring tendons used in a quadrupled manner in the aforementioned study.12,13 Last, mean (SD) ultimate load to failure in a study that used only a retrograde bio-interference screw (9×20 mm) was 679.00 (109.44) N,3 similar to the 778 (139) N found for interference-screw-only in the present study. The difference is likely attributable to the longer screw (9×28 mm) in our study. Using SwiveLock C in cortical bone, Barber and colleagues18 found mean (SD) loads to failure up to 711.9 (89.1) N.
Clinically, it has been shown that a statistically significant increase in anterior laxity occurred between 4 months and 2 years in 10.7% of patients who underwent hamstring ACL reconstruction.20 The knees were clinically categorized as unstable or severely abnormal. The authors concluded that the clinical outcome was more likely influenced by the methods used to fix the free ends of the graft, specifically with 2 staples or a washer. To simulate early postoperative rehabilitation in the present study, cyclic loading of the graft was performed. Ultimate load to failure was then determined in order to evaluate catastrophic failure strength of the backup fixation devices in comparison with the interference-screw-only group without supplementary fixation.
It has been shown in autologous hamstring ACL reconstruction that a centrally placed polyethylene screw with sheath (Intrafix) performed as well as a standard, eccentrically placed metal interference screw with staple.10 It is therefore logical that backup fixation with use of a similar device (eg, SwiveLock, bicortical post) is necessary to ensure comparable clinical outcomes in relation to a screw/sheath device that has been shown to endure the highest yield loads.2,9,12,13,21-23 Potential benefits of using SwiveLock anchors for backup fixation include a statistically significant increased mean (SD) ultimate yield load of 229 (176) N over interference screw only. These results are similar to those in comparable studies: 218.3 (59.7) N24 and 165 (24.15) N25 in healthy bone with a reported bone mineral density (BMD) of 1.39 g/cm2, similar to that of skeletally mature porcine tibia (1.220-1.675 g/cm²).3 In addition, ease of insertion of this device over a bicortical post was demonstrated. The titanium post required bicortical drilling as well as measurement with a depth gauge to ensure adequate screw length. This process appeared to require more time during specimen preparation and theoretically could prove to be more dangerous clinically.7 However, caution in using a SwiveLock anchor in osteoporotic bone is advised because of reduced pullout strength.26 In this case, bicortical-post backup fixation may be more suitable. Moreover, although not demonstrated in this study, hardware prominence and irritation with a post may cause postoperative morbidity necessitating future removal.20 Hardware removal was the most common reason for additional surgery using hamstring tendons as graft.20 A second surgery for hardware removal was required in 21% of these patients.20 This is unlikely to occur with a SwiveLock, as the anchor is buried within cortical bone.
Limitations
Regarding use of nonhuman tissues in a biomechanical model, porcine tibiae and bovine extensor tendons were used because of availability, consistency among specimens, and cost-effectiveness. However, bovine extensor tendons have been shown to exhibit stiffness and viscoelastic properties similar to those of a human hamstring graft.27 In addition, the BMD of the porcine tibiae used in this study was not tested because of time involved and cost-efficiency. However, it has been shown that average BMD of porcine tibiae, 1.220-1.675 g/cm², is similar to that in a young athletic population, 1.24-1.62 g/cm2.3,28-31 We therefore assumed similarity to a young athletic population and uniformity of BMD of the porcine tibiae used in this study.
In addition, the biomechanical testing protocol did not simulate physiologic loading within the tibial tunnel. Moreover, the testing protocol used loads of only 250 N during cyclic testing for 500 cycles. This simulates only the early rehabilitation period and not the healing period, which may last up to 12 weeks.9 In addition, as previously mentioned, forces on the graft may be as high as 450 to 700 N.11,32 Pullout testing in line with the long axis of the tibia was performed in order to compare mechanical testing results with those of similar studies.3,12,13 Last, the P of .07 for the comparison of ultimate load to failure between the 2 backup fixation groups suggests that this study may have been underpowered.
Conclusion
This study demonstrated an effective, alternative, and equivalent backup fixation device that can help prevent graft slippage within the tibial tunnel during soft-tissue ACL reconstruction. Potential benefits of using SwiveLock anchors for backup fixation include a significantly increased ultimate yield load (229 N) when supplementing an interference screw, ease of insertion compared with a bicortical post, and the improbable need for future hardware removal. We support using SwiveLock for supplementary fixation at the tibial tunnel site when using soft-tissue grafts in ACL reconstruction.
1. Wetzler MJ, Bartolozzi AR, Gillespie MJ, Rubenstein DL, Ciccotti MG, Miller LS. Revision anterior cruciate ligament reconstruction. Oper Tech Orthop. 1996;6(3):181-189.
2. Scheffler SU, Südkamp NP, Göckenjan A, Hoffmann RF, Weiler A. Biomechanical comparison of hamstring and patellar tendon graft anterior cruciate ligament reconstruction techniques: the impact of fixation level and fixation method under cyclic loading. Arthroscopy. 2002;18(3):304-315.
3. Walsh MP, Wijdicks CA, Parker JB, Hapa O, LaPrade RF. A comparison between a retrograde interference screw, suture button, and combined fixation on the tibial side in an all-inside anterior cruciate ligament reconstruction: a biomechanical study in a porcine model. Am J Sports Med. 2009;37(1):160-167.
4. Howell SM, Hull ML. Aggressive rehabilitation using hamstring tendons: graft construct, tibial tunnel placement, fixation properties, and clinical outcome. Am J Knee Surg. 1998;11(2):120-127.
5. Magen HE, Howell SM, Hull ML. Structural properties of six tibial fixation methods for anterior cruciate ligament soft tissue grafts. Am J Sports Med. 1999;27(1):35-43.
6. Beynnon BD, Meriam CM, Ryder SH, Fleming BC, Johnson RJ. The effect of screw insertion torque on tendons fixed with spiked washers. Am J Sports Med. 1998;26(4):536-539.
7. Post WR, King SS. Neurovascular risk of bicortical tibial drilling for screw and spiked washer fixation of soft-tissue anterior cruciate ligament graft. Arthroscopy. 2001;17(3):244-247.
8. Holden JP, Grood ES, Butler DL, et al. Biomechanics of fascia lata ligament replacements: early postoperative changes in the goat. J Orthop Res. 1988;6(5):639-647.
9. Rodeo SA, Arnoczky SP, Torzilli PA, Hidaka C, Warren RF. Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am. 1993;75(12):1795-1803.
10. Frank CB, Jackson DW. The science of reconstruction of the anterior cruciate ligament. J Bone Joint Surg Am. 1997;79(10):1556-1576.
11. Markolf KL, Willems MJ, Jackson SR, Finerman GA. In situ calibration of miniature sensors implanted into the anterior cruciate ligament. Part I: strain measurements. J Orthop Res. 1998;16(4):455-463.
12. Kousa P, Teppo LN, Jarvinen TL, Vihavainen M, Kannus P, Jarvinen M. The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction: I. Femoral site. Am J Sports Med. 2003;3 (2)1:174-181.
13. Kousa P, Jarvinen TL, Vihavainen M, Kannus P, Jarvinen M. The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction: II. Tibial site. Am J Sports Med. 2003;31(2):182-188.
14. Brand JC Jr, Pienkowski D, Steenlage E, Hamilton D, Johnson DL, Caborn DN. Interference screw fixation strength of a quadrupled hamstring tendon graft is directly related to bone mineral density and insertion torque. Am J Sports Med. 2000;28(5):705-710.
15. Weiler A, Hoffmann RF, Siepe CJ, Kolbeck SF, Südkamp NP. The influence of screw geometry on hamstring tendon interference fit fixation. Am J Sports Med. 2000;28(3):356-359.
16. Weiler A, Hoffmann RF, Stähelin AC, Bail HJ, Siepe CJ, Südkamp NP. Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone. Arthroscopy. 1998;14(1):29-37.
17. Streich NA, Reichenbacher S, Barié A, Buchner M, Schmitt H. Long-term outcome of anterior cruciate ligament reconstruction with an autologous four-strand semitendinosus tendon autograft. Int Orthop. 2013;37(2):279-284.
18. Barber FA, Herbert MA, Beavis C, Barrera Oro F. Suture anchor materials, eyelets, and designs: update 2008. Arthroscopy. 2008;24(8):859-867.
19. Aickin M, Gensler H. Adjusting for multiple testing when reporting research results: the Bonferroni vs Holm methods. Am J Public Health. 1996;86(5):726-728.
20. Howell SM, Deutsch ML. Comparison of endoscopic and two-incision techniques for reconstructing a torn anterior cruciate ligament using hamstring tendons. Arthroscopy. 1999;15(6):594-606.
21. Gwynne-Jones DP, Draffin J, Vane A, Craig R, McMahon S. Failure strengths of concentric and eccentric implants for hamstring graft fixation. ANZ J Surg. 2008;78(3):177-181.
22. Hayes DA, Watts MC, Tevelen GA, Crawford RW. Central versus peripheral tibial screw placement in hamstring anterior cruciate ligament reconstruction: in vitro biomechanics. Arthroscopy. 2005;21(6):703-706.
23. Shino K, Pflaster DS. Comparison of eccentric and concentric screw placement for hamstring graft fixation in the tibial tunnel. Knee Surg Sports Traumatol Arthrosc. 2000;8(2):73-75.
24. Prevrhal S, Fuerst T, Fan B, et al. Quantitative ultrasound of the tibia depends on both cortical density and thickness. Osteoporosis Int. 2001;12(1):28-34.
25. Pietschmann MF, Gülecyüz MF, Fieseler S, et al. Biomechanical stability of knotless suture anchors used in rotator cuff repair in healthy and osteopenic bone. Arthroscopy. 2010;26(8):1035-1044.
26. Burns JP, Snyder SJ, Albritton M. Arthroscopic rotator cuff repair using triple-loaded anchors, suture shuttles, and suture savers. J Am Acad Orthop Surg. 2007;15(7):432-444.
27. Tetsumura S, Fujita A, Nakajima M, Abe M. Biomechanical comparison of different fixation methods on the tibial side in anterior cruciate ligament reconstruction: a biomechanical study in porcine tibial bone. J Orthop Sci. 2006;11(3):278-282.
28. Alfredson H, Nordstrom P, Lorentzon R. Total and regional bone mass in female soccer players. Calcif Tissue Int. 1996;59(6):438-442.
29. Nevill AM, Holder RL, Stewart AD. Modeling elite male athletes’ peripheral bone mass, assessed using regional dual x-ray absorptiometry. Bone. 2003;32(1):62-68.
30. Nordström P, Lorentzon R. Site-specific bone mass differences of the lower extremities in 17-year-old ice hockey players. Calcif Tissue Int. 1996;59(6):4443-4448.
31. Patzer T, Santo G, Olender GD, Wellmann M, Hurschler C, Schofer MD. Suprapectoral or subpectoral position for biceps tenodesis: biomechanical comparison of four different techniques in both positions. J Shoulder Elbow Surg. 2012;21(1):116-125.
32. De Wall M, Scholes CJ, Patel S, Coolican MR, Parker DA. Tibial fixation in anterior cruciate ligament reconstruction: a prospective randomized study comparing metal interference screw and staples with a centrally placed polyethylene screw and sheath. Am J Sports Med. 2011;39(9):1858-1864.
Restoration of stability with return to activity is generally expected after anterior cruciate ligament (ACL) reconstruction; long-term success rates range from 75% to 95%.1 However, graft failure occurs most frequently with soft-tissue grafts fixated only with interference screws.2,3 Fixation failure also occurs more frequently at the tibial site.2 This failure has been attributed to extensive graft slippage in cases of soft-tissue fixation with interference screws.2 Interference screw fixation alone, with a double-looped hamstring tendon graft, fails at 350 N in young human tibiae.4,5 However, failure is limited with use of a bone–tendon–bone graft or with backup fixation, particularly at the tibial site.3 The superiority of bicortical fixation has also been proven.5-7
In addition, as shown in a goat model, ACL graft fixation is a major cause of failure in the immediate postoperative period, before biological incorporation of the graft.8 Fixation techniques for soft-tissue grafts must withstand stresses during the healing period (grafts may take up to 12 weeks to incorporate).9 Failures may result from forces exerted on the graft—forces that may be as high as 450 to 700 N during daily activities.10,11 Within the tibial tunnel, various fixation devices are used, including interference screws, staples, pins, buttons, and interference screw/sheath constructs.12,13 Primary fixation is commonly achieved with interference screws because of their ease of insertion and greater stiffness. However, fixation of the soft-tissue graft is influenced by several variables, including bone density, insertion torque, thread geometry, and interference screw material.14-16 Many of these variables, which are a source of inconsistency and concern during the immediate postoperative period, have led surgeons to seek alternative methods of backup fixation at the tibial site. Nevertheless, good clinical and subjective results have been found after ACL reconstruction with a 4-stranded semitendinosus tendon at 10-year follow-up.17
An anchor used in rotator cuff repair is the SwiveLock system (Arthrex). Major advantages of this system include ease and speed of insertion, good strength, and reduced need for later hardware removal.
We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for ACL reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw. We hypothesized that a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanical strength no different from that provided by backup fixation with a bicortical post at the tibial site. We further hypothesized that SwiveLock backup fixation would provide more strength than fixation with bio-interference screw alone.
Materials and Methods
The design of this study was adapted from one used by Walsh and colleagues,3 who compared 3 fixation methods: retrograde interference screw, suture button, and combined fixation. Tibiae inspected before selection showed no signs of injury or abnormality. Bovine extensor tendons, which lacked any defects along their entire length, were stored in saline 0.9% solution. Both the tibiae and the extensor tendons were stored at –20°C before completion of the tibial-sided ACL reconstruction. Thirty fresh-frozen, skeletally mature porcine proximal tibiae were selected and thawed at 4°C before preparation. Specimens were prepared by potting the diaphysis in fiberglass resin, and a tunnel 9 mm in diameter was drilled through the anteromedial aspect of the tibia.
For consistency, one author (CAV) prepared all 30 specimens. Both tails of all 30 bovine extensor tendons were whip-stitched with No. 2 FiberLoop (Arthrex) 9 mm in diameter. Grafts and tibiae were randomly divided into 3 sample groups. The first group was prepared by antegrade graft fixation within the tibial tunnel using a fully threaded 9×28-mm BioComposite interference screw (Arthrex). The second and third groups used the same primary fixation within the tibial tunnel along with 2 types of secondary fixation. These backup fixation groups included a 4.5-mm titanium bicortical post (Arthrex) and a 4.75-mm BioComposite SwiveLock C anchor (Arthrex) (Figure 1). The FiberLoop at the ends of the distal graft tails for backup groups were fixated 1 cm distal to the tibial tunnel and tapped before insertion of backup devices (Figures 2A, 2B). Insertion was completed after 4.5-mm bicortical and 4.75-mm unicortical drilling and tapping of the anteromedial cortices for the titanium posts and SwiveLocks, respectively. The free ends of the whip-stitched No. 2 FiberLoop were tied to the proximal end of the titanium post with a single surgical knot followed by 5 square knots.3 The free ends of the No. 2 FiberLoop were inserted into the eyelet of the 4.75-mm SwiveLock and 1 cm directly inferior to the tibial tunnel. Interference fit of FiberLoop with SwiveLock was achieved within the corticocancellous bone of the tibiae. All samples retained a 30-mm tendon loop superior to the tibial plateau to simulate intra-articular ACL length. Specimens were then stored at –20°C and thawed at 4°C before biomechanical testing.
Each of the 30 tibiae was tested once. Each testing group consisted of 10 porcine tibiae. The tendons were kept moist during the entire testing procedure by spraying them thoroughly with saline 0.9% solution. Mechanical testing was performed with an Instron 8871 system with a 5-kN load cell secured to the crosshead. A fixed-angle aperture, attached to the testing surface, was adjusted so that the tendon would be pulled in line with the tibial tunnel. A hook fixture suspended from clevis and dowel was used to secure the tendon to the crosshead (Figure 3). A small preload of 5 N manually applied to each sample was followed by a precycling regimen of 10 cycles between 10 N and 50 N at 1 Hz. Precycling was performed to remove slack from the system. Mechanical testing consisted of 500 cycles between 50 N and 250 N at 1 Hz followed by pull to failure at 20 mm per minute. Load and displacement data were recorded at 500 Hz.
An a priori power analysis was not performed because 6 specimens per group in the study from which the testing protocol was adapted demonstrated sufficient power among 3 testing categories.3 In addition, other studies have demonstrated similar testing protocols using 10 specimens per testing group.7,12,13,18 The data for each sample were analyzed with OriginPro 8.0 software (OriginLab). Ultimate load, yield load, stiffness, and cyclic displacement of the 3 sample groups were compared with 1-way analysis of variance (α = 0.05). Holm-Sidak tests were used for post hoc analysis.19P < .05 was statistically significant.
Results
None of the 30 specimens failed during preloading. Modes of failure were consistent among groups. All 10 specimens in the interference-screw-only group failed by graft slippage past the screw in the tibial tunnel. Nineteen of the 20 specimens in the backup-fixation groups failed by graft slippage past the screw and suture cutout through the distal graft tail. In the bicortical-post backup group, 1 failure was attributed to tendon tearing proximal to whip-stitching. There were no instances of hardware breakage or failure of either titanium screw or SwiveLock anchor.
Mean (SD) cyclic displacement was higher in the interference-screw-only group, 3.5 (2.2) mm, than in the SwiveLock backup group, 2.6 (0.5) mm, and the bicortical-post backup group, 2.1 (0.6) mm; no statistical significance was demonstrated between any 2 of these groups alone (P = .12) (Figure 4). Mean (SD) pullout stiffness was higher in the bicortical-post backup group, 192 (48) N/mm, than in the SwiveLock backup group, 164 (53) N/mm, and the screw-only group, 163 (64) N/mm (P = .42) (Figure 5). Mean (SD) initial load at 5 mm of displacement was higher in the bicortical-post backup group, 482 (156) N, and the SwiveLock backup group, 423 (94) N, than in the screw-only group, 381 (169) N (P = .30).
Mean (SD) yield load was higher in the bicortical-post backup group, 829 (253) N, than in the SwiveLock backup group, 642 (172) N, and the interference-screw-only group, 496 (133) N (P = .003). Statistical significance was demonstrated between the screw-only and bicortical-post groups (P = .002) and between the screw-only and SwiveLock groups (P = .048). There was no statistical difference between the bicortical-post and SwiveLock groups (P = .07).
Mean (SD) ultimate load to failure was higher in the bicortical-post backup group, 1148 (186) N, than in the SwiveLock backup group, 1007 (176) N, and the interference-screw-only group, 778 (139) N (Figure 6). The difference was statistically significant, whereby the screw-only group failed at a lower load compared with the bicortical-post group (P < .001) and the SwiveLock group (P = .005). The 2 backup groups were not statistically different (P = .1).
Discussion
We investigated whether a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanically equivalent pullout strength within the tibial tunnel during ACL reconstruction with soft-tissue allografts in comparison either with a fully threaded bio-interference screw backed with a bicortical post or with a fully threaded bio-interference screw without backup fixation. The results of the study support this hypothesis. With SwiveLock used for backup fixation, there was no significant difference in stiffness or cyclic load displacement between the screw-only, SwiveLock, and bicortical-post groups. However, adding backup fixation could particularly help improve fixation consistency. Specifically, although after only 500 cycles there was no statistically significant difference in cyclic displacement, continued cycling may be clinically relevant if graft slippage exceeded limits to allow for healing within the tibial tunnel. Conversely, a significantly larger difference was found between the SwiveLock, bicortical-post, and screw-only groups in yield load and ultimate load to failure. However, there was no significant difference between the SwiveLock and bicortical-post groups.
In this study, interference screw with SwiveLock backup demonstrated a mean (SD) ultimate load to failure of 1007 (176) N, comparable to that found by Walsh and colleagues3 for retrograde bio-interference screw with suture button, 1027 (157.11) N. In a study comparing quadrupled hamstring tibial graft fixation, Intrafix (DePuy Mitek) and an 8×25-mm Bioscrew (Linvatec) demonstrated mean (SD) single-cycle yield loads of 1332 (304) N and 612 (176) N, respectively.13 These results are similar to the ultimate yield loads in the present study: bicortical-post group, 1148 (186) N; SwiveLock group, 1007 (176) N; screw-only group, 778 (139) N. Differences may be attributed to hamstring tendons used in a quadrupled manner in the aforementioned study.12,13 Last, mean (SD) ultimate load to failure in a study that used only a retrograde bio-interference screw (9×20 mm) was 679.00 (109.44) N,3 similar to the 778 (139) N found for interference-screw-only in the present study. The difference is likely attributable to the longer screw (9×28 mm) in our study. Using SwiveLock C in cortical bone, Barber and colleagues18 found mean (SD) loads to failure up to 711.9 (89.1) N.
Clinically, it has been shown that a statistically significant increase in anterior laxity occurred between 4 months and 2 years in 10.7% of patients who underwent hamstring ACL reconstruction.20 The knees were clinically categorized as unstable or severely abnormal. The authors concluded that the clinical outcome was more likely influenced by the methods used to fix the free ends of the graft, specifically with 2 staples or a washer. To simulate early postoperative rehabilitation in the present study, cyclic loading of the graft was performed. Ultimate load to failure was then determined in order to evaluate catastrophic failure strength of the backup fixation devices in comparison with the interference-screw-only group without supplementary fixation.
It has been shown in autologous hamstring ACL reconstruction that a centrally placed polyethylene screw with sheath (Intrafix) performed as well as a standard, eccentrically placed metal interference screw with staple.10 It is therefore logical that backup fixation with use of a similar device (eg, SwiveLock, bicortical post) is necessary to ensure comparable clinical outcomes in relation to a screw/sheath device that has been shown to endure the highest yield loads.2,9,12,13,21-23 Potential benefits of using SwiveLock anchors for backup fixation include a statistically significant increased mean (SD) ultimate yield load of 229 (176) N over interference screw only. These results are similar to those in comparable studies: 218.3 (59.7) N24 and 165 (24.15) N25 in healthy bone with a reported bone mineral density (BMD) of 1.39 g/cm2, similar to that of skeletally mature porcine tibia (1.220-1.675 g/cm²).3 In addition, ease of insertion of this device over a bicortical post was demonstrated. The titanium post required bicortical drilling as well as measurement with a depth gauge to ensure adequate screw length. This process appeared to require more time during specimen preparation and theoretically could prove to be more dangerous clinically.7 However, caution in using a SwiveLock anchor in osteoporotic bone is advised because of reduced pullout strength.26 In this case, bicortical-post backup fixation may be more suitable. Moreover, although not demonstrated in this study, hardware prominence and irritation with a post may cause postoperative morbidity necessitating future removal.20 Hardware removal was the most common reason for additional surgery using hamstring tendons as graft.20 A second surgery for hardware removal was required in 21% of these patients.20 This is unlikely to occur with a SwiveLock, as the anchor is buried within cortical bone.
Limitations
Regarding use of nonhuman tissues in a biomechanical model, porcine tibiae and bovine extensor tendons were used because of availability, consistency among specimens, and cost-effectiveness. However, bovine extensor tendons have been shown to exhibit stiffness and viscoelastic properties similar to those of a human hamstring graft.27 In addition, the BMD of the porcine tibiae used in this study was not tested because of time involved and cost-efficiency. However, it has been shown that average BMD of porcine tibiae, 1.220-1.675 g/cm², is similar to that in a young athletic population, 1.24-1.62 g/cm2.3,28-31 We therefore assumed similarity to a young athletic population and uniformity of BMD of the porcine tibiae used in this study.
In addition, the biomechanical testing protocol did not simulate physiologic loading within the tibial tunnel. Moreover, the testing protocol used loads of only 250 N during cyclic testing for 500 cycles. This simulates only the early rehabilitation period and not the healing period, which may last up to 12 weeks.9 In addition, as previously mentioned, forces on the graft may be as high as 450 to 700 N.11,32 Pullout testing in line with the long axis of the tibia was performed in order to compare mechanical testing results with those of similar studies.3,12,13 Last, the P of .07 for the comparison of ultimate load to failure between the 2 backup fixation groups suggests that this study may have been underpowered.
Conclusion
This study demonstrated an effective, alternative, and equivalent backup fixation device that can help prevent graft slippage within the tibial tunnel during soft-tissue ACL reconstruction. Potential benefits of using SwiveLock anchors for backup fixation include a significantly increased ultimate yield load (229 N) when supplementing an interference screw, ease of insertion compared with a bicortical post, and the improbable need for future hardware removal. We support using SwiveLock for supplementary fixation at the tibial tunnel site when using soft-tissue grafts in ACL reconstruction.
Restoration of stability with return to activity is generally expected after anterior cruciate ligament (ACL) reconstruction; long-term success rates range from 75% to 95%.1 However, graft failure occurs most frequently with soft-tissue grafts fixated only with interference screws.2,3 Fixation failure also occurs more frequently at the tibial site.2 This failure has been attributed to extensive graft slippage in cases of soft-tissue fixation with interference screws.2 Interference screw fixation alone, with a double-looped hamstring tendon graft, fails at 350 N in young human tibiae.4,5 However, failure is limited with use of a bone–tendon–bone graft or with backup fixation, particularly at the tibial site.3 The superiority of bicortical fixation has also been proven.5-7
In addition, as shown in a goat model, ACL graft fixation is a major cause of failure in the immediate postoperative period, before biological incorporation of the graft.8 Fixation techniques for soft-tissue grafts must withstand stresses during the healing period (grafts may take up to 12 weeks to incorporate).9 Failures may result from forces exerted on the graft—forces that may be as high as 450 to 700 N during daily activities.10,11 Within the tibial tunnel, various fixation devices are used, including interference screws, staples, pins, buttons, and interference screw/sheath constructs.12,13 Primary fixation is commonly achieved with interference screws because of their ease of insertion and greater stiffness. However, fixation of the soft-tissue graft is influenced by several variables, including bone density, insertion torque, thread geometry, and interference screw material.14-16 Many of these variables, which are a source of inconsistency and concern during the immediate postoperative period, have led surgeons to seek alternative methods of backup fixation at the tibial site. Nevertheless, good clinical and subjective results have been found after ACL reconstruction with a 4-stranded semitendinosus tendon at 10-year follow-up.17
An anchor used in rotator cuff repair is the SwiveLock system (Arthrex). Major advantages of this system include ease and speed of insertion, good strength, and reduced need for later hardware removal.
We conducted a study to biomechanically evaluate 3 methods of tibial-sided fixation for ACL reconstruction: fully threaded interference screw only, interference screw backed with 4.75-mm SwiveLock anchor, and fully threaded bio-interference screw backed with 4.5-mm bicortical screw. We hypothesized that a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanical strength no different from that provided by backup fixation with a bicortical post at the tibial site. We further hypothesized that SwiveLock backup fixation would provide more strength than fixation with bio-interference screw alone.
Materials and Methods
The design of this study was adapted from one used by Walsh and colleagues,3 who compared 3 fixation methods: retrograde interference screw, suture button, and combined fixation. Tibiae inspected before selection showed no signs of injury or abnormality. Bovine extensor tendons, which lacked any defects along their entire length, were stored in saline 0.9% solution. Both the tibiae and the extensor tendons were stored at –20°C before completion of the tibial-sided ACL reconstruction. Thirty fresh-frozen, skeletally mature porcine proximal tibiae were selected and thawed at 4°C before preparation. Specimens were prepared by potting the diaphysis in fiberglass resin, and a tunnel 9 mm in diameter was drilled through the anteromedial aspect of the tibia.
For consistency, one author (CAV) prepared all 30 specimens. Both tails of all 30 bovine extensor tendons were whip-stitched with No. 2 FiberLoop (Arthrex) 9 mm in diameter. Grafts and tibiae were randomly divided into 3 sample groups. The first group was prepared by antegrade graft fixation within the tibial tunnel using a fully threaded 9×28-mm BioComposite interference screw (Arthrex). The second and third groups used the same primary fixation within the tibial tunnel along with 2 types of secondary fixation. These backup fixation groups included a 4.5-mm titanium bicortical post (Arthrex) and a 4.75-mm BioComposite SwiveLock C anchor (Arthrex) (Figure 1). The FiberLoop at the ends of the distal graft tails for backup groups were fixated 1 cm distal to the tibial tunnel and tapped before insertion of backup devices (Figures 2A, 2B). Insertion was completed after 4.5-mm bicortical and 4.75-mm unicortical drilling and tapping of the anteromedial cortices for the titanium posts and SwiveLocks, respectively. The free ends of the whip-stitched No. 2 FiberLoop were tied to the proximal end of the titanium post with a single surgical knot followed by 5 square knots.3 The free ends of the No. 2 FiberLoop were inserted into the eyelet of the 4.75-mm SwiveLock and 1 cm directly inferior to the tibial tunnel. Interference fit of FiberLoop with SwiveLock was achieved within the corticocancellous bone of the tibiae. All samples retained a 30-mm tendon loop superior to the tibial plateau to simulate intra-articular ACL length. Specimens were then stored at –20°C and thawed at 4°C before biomechanical testing.
Each of the 30 tibiae was tested once. Each testing group consisted of 10 porcine tibiae. The tendons were kept moist during the entire testing procedure by spraying them thoroughly with saline 0.9% solution. Mechanical testing was performed with an Instron 8871 system with a 5-kN load cell secured to the crosshead. A fixed-angle aperture, attached to the testing surface, was adjusted so that the tendon would be pulled in line with the tibial tunnel. A hook fixture suspended from clevis and dowel was used to secure the tendon to the crosshead (Figure 3). A small preload of 5 N manually applied to each sample was followed by a precycling regimen of 10 cycles between 10 N and 50 N at 1 Hz. Precycling was performed to remove slack from the system. Mechanical testing consisted of 500 cycles between 50 N and 250 N at 1 Hz followed by pull to failure at 20 mm per minute. Load and displacement data were recorded at 500 Hz.
An a priori power analysis was not performed because 6 specimens per group in the study from which the testing protocol was adapted demonstrated sufficient power among 3 testing categories.3 In addition, other studies have demonstrated similar testing protocols using 10 specimens per testing group.7,12,13,18 The data for each sample were analyzed with OriginPro 8.0 software (OriginLab). Ultimate load, yield load, stiffness, and cyclic displacement of the 3 sample groups were compared with 1-way analysis of variance (α = 0.05). Holm-Sidak tests were used for post hoc analysis.19P < .05 was statistically significant.
Results
None of the 30 specimens failed during preloading. Modes of failure were consistent among groups. All 10 specimens in the interference-screw-only group failed by graft slippage past the screw in the tibial tunnel. Nineteen of the 20 specimens in the backup-fixation groups failed by graft slippage past the screw and suture cutout through the distal graft tail. In the bicortical-post backup group, 1 failure was attributed to tendon tearing proximal to whip-stitching. There were no instances of hardware breakage or failure of either titanium screw or SwiveLock anchor.
Mean (SD) cyclic displacement was higher in the interference-screw-only group, 3.5 (2.2) mm, than in the SwiveLock backup group, 2.6 (0.5) mm, and the bicortical-post backup group, 2.1 (0.6) mm; no statistical significance was demonstrated between any 2 of these groups alone (P = .12) (Figure 4). Mean (SD) pullout stiffness was higher in the bicortical-post backup group, 192 (48) N/mm, than in the SwiveLock backup group, 164 (53) N/mm, and the screw-only group, 163 (64) N/mm (P = .42) (Figure 5). Mean (SD) initial load at 5 mm of displacement was higher in the bicortical-post backup group, 482 (156) N, and the SwiveLock backup group, 423 (94) N, than in the screw-only group, 381 (169) N (P = .30).
Mean (SD) yield load was higher in the bicortical-post backup group, 829 (253) N, than in the SwiveLock backup group, 642 (172) N, and the interference-screw-only group, 496 (133) N (P = .003). Statistical significance was demonstrated between the screw-only and bicortical-post groups (P = .002) and between the screw-only and SwiveLock groups (P = .048). There was no statistical difference between the bicortical-post and SwiveLock groups (P = .07).
Mean (SD) ultimate load to failure was higher in the bicortical-post backup group, 1148 (186) N, than in the SwiveLock backup group, 1007 (176) N, and the interference-screw-only group, 778 (139) N (Figure 6). The difference was statistically significant, whereby the screw-only group failed at a lower load compared with the bicortical-post group (P < .001) and the SwiveLock group (P = .005). The 2 backup groups were not statistically different (P = .1).
Discussion
We investigated whether a fully threaded bio-interference screw backed with a 4.75-mm SwiveLock anchor would provide mechanically equivalent pullout strength within the tibial tunnel during ACL reconstruction with soft-tissue allografts in comparison either with a fully threaded bio-interference screw backed with a bicortical post or with a fully threaded bio-interference screw without backup fixation. The results of the study support this hypothesis. With SwiveLock used for backup fixation, there was no significant difference in stiffness or cyclic load displacement between the screw-only, SwiveLock, and bicortical-post groups. However, adding backup fixation could particularly help improve fixation consistency. Specifically, although after only 500 cycles there was no statistically significant difference in cyclic displacement, continued cycling may be clinically relevant if graft slippage exceeded limits to allow for healing within the tibial tunnel. Conversely, a significantly larger difference was found between the SwiveLock, bicortical-post, and screw-only groups in yield load and ultimate load to failure. However, there was no significant difference between the SwiveLock and bicortical-post groups.
In this study, interference screw with SwiveLock backup demonstrated a mean (SD) ultimate load to failure of 1007 (176) N, comparable to that found by Walsh and colleagues3 for retrograde bio-interference screw with suture button, 1027 (157.11) N. In a study comparing quadrupled hamstring tibial graft fixation, Intrafix (DePuy Mitek) and an 8×25-mm Bioscrew (Linvatec) demonstrated mean (SD) single-cycle yield loads of 1332 (304) N and 612 (176) N, respectively.13 These results are similar to the ultimate yield loads in the present study: bicortical-post group, 1148 (186) N; SwiveLock group, 1007 (176) N; screw-only group, 778 (139) N. Differences may be attributed to hamstring tendons used in a quadrupled manner in the aforementioned study.12,13 Last, mean (SD) ultimate load to failure in a study that used only a retrograde bio-interference screw (9×20 mm) was 679.00 (109.44) N,3 similar to the 778 (139) N found for interference-screw-only in the present study. The difference is likely attributable to the longer screw (9×28 mm) in our study. Using SwiveLock C in cortical bone, Barber and colleagues18 found mean (SD) loads to failure up to 711.9 (89.1) N.
Clinically, it has been shown that a statistically significant increase in anterior laxity occurred between 4 months and 2 years in 10.7% of patients who underwent hamstring ACL reconstruction.20 The knees were clinically categorized as unstable or severely abnormal. The authors concluded that the clinical outcome was more likely influenced by the methods used to fix the free ends of the graft, specifically with 2 staples or a washer. To simulate early postoperative rehabilitation in the present study, cyclic loading of the graft was performed. Ultimate load to failure was then determined in order to evaluate catastrophic failure strength of the backup fixation devices in comparison with the interference-screw-only group without supplementary fixation.
It has been shown in autologous hamstring ACL reconstruction that a centrally placed polyethylene screw with sheath (Intrafix) performed as well as a standard, eccentrically placed metal interference screw with staple.10 It is therefore logical that backup fixation with use of a similar device (eg, SwiveLock, bicortical post) is necessary to ensure comparable clinical outcomes in relation to a screw/sheath device that has been shown to endure the highest yield loads.2,9,12,13,21-23 Potential benefits of using SwiveLock anchors for backup fixation include a statistically significant increased mean (SD) ultimate yield load of 229 (176) N over interference screw only. These results are similar to those in comparable studies: 218.3 (59.7) N24 and 165 (24.15) N25 in healthy bone with a reported bone mineral density (BMD) of 1.39 g/cm2, similar to that of skeletally mature porcine tibia (1.220-1.675 g/cm²).3 In addition, ease of insertion of this device over a bicortical post was demonstrated. The titanium post required bicortical drilling as well as measurement with a depth gauge to ensure adequate screw length. This process appeared to require more time during specimen preparation and theoretically could prove to be more dangerous clinically.7 However, caution in using a SwiveLock anchor in osteoporotic bone is advised because of reduced pullout strength.26 In this case, bicortical-post backup fixation may be more suitable. Moreover, although not demonstrated in this study, hardware prominence and irritation with a post may cause postoperative morbidity necessitating future removal.20 Hardware removal was the most common reason for additional surgery using hamstring tendons as graft.20 A second surgery for hardware removal was required in 21% of these patients.20 This is unlikely to occur with a SwiveLock, as the anchor is buried within cortical bone.
Limitations
Regarding use of nonhuman tissues in a biomechanical model, porcine tibiae and bovine extensor tendons were used because of availability, consistency among specimens, and cost-effectiveness. However, bovine extensor tendons have been shown to exhibit stiffness and viscoelastic properties similar to those of a human hamstring graft.27 In addition, the BMD of the porcine tibiae used in this study was not tested because of time involved and cost-efficiency. However, it has been shown that average BMD of porcine tibiae, 1.220-1.675 g/cm², is similar to that in a young athletic population, 1.24-1.62 g/cm2.3,28-31 We therefore assumed similarity to a young athletic population and uniformity of BMD of the porcine tibiae used in this study.
In addition, the biomechanical testing protocol did not simulate physiologic loading within the tibial tunnel. Moreover, the testing protocol used loads of only 250 N during cyclic testing for 500 cycles. This simulates only the early rehabilitation period and not the healing period, which may last up to 12 weeks.9 In addition, as previously mentioned, forces on the graft may be as high as 450 to 700 N.11,32 Pullout testing in line with the long axis of the tibia was performed in order to compare mechanical testing results with those of similar studies.3,12,13 Last, the P of .07 for the comparison of ultimate load to failure between the 2 backup fixation groups suggests that this study may have been underpowered.
Conclusion
This study demonstrated an effective, alternative, and equivalent backup fixation device that can help prevent graft slippage within the tibial tunnel during soft-tissue ACL reconstruction. Potential benefits of using SwiveLock anchors for backup fixation include a significantly increased ultimate yield load (229 N) when supplementing an interference screw, ease of insertion compared with a bicortical post, and the improbable need for future hardware removal. We support using SwiveLock for supplementary fixation at the tibial tunnel site when using soft-tissue grafts in ACL reconstruction.
1. Wetzler MJ, Bartolozzi AR, Gillespie MJ, Rubenstein DL, Ciccotti MG, Miller LS. Revision anterior cruciate ligament reconstruction. Oper Tech Orthop. 1996;6(3):181-189.
2. Scheffler SU, Südkamp NP, Göckenjan A, Hoffmann RF, Weiler A. Biomechanical comparison of hamstring and patellar tendon graft anterior cruciate ligament reconstruction techniques: the impact of fixation level and fixation method under cyclic loading. Arthroscopy. 2002;18(3):304-315.
3. Walsh MP, Wijdicks CA, Parker JB, Hapa O, LaPrade RF. A comparison between a retrograde interference screw, suture button, and combined fixation on the tibial side in an all-inside anterior cruciate ligament reconstruction: a biomechanical study in a porcine model. Am J Sports Med. 2009;37(1):160-167.
4. Howell SM, Hull ML. Aggressive rehabilitation using hamstring tendons: graft construct, tibial tunnel placement, fixation properties, and clinical outcome. Am J Knee Surg. 1998;11(2):120-127.
5. Magen HE, Howell SM, Hull ML. Structural properties of six tibial fixation methods for anterior cruciate ligament soft tissue grafts. Am J Sports Med. 1999;27(1):35-43.
6. Beynnon BD, Meriam CM, Ryder SH, Fleming BC, Johnson RJ. The effect of screw insertion torque on tendons fixed with spiked washers. Am J Sports Med. 1998;26(4):536-539.
7. Post WR, King SS. Neurovascular risk of bicortical tibial drilling for screw and spiked washer fixation of soft-tissue anterior cruciate ligament graft. Arthroscopy. 2001;17(3):244-247.
8. Holden JP, Grood ES, Butler DL, et al. Biomechanics of fascia lata ligament replacements: early postoperative changes in the goat. J Orthop Res. 1988;6(5):639-647.
9. Rodeo SA, Arnoczky SP, Torzilli PA, Hidaka C, Warren RF. Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am. 1993;75(12):1795-1803.
10. Frank CB, Jackson DW. The science of reconstruction of the anterior cruciate ligament. J Bone Joint Surg Am. 1997;79(10):1556-1576.
11. Markolf KL, Willems MJ, Jackson SR, Finerman GA. In situ calibration of miniature sensors implanted into the anterior cruciate ligament. Part I: strain measurements. J Orthop Res. 1998;16(4):455-463.
12. Kousa P, Teppo LN, Jarvinen TL, Vihavainen M, Kannus P, Jarvinen M. The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction: I. Femoral site. Am J Sports Med. 2003;3 (2)1:174-181.
13. Kousa P, Jarvinen TL, Vihavainen M, Kannus P, Jarvinen M. The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction: II. Tibial site. Am J Sports Med. 2003;31(2):182-188.
14. Brand JC Jr, Pienkowski D, Steenlage E, Hamilton D, Johnson DL, Caborn DN. Interference screw fixation strength of a quadrupled hamstring tendon graft is directly related to bone mineral density and insertion torque. Am J Sports Med. 2000;28(5):705-710.
15. Weiler A, Hoffmann RF, Siepe CJ, Kolbeck SF, Südkamp NP. The influence of screw geometry on hamstring tendon interference fit fixation. Am J Sports Med. 2000;28(3):356-359.
16. Weiler A, Hoffmann RF, Stähelin AC, Bail HJ, Siepe CJ, Südkamp NP. Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone. Arthroscopy. 1998;14(1):29-37.
17. Streich NA, Reichenbacher S, Barié A, Buchner M, Schmitt H. Long-term outcome of anterior cruciate ligament reconstruction with an autologous four-strand semitendinosus tendon autograft. Int Orthop. 2013;37(2):279-284.
18. Barber FA, Herbert MA, Beavis C, Barrera Oro F. Suture anchor materials, eyelets, and designs: update 2008. Arthroscopy. 2008;24(8):859-867.
19. Aickin M, Gensler H. Adjusting for multiple testing when reporting research results: the Bonferroni vs Holm methods. Am J Public Health. 1996;86(5):726-728.
20. Howell SM, Deutsch ML. Comparison of endoscopic and two-incision techniques for reconstructing a torn anterior cruciate ligament using hamstring tendons. Arthroscopy. 1999;15(6):594-606.
21. Gwynne-Jones DP, Draffin J, Vane A, Craig R, McMahon S. Failure strengths of concentric and eccentric implants for hamstring graft fixation. ANZ J Surg. 2008;78(3):177-181.
22. Hayes DA, Watts MC, Tevelen GA, Crawford RW. Central versus peripheral tibial screw placement in hamstring anterior cruciate ligament reconstruction: in vitro biomechanics. Arthroscopy. 2005;21(6):703-706.
23. Shino K, Pflaster DS. Comparison of eccentric and concentric screw placement for hamstring graft fixation in the tibial tunnel. Knee Surg Sports Traumatol Arthrosc. 2000;8(2):73-75.
24. Prevrhal S, Fuerst T, Fan B, et al. Quantitative ultrasound of the tibia depends on both cortical density and thickness. Osteoporosis Int. 2001;12(1):28-34.
25. Pietschmann MF, Gülecyüz MF, Fieseler S, et al. Biomechanical stability of knotless suture anchors used in rotator cuff repair in healthy and osteopenic bone. Arthroscopy. 2010;26(8):1035-1044.
26. Burns JP, Snyder SJ, Albritton M. Arthroscopic rotator cuff repair using triple-loaded anchors, suture shuttles, and suture savers. J Am Acad Orthop Surg. 2007;15(7):432-444.
27. Tetsumura S, Fujita A, Nakajima M, Abe M. Biomechanical comparison of different fixation methods on the tibial side in anterior cruciate ligament reconstruction: a biomechanical study in porcine tibial bone. J Orthop Sci. 2006;11(3):278-282.
28. Alfredson H, Nordstrom P, Lorentzon R. Total and regional bone mass in female soccer players. Calcif Tissue Int. 1996;59(6):438-442.
29. Nevill AM, Holder RL, Stewart AD. Modeling elite male athletes’ peripheral bone mass, assessed using regional dual x-ray absorptiometry. Bone. 2003;32(1):62-68.
30. Nordström P, Lorentzon R. Site-specific bone mass differences of the lower extremities in 17-year-old ice hockey players. Calcif Tissue Int. 1996;59(6):4443-4448.
31. Patzer T, Santo G, Olender GD, Wellmann M, Hurschler C, Schofer MD. Suprapectoral or subpectoral position for biceps tenodesis: biomechanical comparison of four different techniques in both positions. J Shoulder Elbow Surg. 2012;21(1):116-125.
32. De Wall M, Scholes CJ, Patel S, Coolican MR, Parker DA. Tibial fixation in anterior cruciate ligament reconstruction: a prospective randomized study comparing metal interference screw and staples with a centrally placed polyethylene screw and sheath. Am J Sports Med. 2011;39(9):1858-1864.
1. Wetzler MJ, Bartolozzi AR, Gillespie MJ, Rubenstein DL, Ciccotti MG, Miller LS. Revision anterior cruciate ligament reconstruction. Oper Tech Orthop. 1996;6(3):181-189.
2. Scheffler SU, Südkamp NP, Göckenjan A, Hoffmann RF, Weiler A. Biomechanical comparison of hamstring and patellar tendon graft anterior cruciate ligament reconstruction techniques: the impact of fixation level and fixation method under cyclic loading. Arthroscopy. 2002;18(3):304-315.
3. Walsh MP, Wijdicks CA, Parker JB, Hapa O, LaPrade RF. A comparison between a retrograde interference screw, suture button, and combined fixation on the tibial side in an all-inside anterior cruciate ligament reconstruction: a biomechanical study in a porcine model. Am J Sports Med. 2009;37(1):160-167.
4. Howell SM, Hull ML. Aggressive rehabilitation using hamstring tendons: graft construct, tibial tunnel placement, fixation properties, and clinical outcome. Am J Knee Surg. 1998;11(2):120-127.
5. Magen HE, Howell SM, Hull ML. Structural properties of six tibial fixation methods for anterior cruciate ligament soft tissue grafts. Am J Sports Med. 1999;27(1):35-43.
6. Beynnon BD, Meriam CM, Ryder SH, Fleming BC, Johnson RJ. The effect of screw insertion torque on tendons fixed with spiked washers. Am J Sports Med. 1998;26(4):536-539.
7. Post WR, King SS. Neurovascular risk of bicortical tibial drilling for screw and spiked washer fixation of soft-tissue anterior cruciate ligament graft. Arthroscopy. 2001;17(3):244-247.
8. Holden JP, Grood ES, Butler DL, et al. Biomechanics of fascia lata ligament replacements: early postoperative changes in the goat. J Orthop Res. 1988;6(5):639-647.
9. Rodeo SA, Arnoczky SP, Torzilli PA, Hidaka C, Warren RF. Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am. 1993;75(12):1795-1803.
10. Frank CB, Jackson DW. The science of reconstruction of the anterior cruciate ligament. J Bone Joint Surg Am. 1997;79(10):1556-1576.
11. Markolf KL, Willems MJ, Jackson SR, Finerman GA. In situ calibration of miniature sensors implanted into the anterior cruciate ligament. Part I: strain measurements. J Orthop Res. 1998;16(4):455-463.
12. Kousa P, Teppo LN, Jarvinen TL, Vihavainen M, Kannus P, Jarvinen M. The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction: I. Femoral site. Am J Sports Med. 2003;3 (2)1:174-181.
13. Kousa P, Jarvinen TL, Vihavainen M, Kannus P, Jarvinen M. The fixation strength of six hamstring tendon graft fixation devices in anterior cruciate ligament reconstruction: II. Tibial site. Am J Sports Med. 2003;31(2):182-188.
14. Brand JC Jr, Pienkowski D, Steenlage E, Hamilton D, Johnson DL, Caborn DN. Interference screw fixation strength of a quadrupled hamstring tendon graft is directly related to bone mineral density and insertion torque. Am J Sports Med. 2000;28(5):705-710.
15. Weiler A, Hoffmann RF, Siepe CJ, Kolbeck SF, Südkamp NP. The influence of screw geometry on hamstring tendon interference fit fixation. Am J Sports Med. 2000;28(3):356-359.
16. Weiler A, Hoffmann RF, Stähelin AC, Bail HJ, Siepe CJ, Südkamp NP. Hamstring tendon fixation using interference screws: a biomechanical study in calf tibial bone. Arthroscopy. 1998;14(1):29-37.
17. Streich NA, Reichenbacher S, Barié A, Buchner M, Schmitt H. Long-term outcome of anterior cruciate ligament reconstruction with an autologous four-strand semitendinosus tendon autograft. Int Orthop. 2013;37(2):279-284.
18. Barber FA, Herbert MA, Beavis C, Barrera Oro F. Suture anchor materials, eyelets, and designs: update 2008. Arthroscopy. 2008;24(8):859-867.
19. Aickin M, Gensler H. Adjusting for multiple testing when reporting research results: the Bonferroni vs Holm methods. Am J Public Health. 1996;86(5):726-728.
20. Howell SM, Deutsch ML. Comparison of endoscopic and two-incision techniques for reconstructing a torn anterior cruciate ligament using hamstring tendons. Arthroscopy. 1999;15(6):594-606.
21. Gwynne-Jones DP, Draffin J, Vane A, Craig R, McMahon S. Failure strengths of concentric and eccentric implants for hamstring graft fixation. ANZ J Surg. 2008;78(3):177-181.
22. Hayes DA, Watts MC, Tevelen GA, Crawford RW. Central versus peripheral tibial screw placement in hamstring anterior cruciate ligament reconstruction: in vitro biomechanics. Arthroscopy. 2005;21(6):703-706.
23. Shino K, Pflaster DS. Comparison of eccentric and concentric screw placement for hamstring graft fixation in the tibial tunnel. Knee Surg Sports Traumatol Arthrosc. 2000;8(2):73-75.
24. Prevrhal S, Fuerst T, Fan B, et al. Quantitative ultrasound of the tibia depends on both cortical density and thickness. Osteoporosis Int. 2001;12(1):28-34.
25. Pietschmann MF, Gülecyüz MF, Fieseler S, et al. Biomechanical stability of knotless suture anchors used in rotator cuff repair in healthy and osteopenic bone. Arthroscopy. 2010;26(8):1035-1044.
26. Burns JP, Snyder SJ, Albritton M. Arthroscopic rotator cuff repair using triple-loaded anchors, suture shuttles, and suture savers. J Am Acad Orthop Surg. 2007;15(7):432-444.
27. Tetsumura S, Fujita A, Nakajima M, Abe M. Biomechanical comparison of different fixation methods on the tibial side in anterior cruciate ligament reconstruction: a biomechanical study in porcine tibial bone. J Orthop Sci. 2006;11(3):278-282.
28. Alfredson H, Nordstrom P, Lorentzon R. Total and regional bone mass in female soccer players. Calcif Tissue Int. 1996;59(6):438-442.
29. Nevill AM, Holder RL, Stewart AD. Modeling elite male athletes’ peripheral bone mass, assessed using regional dual x-ray absorptiometry. Bone. 2003;32(1):62-68.
30. Nordström P, Lorentzon R. Site-specific bone mass differences of the lower extremities in 17-year-old ice hockey players. Calcif Tissue Int. 1996;59(6):4443-4448.
31. Patzer T, Santo G, Olender GD, Wellmann M, Hurschler C, Schofer MD. Suprapectoral or subpectoral position for biceps tenodesis: biomechanical comparison of four different techniques in both positions. J Shoulder Elbow Surg. 2012;21(1):116-125.
32. De Wall M, Scholes CJ, Patel S, Coolican MR, Parker DA. Tibial fixation in anterior cruciate ligament reconstruction: a prospective randomized study comparing metal interference screw and staples with a centrally placed polyethylene screw and sheath. Am J Sports Med. 2011;39(9):1858-1864.
Dilute Betadine Lavage Reduces Implant-Related Bacterial Burden in a Rabbit Knee Prosthetic Infection Model
Surgical site infection after arthroplasty causes substantial morbidity and potential mortality. Prosthetic joint infection (PJI) ranges from simple superficial wound infection and cellulitis to deep subfascial infection that involves the prosthesis. Consistent use of prophylactic antibiotics has reduced postoperative hip and knee arthroplasty infections to rates of 0.25% to 2%.1-4 Treatment of a patient with PJI commonly includes hospitalization, long-term intravenously administered antibiotics, resection arthroplasty, and staged reimplantation. The estimated cost of interventions reaches tens of millions of dollars annually in the United States and does not include the costs of psychosocial effects on patients and their families.5,6
Betadine (povidone-iodine) is a widely used antiseptic for skin and mucous membrane wounds and has been shown to be effective for the prevention of PJI.7 Dilute Betadine solution has been proposed as an aid in treatment of PJI.8 At a minimum concentration of 5%, cytotoxicity has been observed in chicken tibia osteoblasts.9 A balance of the bactericidal and cytotoxic activities of Betadine, while maintaining its efficacy against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), is optimized at dilutions between 0.5% and 4%.10-14 We hypothesized that a dilute Betadine lavage of 3.5% would achieve a significant decrease in bacterial counts compared with an isolated saline lavage in an in vivo knee PJI model.
Materials and Methods
Animal Protocol
All surgical procedures were conducted according to the protocol approved by our institutional animal care and use committee. Using a power analysis and data obtained at our institution, we determined that 12 was the minimum number of animals needed to reach significance set at P < .05 and assuming a 50% decrease in colony-forming units (CFU) (SigmaStat Version 2.03; Aspire Software International, Ashburn, Virginia). Eight New Zealand White rabbits were used in our study; because significance was reached early, 12 were not needed. The average weight of the rabbits was 3.5 kg (weight range, 3.2-4.1 kg). All rabbits completed 1 week of acclimation before surgery.
Bacteria Preparation
A broth culture of methicillin-sensitive S aureus (MSSA) (ATCC 25923) was prepared 1 day before surgery. The bacteria were suspended in 5 mL of Trypticase Soy Broth (Becton Dickinson & Co, Franklin Lakes, New Jersey) and incubated at 37°C in a shaking incubator for 16 hours. The next day, the culture was centrifuged and irrigated twice with normal saline to remove the broth and prevent further growth. The bacteria were reconstituted in normal saline, and the concentration was standardized using a turbidity meter (LaMotte 2020e; LaMotte Co, Chestertown, Maryland), which correlated with 106 CFU/100 µl plated on trypticase soy agar plates with 10% sheep blood (Fisher Scientific, Pittsburgh, Pennsylvania).
Surgical and Postoperative Procedures
Our procedure was based on the New Zealand White rabbit knee PJI model.15 General anesthesia was induced with ketamine and xylazine, and maintained with isoflurane inhalation via a nose cone mask. Rabbits were positioned supine, and bilateral knees were shaved, prepped, and draped in a sterile fashion.
A 2-cm longitudinal incision was made over the lateral knee, and arthrotomy was performed, exposing the lateral collateral ligament attachment at the lateral femoral condyle. Using a 4-mm drill bit, a defect was drilled obliquely into the lateral femoral condyle, anterior to the lateral collateral ligament attachment. This produced a defect in the non-weight-bearing, nonarticulating portion of the knee. A fully threaded 4×14-mm stainless steel screw (Synthes, West Chester, Pennsylvania) with a U-shaped ultrahigh-molecular-weight polyethylene washer (Synthes) was inserted into the defect. The joint capsule was closed with a running 3-0 Vicryl suture (Ethicon, Somerville, New Jersey). The knee joint was inoculated with 100 µL of the S aureus preparation using a 22-gauge needle. The skin was closed with a 4-0 Biosyn suture (Ethicon). The procedure was repeated on the contralateral knee (Figures 1A, 1B).
Seven days after the initial surgery, the rabbits were returned to the operating room and were anesthetized, positioned, and prepped for surgery as detailed above. Ceftriaxone (20 mg/kg of body weight) was intravenously administered to all rabbits for the treatment procedure. For each rabbit, a control knee and an experimental knee were randomly assigned. A longitudinal incision was made, exposing the previously placed implants. The screw was loosened slightly to remove the U-shaped polyethylene washer. Each knee then underwent lavage 2 times, for 90 seconds each time, with 3.5% dilute Betadine solution (experimental knee) or with normal saline (control knee). Because Pseudomonas contamination has been reported with povidone-iodine taken from unsterilized bottles,16,17 packets of sterilized povidone-iodine (Aplicare; Clorox, Oakland, California) were used. After the irrigation was complete, a new sterile polyethylene washer was placed and the screw was tightened. The wound closure was repeated as detailed above.
Postoperative analgesia was provided based on a standard institutional animal care and use committee protocol. Rabbits were permitted full cage activity and nutrition ad libitum. Wound healing, body weight, and signs of distress were monitored daily.
Outcome Measures
Seven days after surgery, the rabbits were euthanized with administration of phenobarbital (100 mg/kg of body weight). Arterial blood samples were obtained from the auricular vein to ensure that the rabbits were not systemically infected. Using a sterile technique, the screw, polyethylene washer, lateral femoral condyle bone from the defect, and joint capsule were cultured. Harvested bone and soft tissues were weighed and immediately homogenized (PowerGen Model 35 Handheld Homogenizer; Thermo Fisher Scientific, Inc, Waltham, Massachusetts). Implants were sonicated (UBATH-Y; World Precision Instruments, Inc, Sarasota, Florida) in cold saline to obtain a sensitive culture.18
Bacterial quantification was determined by using trypticase soy agar plates after 24 hours of growth. Final CFU were calculated after serial dilutions and were standardized per gram of biopsied tissues.19 Members of the team were blinded to the treatment type.
Statistical Analysis
Statistical differences in mean bacterial burden were calculated independently for lateral condyle bone, joint capsule, polyethylene, and screws by conducting a Student t test.
Results
Treatment effect was higher than expected, and the study was terminated after 8 animals completed the protocol. All 8 rabbits tolerated the procedures well and were appropriately monitored during the postoperative period. No animals had signs of systemic infection or positive blood culture. All local cultures for screw, polyethylene washer, lateral femoral condyle defect, and joint capsule were positive.
Statistically significant decreases were shown in the bacterial burden of the Betadine-irrigated screws and the Betadine-irrigated polyethylene washers compared with the saline-irrigated controls. Betadine-irrigated screws grew an average of 7.16 × 101 CFU of S aureus/g, whereas screws from control knees grew an average of 1.45 × 103 CFU/g (P = .0003) (Figure 2). Betadine-treated washers grew an average of 1.28 × 103 CFU/g compared with 1.62 × 104 CFU/g for control washers (P =. 04) (Figure 3).
A trend toward decreased bacterial counts was shown in Betadine-treated soft tissues compared with saline-treated soft tissues, but the difference did not reach statistical significance (P = .9). Biopsied joint capsule from knees treated with Betadine grew an average of 2.84 × 104 CFU/g compared with an average of 3.16 × 104 CFU/g in control-rabbit knees (Figure 4). Cultured lateral condyle from Betadine-treated knees had an average bacterial load of 3.22 × 104 CFU/g compared with an average bacterial load of 1 × 105 CFU/g in control knees (Figure 4).
Discussion
Knees irrigated with Betadine showed a significant (P = .0003) decrease in metal implant–related S aureus bacterial counts by 20-fold and a significant (P < .05) decrease in polyethylene implant–related counts by more than 10-fold. This arthroplasty model used Betadine lavage as a treatment adjunct with intravenously administered antibiotics and polyethylene exchange. Our 1-week interval after the index procedure classifies the infection as an acute postoperative arthroplasty infection (occurring less than 4 weeks postoperatively).
The gold standard treatment for these infections is irrigation and débridement with component retention.18 The success rate has been reported to be as high as 71%20 but was closer to 44% in a study by Fridkin and colleagues,21 especially with more virulent bacteria. Staphylococcal species, higher American Society of Anesthesiologists scores, and frank pus around the prosthesis were markers of débridement failure in a recent study by Azzam and colleagues.18
The majority of postoperative joint arthroplasty infections are caused by S aureus, and the incidence of MRSA bacteria continues to rise.22 Community-acquired MRSA is increasing at an alarming rate and is now the predominant organism in skin and soft-tissue infections.23 Organism resistance also occurs at a cellular level by the formation of a glycocalyx layer, or biofilm. This layer assists in changing the phenotypic properties of the organism and decreases the efficacy of antibiotics.24 The self-produced layer of extracellular matrices, deoxyribonucleic acid, and polysaccharides attaches to inert material, preventing phagocytic action by neutrophils. In addition to antibacterial activity, povidone-iodine has antibiofilm activity against Staphylococcal species.25 The active ingredient targets the gene that produces biofilm. This correlates to our study in which the largest decrease in bacterial counts was noted on the implants.
The use of Betadine lavage has shown some promise in vivo as well. A prospective randomized controlled trial26 used 3.5% Betadine irrigation to prevent spine infection. No infections occurred in the Betadine group compared with a deep-infection rate of 2.9% in the control group. Brown and colleagues8 reviewed 1862 hip and knee arthroplasty cases before the use of Betadine lavage and 688 cases after the use of Betadine lavage and found a decrease in infection rate, from 0.97% to 0.15%. S aureus caused 13 of the 18 infections in the control group. These studies8,26 used Betadine lavage for prophylaxis and prevention of deep spine and arthroplasty infection. Betadine lavage as a treatment adjunct for acute arthroplasty infection has not been studied clinically. It has the potential to increase isolated incision and débridement success and to improve component survivorship.
Our arthroplasty model mimics an intra-articular environment and accounts for an implant–polyethylene interface.15 Limitations of our study include the use of MSSA as opposed to MRSA. However, povidone-iodine has the same effects on both MSSA and MRSA.12 We also treated our postoperative infection with 1 dose of antibiotics and not a course, although it should be noted that the single dose of ceftriaxone allowed us to isolate the independent effect of the Betadine lavage. A baseline level of infection severity could have been measured with cultures obtained at the time of irrigation and débridement. Also, a decrease in CFU does not directly correlate to a clinically significant outcome, such as a defined surgical site infection requiring intervention. Nevertheless, it is noteworthy that the decrease in bacterial counts on the stainless steel screws and polyethylene washers were maintained 1 week after the Betadine lavage.
Conclusion
Dilute Betadine lavage is a simple and inexpensive adjunct for the treatment of acute postoperative arthroplasty infection and may increase the rate of component retention. Additionally, the bactericidal and antibiofilm activities of Betadine may improve the effectiveness of systemic antibiotics. Further clinical investigation is warranted.
1. Wilson MG, Kelley K, Thornhill TS. Infection as a complication of total knee-replacement arthroplasty. Risk factors and treatment in sixty-seven cases. J Bone Joint Surg Am. 1990;72(6):878-883.
2. Ridgeway S, Wilson J, Charlet A, Kafatos G, Pearson A, Coello R. Infection of the surgical site after arthroplasty of the hip. J Bone Joint Surg Br. 2005;87(6):844-850.
3. Mahomed NN, Barrett JA, Katz JN, et al. Rates and outcomes of primary and revision total hip replacement in the United States medicare population. J Bone Joint Surg Am. 2003;85(1):27-32.
4. Mahomed NN, Barrett J, Katz JN, Baron JA, Wright J, Losina E. Epidemiology of total knee replacement in the United States Medicare population. J Bone Joint Surg Am. 2005;87(6):1222-1228.
5. Parvizi J, Zmistowski B, Adeli B. Periprosthetic joint infection: treatment options. Orthopedics. 2010;33(9):659.
6. Poultsides LA, Liaropoulos LL, Malizos KN. The socioeconomic impact of musculoskeletal infections. J Bone Joint Surg Am. 2010;92(11):e13.
7. Chundamala J, Wright JG. The efficacy and risks of using povidone-iodine irrigation to prevent surgical site infection: an evidence-based review. Can J Surg. 2007;50(6):473-481.
8. Brown NM, Cipriano CA, Moric M, Sporer SM, Della Valle CJ. Dilute betadine lavage before closure for the prevention of acute postoperative deep periprosthetic joint infection. J Arthroplasty. 2012;27(1):27-30.
9. Kaysinger KK, Nicholson NC, Ramp WK, Kellam JF. Toxic effects of wound irrigation solutions on cultured tibiae and osteoblasts. J Orthop Trauma. 1995;9(4):303-311.
10. Haley CE, Marling-Cason M, Smith JW, Luby JP, Mackowiak PA. Bactericidal activity of antiseptics against methicillin-resistant Staphylococcus aureus. J Clin Microbiol. 1985;21(6):991-992.
11. Lacey RW, Catto A. Action of povidone-iodine against methicillin-sensitive and -resistant cultures of Staphylococcus aureus. Postgrad Med J. 1993;69(3 suppl):S78-S83.
12. McLure AR, Gordon J. In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus aureus. J Hosp Infect. 1992;21(4):291-299.
13. Suzuki J, Komatsuzawa H, Kozai K, Nagasaka N. In vitro susceptibility of Staphylococcus aureus including MRSA to four disinfectants. ASDC J Dent Child. 1997;64(4):260-263.
14. Yasuda T, Yoshimura S, Katsuno Y, et al. Comparison of bactericidal activities of various disinfectants against methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. Postgrad Med J. 1993;69(3 suppl):S66-S69.
15. Craig MR, Poelstra KA, Sherrell JC, Kwon MS, Belzile EL, Brown TE. A novel total knee arthroplasty infection model in rabbits. J Orthop Res. 2005;23(5):1100-1104.
16. Hartman MB, Fehring TK, Jordan L, Norton HJ. Periprosthetic knee sepsis. The role of irrigation and debridement. Clin Orthop. 1991;273:113-118.
17. Mont MA, Waldman B, Banerjee C, Pacheco IH, Hungerford DS. Multiple irrigation, debridement, and retention of components in infected total knee arthroplasty. J Arthroplasty. 1997;12(4):426-433.
18. Azzam KA, Seeley M, Ghanem E, Austin MS, Purtill JJ, Parvizi J. Irrigation and debridement in the management of prosthetic joint infection: traditional indications revisited. J Arthroplasty. 2010;25(7):1022-1027.
19. Stall AC, Becker E, Ludwig SC, Gelb D, Poelstra KA. Reduction of postoperative spinal implant infection using gentamicin microspheres. Spine (Phila Pa 1976). 2009;34(5):479-483.
20. Hota B, Ellenbogen C, Hayden MK, Aroutcheva A, Rice TW, Weinstein RA. Community-associated methicillin-resistant Staphylococcus aureus skin and soft tissue infections at a public hospital: do public housing and incarceration amplify transmission? Arch Intern Med. 2007;167(10):1026-1033.
21. Fridkin SK, Hageman JC, Morrison M, et al, Active Bacterial Core Surveillance Program of the Emerging Infections Program Network. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med. 2005;352(14):1436-1444.
22. Hosman AH, van der Mei HC, Bulstra SK, Busscher HJ, Neut D. Metal-on-metal bearings in total hip arthroplasties: influence of cobalt and chromium ions on bacterial growth and biofilm formation. J Biomed Mater Res A. 2009;88(3):711-716.
23. Oduwole KO, Glynn AA, Molony DC, et al. Anti-biofilm activity of sub-inhibitory povidone-iodine concentrations against Staphylococcus epidermidis and Staphylococcus aureus. J Orthop Res. 2010;28(9):1252-1256.
24. Cheng MT, Chang MC, Wang ST, Yu WK, Liu CL, Chen TH. Efficacy of dilute betadine solution irrigation in the prevention of postoperative infection of spinal surgery. Spine (Phila Pa 1976). 2005;30(15):1689-1693.
25. Anderson RL, Vess RW, Panlilio AL, Favero MS. Prolonged survival of Pseudomonas cepacia in commercially manufactured povidone-iodine. Appl Environ Microbiol. 1990;56(11):3598-3600.
26. Panlilio AL, Beck-Sague CM, Siegel JD, et al. Infections and pseudoinfections due to povidone-iodine solution contaminated with Pseudomonas cepacia. Clin Infect Dis. 1992;14(5):1078-1083.
Surgical site infection after arthroplasty causes substantial morbidity and potential mortality. Prosthetic joint infection (PJI) ranges from simple superficial wound infection and cellulitis to deep subfascial infection that involves the prosthesis. Consistent use of prophylactic antibiotics has reduced postoperative hip and knee arthroplasty infections to rates of 0.25% to 2%.1-4 Treatment of a patient with PJI commonly includes hospitalization, long-term intravenously administered antibiotics, resection arthroplasty, and staged reimplantation. The estimated cost of interventions reaches tens of millions of dollars annually in the United States and does not include the costs of psychosocial effects on patients and their families.5,6
Betadine (povidone-iodine) is a widely used antiseptic for skin and mucous membrane wounds and has been shown to be effective for the prevention of PJI.7 Dilute Betadine solution has been proposed as an aid in treatment of PJI.8 At a minimum concentration of 5%, cytotoxicity has been observed in chicken tibia osteoblasts.9 A balance of the bactericidal and cytotoxic activities of Betadine, while maintaining its efficacy against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), is optimized at dilutions between 0.5% and 4%.10-14 We hypothesized that a dilute Betadine lavage of 3.5% would achieve a significant decrease in bacterial counts compared with an isolated saline lavage in an in vivo knee PJI model.
Materials and Methods
Animal Protocol
All surgical procedures were conducted according to the protocol approved by our institutional animal care and use committee. Using a power analysis and data obtained at our institution, we determined that 12 was the minimum number of animals needed to reach significance set at P < .05 and assuming a 50% decrease in colony-forming units (CFU) (SigmaStat Version 2.03; Aspire Software International, Ashburn, Virginia). Eight New Zealand White rabbits were used in our study; because significance was reached early, 12 were not needed. The average weight of the rabbits was 3.5 kg (weight range, 3.2-4.1 kg). All rabbits completed 1 week of acclimation before surgery.
Bacteria Preparation
A broth culture of methicillin-sensitive S aureus (MSSA) (ATCC 25923) was prepared 1 day before surgery. The bacteria were suspended in 5 mL of Trypticase Soy Broth (Becton Dickinson & Co, Franklin Lakes, New Jersey) and incubated at 37°C in a shaking incubator for 16 hours. The next day, the culture was centrifuged and irrigated twice with normal saline to remove the broth and prevent further growth. The bacteria were reconstituted in normal saline, and the concentration was standardized using a turbidity meter (LaMotte 2020e; LaMotte Co, Chestertown, Maryland), which correlated with 106 CFU/100 µl plated on trypticase soy agar plates with 10% sheep blood (Fisher Scientific, Pittsburgh, Pennsylvania).
Surgical and Postoperative Procedures
Our procedure was based on the New Zealand White rabbit knee PJI model.15 General anesthesia was induced with ketamine and xylazine, and maintained with isoflurane inhalation via a nose cone mask. Rabbits were positioned supine, and bilateral knees were shaved, prepped, and draped in a sterile fashion.
A 2-cm longitudinal incision was made over the lateral knee, and arthrotomy was performed, exposing the lateral collateral ligament attachment at the lateral femoral condyle. Using a 4-mm drill bit, a defect was drilled obliquely into the lateral femoral condyle, anterior to the lateral collateral ligament attachment. This produced a defect in the non-weight-bearing, nonarticulating portion of the knee. A fully threaded 4×14-mm stainless steel screw (Synthes, West Chester, Pennsylvania) with a U-shaped ultrahigh-molecular-weight polyethylene washer (Synthes) was inserted into the defect. The joint capsule was closed with a running 3-0 Vicryl suture (Ethicon, Somerville, New Jersey). The knee joint was inoculated with 100 µL of the S aureus preparation using a 22-gauge needle. The skin was closed with a 4-0 Biosyn suture (Ethicon). The procedure was repeated on the contralateral knee (Figures 1A, 1B).
Seven days after the initial surgery, the rabbits were returned to the operating room and were anesthetized, positioned, and prepped for surgery as detailed above. Ceftriaxone (20 mg/kg of body weight) was intravenously administered to all rabbits for the treatment procedure. For each rabbit, a control knee and an experimental knee were randomly assigned. A longitudinal incision was made, exposing the previously placed implants. The screw was loosened slightly to remove the U-shaped polyethylene washer. Each knee then underwent lavage 2 times, for 90 seconds each time, with 3.5% dilute Betadine solution (experimental knee) or with normal saline (control knee). Because Pseudomonas contamination has been reported with povidone-iodine taken from unsterilized bottles,16,17 packets of sterilized povidone-iodine (Aplicare; Clorox, Oakland, California) were used. After the irrigation was complete, a new sterile polyethylene washer was placed and the screw was tightened. The wound closure was repeated as detailed above.
Postoperative analgesia was provided based on a standard institutional animal care and use committee protocol. Rabbits were permitted full cage activity and nutrition ad libitum. Wound healing, body weight, and signs of distress were monitored daily.
Outcome Measures
Seven days after surgery, the rabbits were euthanized with administration of phenobarbital (100 mg/kg of body weight). Arterial blood samples were obtained from the auricular vein to ensure that the rabbits were not systemically infected. Using a sterile technique, the screw, polyethylene washer, lateral femoral condyle bone from the defect, and joint capsule were cultured. Harvested bone and soft tissues were weighed and immediately homogenized (PowerGen Model 35 Handheld Homogenizer; Thermo Fisher Scientific, Inc, Waltham, Massachusetts). Implants were sonicated (UBATH-Y; World Precision Instruments, Inc, Sarasota, Florida) in cold saline to obtain a sensitive culture.18
Bacterial quantification was determined by using trypticase soy agar plates after 24 hours of growth. Final CFU were calculated after serial dilutions and were standardized per gram of biopsied tissues.19 Members of the team were blinded to the treatment type.
Statistical Analysis
Statistical differences in mean bacterial burden were calculated independently for lateral condyle bone, joint capsule, polyethylene, and screws by conducting a Student t test.
Results
Treatment effect was higher than expected, and the study was terminated after 8 animals completed the protocol. All 8 rabbits tolerated the procedures well and were appropriately monitored during the postoperative period. No animals had signs of systemic infection or positive blood culture. All local cultures for screw, polyethylene washer, lateral femoral condyle defect, and joint capsule were positive.
Statistically significant decreases were shown in the bacterial burden of the Betadine-irrigated screws and the Betadine-irrigated polyethylene washers compared with the saline-irrigated controls. Betadine-irrigated screws grew an average of 7.16 × 101 CFU of S aureus/g, whereas screws from control knees grew an average of 1.45 × 103 CFU/g (P = .0003) (Figure 2). Betadine-treated washers grew an average of 1.28 × 103 CFU/g compared with 1.62 × 104 CFU/g for control washers (P =. 04) (Figure 3).
A trend toward decreased bacterial counts was shown in Betadine-treated soft tissues compared with saline-treated soft tissues, but the difference did not reach statistical significance (P = .9). Biopsied joint capsule from knees treated with Betadine grew an average of 2.84 × 104 CFU/g compared with an average of 3.16 × 104 CFU/g in control-rabbit knees (Figure 4). Cultured lateral condyle from Betadine-treated knees had an average bacterial load of 3.22 × 104 CFU/g compared with an average bacterial load of 1 × 105 CFU/g in control knees (Figure 4).
Discussion
Knees irrigated with Betadine showed a significant (P = .0003) decrease in metal implant–related S aureus bacterial counts by 20-fold and a significant (P < .05) decrease in polyethylene implant–related counts by more than 10-fold. This arthroplasty model used Betadine lavage as a treatment adjunct with intravenously administered antibiotics and polyethylene exchange. Our 1-week interval after the index procedure classifies the infection as an acute postoperative arthroplasty infection (occurring less than 4 weeks postoperatively).
The gold standard treatment for these infections is irrigation and débridement with component retention.18 The success rate has been reported to be as high as 71%20 but was closer to 44% in a study by Fridkin and colleagues,21 especially with more virulent bacteria. Staphylococcal species, higher American Society of Anesthesiologists scores, and frank pus around the prosthesis were markers of débridement failure in a recent study by Azzam and colleagues.18
The majority of postoperative joint arthroplasty infections are caused by S aureus, and the incidence of MRSA bacteria continues to rise.22 Community-acquired MRSA is increasing at an alarming rate and is now the predominant organism in skin and soft-tissue infections.23 Organism resistance also occurs at a cellular level by the formation of a glycocalyx layer, or biofilm. This layer assists in changing the phenotypic properties of the organism and decreases the efficacy of antibiotics.24 The self-produced layer of extracellular matrices, deoxyribonucleic acid, and polysaccharides attaches to inert material, preventing phagocytic action by neutrophils. In addition to antibacterial activity, povidone-iodine has antibiofilm activity against Staphylococcal species.25 The active ingredient targets the gene that produces biofilm. This correlates to our study in which the largest decrease in bacterial counts was noted on the implants.
The use of Betadine lavage has shown some promise in vivo as well. A prospective randomized controlled trial26 used 3.5% Betadine irrigation to prevent spine infection. No infections occurred in the Betadine group compared with a deep-infection rate of 2.9% in the control group. Brown and colleagues8 reviewed 1862 hip and knee arthroplasty cases before the use of Betadine lavage and 688 cases after the use of Betadine lavage and found a decrease in infection rate, from 0.97% to 0.15%. S aureus caused 13 of the 18 infections in the control group. These studies8,26 used Betadine lavage for prophylaxis and prevention of deep spine and arthroplasty infection. Betadine lavage as a treatment adjunct for acute arthroplasty infection has not been studied clinically. It has the potential to increase isolated incision and débridement success and to improve component survivorship.
Our arthroplasty model mimics an intra-articular environment and accounts for an implant–polyethylene interface.15 Limitations of our study include the use of MSSA as opposed to MRSA. However, povidone-iodine has the same effects on both MSSA and MRSA.12 We also treated our postoperative infection with 1 dose of antibiotics and not a course, although it should be noted that the single dose of ceftriaxone allowed us to isolate the independent effect of the Betadine lavage. A baseline level of infection severity could have been measured with cultures obtained at the time of irrigation and débridement. Also, a decrease in CFU does not directly correlate to a clinically significant outcome, such as a defined surgical site infection requiring intervention. Nevertheless, it is noteworthy that the decrease in bacterial counts on the stainless steel screws and polyethylene washers were maintained 1 week after the Betadine lavage.
Conclusion
Dilute Betadine lavage is a simple and inexpensive adjunct for the treatment of acute postoperative arthroplasty infection and may increase the rate of component retention. Additionally, the bactericidal and antibiofilm activities of Betadine may improve the effectiveness of systemic antibiotics. Further clinical investigation is warranted.
Surgical site infection after arthroplasty causes substantial morbidity and potential mortality. Prosthetic joint infection (PJI) ranges from simple superficial wound infection and cellulitis to deep subfascial infection that involves the prosthesis. Consistent use of prophylactic antibiotics has reduced postoperative hip and knee arthroplasty infections to rates of 0.25% to 2%.1-4 Treatment of a patient with PJI commonly includes hospitalization, long-term intravenously administered antibiotics, resection arthroplasty, and staged reimplantation. The estimated cost of interventions reaches tens of millions of dollars annually in the United States and does not include the costs of psychosocial effects on patients and their families.5,6
Betadine (povidone-iodine) is a widely used antiseptic for skin and mucous membrane wounds and has been shown to be effective for the prevention of PJI.7 Dilute Betadine solution has been proposed as an aid in treatment of PJI.8 At a minimum concentration of 5%, cytotoxicity has been observed in chicken tibia osteoblasts.9 A balance of the bactericidal and cytotoxic activities of Betadine, while maintaining its efficacy against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), is optimized at dilutions between 0.5% and 4%.10-14 We hypothesized that a dilute Betadine lavage of 3.5% would achieve a significant decrease in bacterial counts compared with an isolated saline lavage in an in vivo knee PJI model.
Materials and Methods
Animal Protocol
All surgical procedures were conducted according to the protocol approved by our institutional animal care and use committee. Using a power analysis and data obtained at our institution, we determined that 12 was the minimum number of animals needed to reach significance set at P < .05 and assuming a 50% decrease in colony-forming units (CFU) (SigmaStat Version 2.03; Aspire Software International, Ashburn, Virginia). Eight New Zealand White rabbits were used in our study; because significance was reached early, 12 were not needed. The average weight of the rabbits was 3.5 kg (weight range, 3.2-4.1 kg). All rabbits completed 1 week of acclimation before surgery.
Bacteria Preparation
A broth culture of methicillin-sensitive S aureus (MSSA) (ATCC 25923) was prepared 1 day before surgery. The bacteria were suspended in 5 mL of Trypticase Soy Broth (Becton Dickinson & Co, Franklin Lakes, New Jersey) and incubated at 37°C in a shaking incubator for 16 hours. The next day, the culture was centrifuged and irrigated twice with normal saline to remove the broth and prevent further growth. The bacteria were reconstituted in normal saline, and the concentration was standardized using a turbidity meter (LaMotte 2020e; LaMotte Co, Chestertown, Maryland), which correlated with 106 CFU/100 µl plated on trypticase soy agar plates with 10% sheep blood (Fisher Scientific, Pittsburgh, Pennsylvania).
Surgical and Postoperative Procedures
Our procedure was based on the New Zealand White rabbit knee PJI model.15 General anesthesia was induced with ketamine and xylazine, and maintained with isoflurane inhalation via a nose cone mask. Rabbits were positioned supine, and bilateral knees were shaved, prepped, and draped in a sterile fashion.
A 2-cm longitudinal incision was made over the lateral knee, and arthrotomy was performed, exposing the lateral collateral ligament attachment at the lateral femoral condyle. Using a 4-mm drill bit, a defect was drilled obliquely into the lateral femoral condyle, anterior to the lateral collateral ligament attachment. This produced a defect in the non-weight-bearing, nonarticulating portion of the knee. A fully threaded 4×14-mm stainless steel screw (Synthes, West Chester, Pennsylvania) with a U-shaped ultrahigh-molecular-weight polyethylene washer (Synthes) was inserted into the defect. The joint capsule was closed with a running 3-0 Vicryl suture (Ethicon, Somerville, New Jersey). The knee joint was inoculated with 100 µL of the S aureus preparation using a 22-gauge needle. The skin was closed with a 4-0 Biosyn suture (Ethicon). The procedure was repeated on the contralateral knee (Figures 1A, 1B).
Seven days after the initial surgery, the rabbits were returned to the operating room and were anesthetized, positioned, and prepped for surgery as detailed above. Ceftriaxone (20 mg/kg of body weight) was intravenously administered to all rabbits for the treatment procedure. For each rabbit, a control knee and an experimental knee were randomly assigned. A longitudinal incision was made, exposing the previously placed implants. The screw was loosened slightly to remove the U-shaped polyethylene washer. Each knee then underwent lavage 2 times, for 90 seconds each time, with 3.5% dilute Betadine solution (experimental knee) or with normal saline (control knee). Because Pseudomonas contamination has been reported with povidone-iodine taken from unsterilized bottles,16,17 packets of sterilized povidone-iodine (Aplicare; Clorox, Oakland, California) were used. After the irrigation was complete, a new sterile polyethylene washer was placed and the screw was tightened. The wound closure was repeated as detailed above.
Postoperative analgesia was provided based on a standard institutional animal care and use committee protocol. Rabbits were permitted full cage activity and nutrition ad libitum. Wound healing, body weight, and signs of distress were monitored daily.
Outcome Measures
Seven days after surgery, the rabbits were euthanized with administration of phenobarbital (100 mg/kg of body weight). Arterial blood samples were obtained from the auricular vein to ensure that the rabbits were not systemically infected. Using a sterile technique, the screw, polyethylene washer, lateral femoral condyle bone from the defect, and joint capsule were cultured. Harvested bone and soft tissues were weighed and immediately homogenized (PowerGen Model 35 Handheld Homogenizer; Thermo Fisher Scientific, Inc, Waltham, Massachusetts). Implants were sonicated (UBATH-Y; World Precision Instruments, Inc, Sarasota, Florida) in cold saline to obtain a sensitive culture.18
Bacterial quantification was determined by using trypticase soy agar plates after 24 hours of growth. Final CFU were calculated after serial dilutions and were standardized per gram of biopsied tissues.19 Members of the team were blinded to the treatment type.
Statistical Analysis
Statistical differences in mean bacterial burden were calculated independently for lateral condyle bone, joint capsule, polyethylene, and screws by conducting a Student t test.
Results
Treatment effect was higher than expected, and the study was terminated after 8 animals completed the protocol. All 8 rabbits tolerated the procedures well and were appropriately monitored during the postoperative period. No animals had signs of systemic infection or positive blood culture. All local cultures for screw, polyethylene washer, lateral femoral condyle defect, and joint capsule were positive.
Statistically significant decreases were shown in the bacterial burden of the Betadine-irrigated screws and the Betadine-irrigated polyethylene washers compared with the saline-irrigated controls. Betadine-irrigated screws grew an average of 7.16 × 101 CFU of S aureus/g, whereas screws from control knees grew an average of 1.45 × 103 CFU/g (P = .0003) (Figure 2). Betadine-treated washers grew an average of 1.28 × 103 CFU/g compared with 1.62 × 104 CFU/g for control washers (P =. 04) (Figure 3).
A trend toward decreased bacterial counts was shown in Betadine-treated soft tissues compared with saline-treated soft tissues, but the difference did not reach statistical significance (P = .9). Biopsied joint capsule from knees treated with Betadine grew an average of 2.84 × 104 CFU/g compared with an average of 3.16 × 104 CFU/g in control-rabbit knees (Figure 4). Cultured lateral condyle from Betadine-treated knees had an average bacterial load of 3.22 × 104 CFU/g compared with an average bacterial load of 1 × 105 CFU/g in control knees (Figure 4).
Discussion
Knees irrigated with Betadine showed a significant (P = .0003) decrease in metal implant–related S aureus bacterial counts by 20-fold and a significant (P < .05) decrease in polyethylene implant–related counts by more than 10-fold. This arthroplasty model used Betadine lavage as a treatment adjunct with intravenously administered antibiotics and polyethylene exchange. Our 1-week interval after the index procedure classifies the infection as an acute postoperative arthroplasty infection (occurring less than 4 weeks postoperatively).
The gold standard treatment for these infections is irrigation and débridement with component retention.18 The success rate has been reported to be as high as 71%20 but was closer to 44% in a study by Fridkin and colleagues,21 especially with more virulent bacteria. Staphylococcal species, higher American Society of Anesthesiologists scores, and frank pus around the prosthesis were markers of débridement failure in a recent study by Azzam and colleagues.18
The majority of postoperative joint arthroplasty infections are caused by S aureus, and the incidence of MRSA bacteria continues to rise.22 Community-acquired MRSA is increasing at an alarming rate and is now the predominant organism in skin and soft-tissue infections.23 Organism resistance also occurs at a cellular level by the formation of a glycocalyx layer, or biofilm. This layer assists in changing the phenotypic properties of the organism and decreases the efficacy of antibiotics.24 The self-produced layer of extracellular matrices, deoxyribonucleic acid, and polysaccharides attaches to inert material, preventing phagocytic action by neutrophils. In addition to antibacterial activity, povidone-iodine has antibiofilm activity against Staphylococcal species.25 The active ingredient targets the gene that produces biofilm. This correlates to our study in which the largest decrease in bacterial counts was noted on the implants.
The use of Betadine lavage has shown some promise in vivo as well. A prospective randomized controlled trial26 used 3.5% Betadine irrigation to prevent spine infection. No infections occurred in the Betadine group compared with a deep-infection rate of 2.9% in the control group. Brown and colleagues8 reviewed 1862 hip and knee arthroplasty cases before the use of Betadine lavage and 688 cases after the use of Betadine lavage and found a decrease in infection rate, from 0.97% to 0.15%. S aureus caused 13 of the 18 infections in the control group. These studies8,26 used Betadine lavage for prophylaxis and prevention of deep spine and arthroplasty infection. Betadine lavage as a treatment adjunct for acute arthroplasty infection has not been studied clinically. It has the potential to increase isolated incision and débridement success and to improve component survivorship.
Our arthroplasty model mimics an intra-articular environment and accounts for an implant–polyethylene interface.15 Limitations of our study include the use of MSSA as opposed to MRSA. However, povidone-iodine has the same effects on both MSSA and MRSA.12 We also treated our postoperative infection with 1 dose of antibiotics and not a course, although it should be noted that the single dose of ceftriaxone allowed us to isolate the independent effect of the Betadine lavage. A baseline level of infection severity could have been measured with cultures obtained at the time of irrigation and débridement. Also, a decrease in CFU does not directly correlate to a clinically significant outcome, such as a defined surgical site infection requiring intervention. Nevertheless, it is noteworthy that the decrease in bacterial counts on the stainless steel screws and polyethylene washers were maintained 1 week after the Betadine lavage.
Conclusion
Dilute Betadine lavage is a simple and inexpensive adjunct for the treatment of acute postoperative arthroplasty infection and may increase the rate of component retention. Additionally, the bactericidal and antibiofilm activities of Betadine may improve the effectiveness of systemic antibiotics. Further clinical investigation is warranted.
1. Wilson MG, Kelley K, Thornhill TS. Infection as a complication of total knee-replacement arthroplasty. Risk factors and treatment in sixty-seven cases. J Bone Joint Surg Am. 1990;72(6):878-883.
2. Ridgeway S, Wilson J, Charlet A, Kafatos G, Pearson A, Coello R. Infection of the surgical site after arthroplasty of the hip. J Bone Joint Surg Br. 2005;87(6):844-850.
3. Mahomed NN, Barrett JA, Katz JN, et al. Rates and outcomes of primary and revision total hip replacement in the United States medicare population. J Bone Joint Surg Am. 2003;85(1):27-32.
4. Mahomed NN, Barrett J, Katz JN, Baron JA, Wright J, Losina E. Epidemiology of total knee replacement in the United States Medicare population. J Bone Joint Surg Am. 2005;87(6):1222-1228.
5. Parvizi J, Zmistowski B, Adeli B. Periprosthetic joint infection: treatment options. Orthopedics. 2010;33(9):659.
6. Poultsides LA, Liaropoulos LL, Malizos KN. The socioeconomic impact of musculoskeletal infections. J Bone Joint Surg Am. 2010;92(11):e13.
7. Chundamala J, Wright JG. The efficacy and risks of using povidone-iodine irrigation to prevent surgical site infection: an evidence-based review. Can J Surg. 2007;50(6):473-481.
8. Brown NM, Cipriano CA, Moric M, Sporer SM, Della Valle CJ. Dilute betadine lavage before closure for the prevention of acute postoperative deep periprosthetic joint infection. J Arthroplasty. 2012;27(1):27-30.
9. Kaysinger KK, Nicholson NC, Ramp WK, Kellam JF. Toxic effects of wound irrigation solutions on cultured tibiae and osteoblasts. J Orthop Trauma. 1995;9(4):303-311.
10. Haley CE, Marling-Cason M, Smith JW, Luby JP, Mackowiak PA. Bactericidal activity of antiseptics against methicillin-resistant Staphylococcus aureus. J Clin Microbiol. 1985;21(6):991-992.
11. Lacey RW, Catto A. Action of povidone-iodine against methicillin-sensitive and -resistant cultures of Staphylococcus aureus. Postgrad Med J. 1993;69(3 suppl):S78-S83.
12. McLure AR, Gordon J. In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus aureus. J Hosp Infect. 1992;21(4):291-299.
13. Suzuki J, Komatsuzawa H, Kozai K, Nagasaka N. In vitro susceptibility of Staphylococcus aureus including MRSA to four disinfectants. ASDC J Dent Child. 1997;64(4):260-263.
14. Yasuda T, Yoshimura S, Katsuno Y, et al. Comparison of bactericidal activities of various disinfectants against methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. Postgrad Med J. 1993;69(3 suppl):S66-S69.
15. Craig MR, Poelstra KA, Sherrell JC, Kwon MS, Belzile EL, Brown TE. A novel total knee arthroplasty infection model in rabbits. J Orthop Res. 2005;23(5):1100-1104.
16. Hartman MB, Fehring TK, Jordan L, Norton HJ. Periprosthetic knee sepsis. The role of irrigation and debridement. Clin Orthop. 1991;273:113-118.
17. Mont MA, Waldman B, Banerjee C, Pacheco IH, Hungerford DS. Multiple irrigation, debridement, and retention of components in infected total knee arthroplasty. J Arthroplasty. 1997;12(4):426-433.
18. Azzam KA, Seeley M, Ghanem E, Austin MS, Purtill JJ, Parvizi J. Irrigation and debridement in the management of prosthetic joint infection: traditional indications revisited. J Arthroplasty. 2010;25(7):1022-1027.
19. Stall AC, Becker E, Ludwig SC, Gelb D, Poelstra KA. Reduction of postoperative spinal implant infection using gentamicin microspheres. Spine (Phila Pa 1976). 2009;34(5):479-483.
20. Hota B, Ellenbogen C, Hayden MK, Aroutcheva A, Rice TW, Weinstein RA. Community-associated methicillin-resistant Staphylococcus aureus skin and soft tissue infections at a public hospital: do public housing and incarceration amplify transmission? Arch Intern Med. 2007;167(10):1026-1033.
21. Fridkin SK, Hageman JC, Morrison M, et al, Active Bacterial Core Surveillance Program of the Emerging Infections Program Network. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med. 2005;352(14):1436-1444.
22. Hosman AH, van der Mei HC, Bulstra SK, Busscher HJ, Neut D. Metal-on-metal bearings in total hip arthroplasties: influence of cobalt and chromium ions on bacterial growth and biofilm formation. J Biomed Mater Res A. 2009;88(3):711-716.
23. Oduwole KO, Glynn AA, Molony DC, et al. Anti-biofilm activity of sub-inhibitory povidone-iodine concentrations against Staphylococcus epidermidis and Staphylococcus aureus. J Orthop Res. 2010;28(9):1252-1256.
24. Cheng MT, Chang MC, Wang ST, Yu WK, Liu CL, Chen TH. Efficacy of dilute betadine solution irrigation in the prevention of postoperative infection of spinal surgery. Spine (Phila Pa 1976). 2005;30(15):1689-1693.
25. Anderson RL, Vess RW, Panlilio AL, Favero MS. Prolonged survival of Pseudomonas cepacia in commercially manufactured povidone-iodine. Appl Environ Microbiol. 1990;56(11):3598-3600.
26. Panlilio AL, Beck-Sague CM, Siegel JD, et al. Infections and pseudoinfections due to povidone-iodine solution contaminated with Pseudomonas cepacia. Clin Infect Dis. 1992;14(5):1078-1083.
1. Wilson MG, Kelley K, Thornhill TS. Infection as a complication of total knee-replacement arthroplasty. Risk factors and treatment in sixty-seven cases. J Bone Joint Surg Am. 1990;72(6):878-883.
2. Ridgeway S, Wilson J, Charlet A, Kafatos G, Pearson A, Coello R. Infection of the surgical site after arthroplasty of the hip. J Bone Joint Surg Br. 2005;87(6):844-850.
3. Mahomed NN, Barrett JA, Katz JN, et al. Rates and outcomes of primary and revision total hip replacement in the United States medicare population. J Bone Joint Surg Am. 2003;85(1):27-32.
4. Mahomed NN, Barrett J, Katz JN, Baron JA, Wright J, Losina E. Epidemiology of total knee replacement in the United States Medicare population. J Bone Joint Surg Am. 2005;87(6):1222-1228.
5. Parvizi J, Zmistowski B, Adeli B. Periprosthetic joint infection: treatment options. Orthopedics. 2010;33(9):659.
6. Poultsides LA, Liaropoulos LL, Malizos KN. The socioeconomic impact of musculoskeletal infections. J Bone Joint Surg Am. 2010;92(11):e13.
7. Chundamala J, Wright JG. The efficacy and risks of using povidone-iodine irrigation to prevent surgical site infection: an evidence-based review. Can J Surg. 2007;50(6):473-481.
8. Brown NM, Cipriano CA, Moric M, Sporer SM, Della Valle CJ. Dilute betadine lavage before closure for the prevention of acute postoperative deep periprosthetic joint infection. J Arthroplasty. 2012;27(1):27-30.
9. Kaysinger KK, Nicholson NC, Ramp WK, Kellam JF. Toxic effects of wound irrigation solutions on cultured tibiae and osteoblasts. J Orthop Trauma. 1995;9(4):303-311.
10. Haley CE, Marling-Cason M, Smith JW, Luby JP, Mackowiak PA. Bactericidal activity of antiseptics against methicillin-resistant Staphylococcus aureus. J Clin Microbiol. 1985;21(6):991-992.
11. Lacey RW, Catto A. Action of povidone-iodine against methicillin-sensitive and -resistant cultures of Staphylococcus aureus. Postgrad Med J. 1993;69(3 suppl):S78-S83.
12. McLure AR, Gordon J. In-vitro evaluation of povidone-iodine and chlorhexidine against methicillin-resistant Staphylococcus aureus. J Hosp Infect. 1992;21(4):291-299.
13. Suzuki J, Komatsuzawa H, Kozai K, Nagasaka N. In vitro susceptibility of Staphylococcus aureus including MRSA to four disinfectants. ASDC J Dent Child. 1997;64(4):260-263.
14. Yasuda T, Yoshimura S, Katsuno Y, et al. Comparison of bactericidal activities of various disinfectants against methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. Postgrad Med J. 1993;69(3 suppl):S66-S69.
15. Craig MR, Poelstra KA, Sherrell JC, Kwon MS, Belzile EL, Brown TE. A novel total knee arthroplasty infection model in rabbits. J Orthop Res. 2005;23(5):1100-1104.
16. Hartman MB, Fehring TK, Jordan L, Norton HJ. Periprosthetic knee sepsis. The role of irrigation and debridement. Clin Orthop. 1991;273:113-118.
17. Mont MA, Waldman B, Banerjee C, Pacheco IH, Hungerford DS. Multiple irrigation, debridement, and retention of components in infected total knee arthroplasty. J Arthroplasty. 1997;12(4):426-433.
18. Azzam KA, Seeley M, Ghanem E, Austin MS, Purtill JJ, Parvizi J. Irrigation and debridement in the management of prosthetic joint infection: traditional indications revisited. J Arthroplasty. 2010;25(7):1022-1027.
19. Stall AC, Becker E, Ludwig SC, Gelb D, Poelstra KA. Reduction of postoperative spinal implant infection using gentamicin microspheres. Spine (Phila Pa 1976). 2009;34(5):479-483.
20. Hota B, Ellenbogen C, Hayden MK, Aroutcheva A, Rice TW, Weinstein RA. Community-associated methicillin-resistant Staphylococcus aureus skin and soft tissue infections at a public hospital: do public housing and incarceration amplify transmission? Arch Intern Med. 2007;167(10):1026-1033.
21. Fridkin SK, Hageman JC, Morrison M, et al, Active Bacterial Core Surveillance Program of the Emerging Infections Program Network. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med. 2005;352(14):1436-1444.
22. Hosman AH, van der Mei HC, Bulstra SK, Busscher HJ, Neut D. Metal-on-metal bearings in total hip arthroplasties: influence of cobalt and chromium ions on bacterial growth and biofilm formation. J Biomed Mater Res A. 2009;88(3):711-716.
23. Oduwole KO, Glynn AA, Molony DC, et al. Anti-biofilm activity of sub-inhibitory povidone-iodine concentrations against Staphylococcus epidermidis and Staphylococcus aureus. J Orthop Res. 2010;28(9):1252-1256.
24. Cheng MT, Chang MC, Wang ST, Yu WK, Liu CL, Chen TH. Efficacy of dilute betadine solution irrigation in the prevention of postoperative infection of spinal surgery. Spine (Phila Pa 1976). 2005;30(15):1689-1693.
25. Anderson RL, Vess RW, Panlilio AL, Favero MS. Prolonged survival of Pseudomonas cepacia in commercially manufactured povidone-iodine. Appl Environ Microbiol. 1990;56(11):3598-3600.
26. Panlilio AL, Beck-Sague CM, Siegel JD, et al. Infections and pseudoinfections due to povidone-iodine solution contaminated with Pseudomonas cepacia. Clin Infect Dis. 1992;14(5):1078-1083.
