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Using a Modified Ball-Tip Guide Rod to Equalize Leg Length and Restore Femoral Offset

Am J Orthop. 2017 January;46(1):E10-E12

References

1. Whitehouse MR, Stefanovich-Lawbuary NS, Brunton LR, Blom AW. The impact of leg length discrepancy on patient satisfaction and functional outcome following total hip arthroplasty. J Arthroplasty. 2013;28(8):1408-1414.

2. Clark CR, Huddleston HD, Schoch EP 3rd, Thomas BJ. Leg-length discrepancy after total hip arthroplasty. J Am Acad Orthop Surg. 2006;14(1):38-45.

3. O’Brien S, Kernohan G, Fitzpatrick C, Hill J, Beverland D. Perception of imposed leg length inequality in normal subjects. Hip Int. 2010;20(4):505-511.

4. Hofmann AA, Skrzynski MC. Leg-length inequality and nerve palsy in total hip arthroplasty: a lawyer awaits! Orthopedics. 2000;23(9):943-944.

5. Knutson GA. Anatomic and functional leg-length inequality: a review and recommendation for clinical decision-making. Part I, anatomic leg-length inequality: prevalence, magnitude, effects and clinical significance. Chiropr Osteopat. 2005;13:11.

6. Iagulli ND, Mallory TH, Berend KR, et al. A simple and accurate method for determining leg length in primary total hip arthroplasty. Am J Orthop. 2006;35(10):455-457.

7. Ranawat CS, Rao RR, Rodriguez JA, Bhende HS. Correction of limb-length inequality during total hip arthroplasty. J Arthroplasty. 2001;16(6):715-720.

8. Weber M, Woerner M, Springorum R, et al. Fluoroscopy and imageless navigation enable an equivalent reconstruction of leg length and global and femoral offset in THA. Clin Orthop Relat Res. 2014;472(10):3150-3158.

9. Alazzawi S, Douglas SL, Haddad FS. A novel intra-operative technique to achieve accurate leg length and femoral offset during total hip replacement. Ann R Coll Surg Engl. 2012;94(4):281-282.

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Discussion

Various techniques of assessing intraoperative leg length have been described, and each has its advantages and disadvantages. Relying on abductor tension or comparing leg lengths on the operating table is not always accurate and is strongly dependent on patient position.^2,6

Referencing the tip of the greater trochanter to a Steinmann pin inserted into the ilium provides a precise reference point, but this invasive technique has the potential for fracture propagation through the drill hole.^2,7Superimposing a trial femoral component over the proximal femur to determine the appropriate femoral neck osteotomy has been described, but this process can be difficult through a tight DA approach.⁹Numerous measuring devices have been designed to help restore leg length, but in many cases the purchase cost and required maintenance outweigh their utility.² Gililland and colleagues¹⁰ developed a reusable fluoroscopic transparent grid system that significantly improves component positioning during DA-THA.

The modified ball-tip guide rod is relatively inexpensive (<$100) and has several practical purposes in total joint surgery. The guide rod historically has been used to sound the center of the femoral canal before broaching. In revision cases and in cases of poor bone stock, the tool can be used to verify that cortical perforation has not occurred during canal preparation. In this article, we describe another realistic use for the guide rod: to create, during DA-THA, a radiographic reference line that can be used to help restore leg length and femoral offset.

Several authors have mentioned surgeons’ drawing the reference line on paper printouts of intraoperative images.¹¹ Not only is this practice fraught with potential contamination of the operative field, but valuable time is lost waiting for paper copies and putting on a new gown and gloves before reentering the sterile field.

We used to train a radiologic technician or operating room nurse to draw a computerized reference line connecting the lesser trochanters on the fluoroscopic image. Problems arose in working with revolving nursing staff and in distinguishing the thin black line on computer monitors. In contrast, the radiopaque line from the guide rod is easily differentiated on fluoroscopic images, the technique poses less of a risk to the sterile field, and proper orientation of the guide rod to obtain the appropriate reference line is entirely surgeon-dependent.

A drawback of this technique is the additional radiation exposure that occurs when extra images are obtained to ensure satisfactory alignment of the guide rod. Another issue is fluoroscopic parallax. Some machines in the operating department generate a magnetic field that can interfere with the fluoroscopy beam and thereby slightly distort the intraoperative images.⁸ Therefore, it is imperative that the guide rod remain perfectly straight to avoid confounding measurements.

Our modified guide rod technique is a reliable, quick, and inexpensive intraoperative tool that helps in accurately restoring leg length and femoral offset during DA-THA.

Using a Modified Ball-Tip Guide Rod to Equalize Leg Length and Restore Femoral Offset

References

Discussion

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