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Extensor mechanism insufficiency is a rare but unfortunate event in revision total knee arthroplasty (TKA). This video describes two techniques for extensor mechanism reconstruction during revision TKA: reconstruction with the use of an entire extensor mechanism allograft and reconstruction via the mesh technique described by Hanssen.

Entire extensor mechanism allograft reconstruction: Typically, a standard revision TKA approach is used. The previous patella is removed. The proximal tibia is prepared, and three stainless-steel 18-gauge wires are passed into six holes. These wires will be used to fix the allograft on the tibial side and stabilized during cementation of the tibial component. The host tibial tubercle is prepared with the use of a microsagittal row and removed, and the allograft tibial tubercle is press-fit into this hole. The allograft is tensioned in full extension, and the quadriceps junction is repaired with the use of locking Krackow stitches. The host quadriceps is sutured over the top of the allograft, covering as much of the allograft as possible. Postoperatively, the knee is immobilized in full extension in a cast for 6 to 8 weeks. Gradual range of motion recovery with the use of a hinged knee brace is begun 8 weeks postoperatively. Few studies, with small numbers and short follow-up, are available on the outcomes of extensor mechanism allograft reconstruction. Most studies agree that better results are obtained if the allograft is tensioned in full extension. Contraindications to this technique are insufficient tibial bone, infection, and lack of compliance with cast immobilization.

Synthetic mesh reconstruction: Typically, a standard revision TKA approach is used. The synthetic mesh is a knitted, monofilament, polypropylene, heavy-weight mesh commonly used for hernia and urologic procedures. A single 25- x 35.5-cm sheet of mesh is tabularized into a 2- to 2.5-cm wide graft and secured with the use of multiple heavy nonabsorbable sutures. The tibial side is prepared to receive the synthetic mesh, and a trough is created in the anteromedial tibial cortex. The mesh is inserted in the tibia through this hole and fixed using the tibial component. A portal is created in the lateral soft tissues to allow for delivery of the graft from deep to superficial. The mesh is then secured proximally to the quadriceps tendon and to the vastus lateralis with the use of multiple nonabsorbable sutures. The vastus medialis and retinaculum are mobilized to overlap the graft in a pants-over-vest fashion. The reconstruction is tensioned in full extension. Postoperatively, the knee is immobilized in full extension in a resin cast for 6 to 8 weeks, with toe-touch weight bearing allowed. After resin cast removal, progressive full weight bearing is allowed in 4 to 6 weeks, and range of motion recovery is progressively permitted. This technique is indicated in patients with a chronic patellar fracture or nonunion, patients who have undergone patellectomy, and patients in whom reconstruction with the use of allograft has failed. Contraindications to this technique are active infection, inadequate skin coverage, and severe medical comorbidities.

Extensor mechanism rupture is a serious event associated with a high rate of complications and failure. Reconstruction with the use of an entire allograft or synthetic mesh are viable treatment options. Good tension of the graft is mandatory to achieve good results and a low rate of extensor lag.