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Extensor mechanism failure following total knee arthroplasty

Extensor mechanism failure following total knee arthroplasty is a rare but potentially devastating complication with an overall incidence of 0.17%–2.5%. The 3 main causes of disruption include quadriceps tendon rupture, patellar fracture, or patellar tendon rupture. Clinical presentation can vary from asymptomatic to the acutely painful and swollen knee, but for most patients, there will be evidence of extensor lag and/or difficulty performing straight leg raise. A variety of treatment options have been described in the literature to date including nonoperative management with immobilization, particularly for patients with an extensor lag of <20°. Direct repair may be useful in the management of acute tendon ruptures; however, augmentation is now also recommended in addition. Options for augmentation include tendon autografts or synthetic materials. The use of allografts such as Achilles tendon allografts or complete extensor mechanism allografts and rotational flaps has also been described. Treatment of patellar fractures varies depending on fracture pattern, degree of extensor lag, presence of patellar component loosening, and patellar bone stock. The potential options for treatment include nonoperative management with immobilization, open reduction and internal fixation, patellectomy (either partial or complete), or revision surgery, although this list is not exhaustive. Outcomes are poor with complications including rerupture, postoperative infection, nonunion, or residual extensor lag with associated poor functional outcomes and high reoperation rates. There is a distinct lack of high-quality evidence in the literature at present, and as such, further research is required to make any recommendations for treatment.