Far more common but still rare, fracture-type complications involve the extensor mechanism and the tibial plateau. Patellar fractures have been documented as occurring in 0.2% to 2.3% of cases.5-7 One paper reported a fracture in 1.3% of cases at a mean of 57 days, with roughly half caused by trauma and the other half having atraumatic causes.8 Lee and colleagues9 found a 0.2% complication rate for all BPTB grafts in 1725 consecutive patients. Although some patients were treated nonoperatively, others underwent operative fixation. Time to clinical and radiographic healing was 7 and 10 weeks, respectively.
Tibial plateau fracture after BPTB harvest is a rare complication, with 11 cases reported in the literature.10 In 4 of those cases, the proposed mechanism of fracture was a stress riser resulting from the synergistic weakness of the tibial harvest site combined with the tibial tunnel reducing proximal tibial bone strength.11-14 The mechanism of injury varied from traumatic to insufficiency fracture, with fixation varying with fracture displacement.
Tibial tubercle fracture after BPTB harvest is extremely rare, with the present case being only the third published in the literature. Like most reported post-ACL reconstruction extensor mechanism disruptions, our case resulted from a traumatic event at an interval after surgery. All other tibial tubercle fracture post-ACL reconstruction disruptions occurred within 2 weeks after surgery.1,2 Sudden tension on the extensor mechanism secondary to hyperflexion caused a fracture through a weakened tibial tubercle with avulsion of the remaining tendon in 2 of the 3 cases, with the third being a lower stress popping noise that occurred during a pivot to stand.1
The residual defect after tibial bone block harvest could represent a weakening of the tubercle by loss of structural bone and by development of stress risers. The previous reports of tibial tubercle fracture after BPTB harvest documented a similar methodology: Use a bone saw and osteotomes to harvest a trapezoidal tibial bone plug 10 mm to 11 mm wide and 22 cm to 35 cm long. As previously documented, we suggest taking care with saw cuts and osteotomes so as not to weaken the proximal tibia or distal patella more than is necessary.1,2 Before surgery, patients should be warned about the possibility of extensor mechanism injuries with use of BPTB grafts.
Conclusion
Tibial tubercle fracture after BPTB harvest for ACL reconstruction is an extremely rare complication. Treatment is ORIF of the tubercle fragment, with a delay in ACL rehabilitation in cases involving the ipsilateral knee.
Am J Orthop. 2016;45(7):E469-E471. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.