Abstract
Extensor mechanism complications after or during total knee arthroplasty (TKA) are problematic. The prevalence ranges from 1%-12% in TKA patients. Treatment results for these problems are inferior to the results of similar problems in non-TKA patients. Furthermore, the treatment algorithm is fundamentally different from that of non-TKA patients. The surgeon's first question does not focus on primary fixation; rather the surgeon must ask if the patient needs surgery and if so am I prepared to augment the repair? Quadriceps tendon rupture, peri-prosthetic patellar fracture, and patellar tendon rupture have similar treatment algorithms. Patients who are able to perform a straight leg raise and have less than a 20-degree extensor lag are generally treated non-operatively with extension bracing. The remaining patients will need surgical reconstruction of the extensor mechanism. Loose patellar components are removed. Primary repair alone is associated with poor results. Whole extensor mechanism allograft, Achilles tendon allograft, and synthetic mesh reconstruction are the current techniques for augmentation. In the acute setting if these are not available, hamstring tendon harvest and augmentation is an option. Achilles tendons and synthetic mesh are easier to obtain than an entire extensor mechanism but are limited to patients that have an intact patella and the patella that can be mobilised to within 2–3 cm of the joint line. No matter which technique is used the principles are: rigid distal/tubercle fixation, coverage of allograft/mesh with host tissue to decrease infection, tensioning the augment material in extension, no flexion testing of reconstruction and post-operative extension bracing.
