Extensor Mechanism Reconstruction Using Marlex Mesh: Is Postoperative Casting Mandatory?

Abstract

Extensor mechanism (EM) disruption after total knee arthroplasty is a catastrophic complication. Reconstruction using monofilament polypropylene mesh (Marlex Mesh; CR Bard, Franklin Lakes, NJ) has emerged as the preferred treatment, but reports are limited to the designing institution. This study describes a nondesigner experience and compares 2 postoperative immobilization strategies: long leg cast vs knee immobilizer. A retrospective review of consecutive EM reconstructions between 2012 and 2019 was performed. Primary repairs and allograft reconstructions were excluded, leaving 33 knees (30 patients) who underwent Marlex reconstruction. Mean time from disruption to reconstruction was 14 months, and 14 of 33 (42%) had previous repair or reconstruction attempts. The mean age was 69 years, and mean body mass index was 35 kg/m². Postoperatively, extension was maintained using a knee immobilizer in 19 of 33 (58%) patients, whereas 14 of 33 (42%) patients were long leg casted. Kaplan-Meier analysis determined all-cause survivorship free of mesh failure. At mean 25-month follow-up, 19 of 33 (58%) EM reconstructions were functioning. Excluding explanted infections (5 recurrent and 2 new), 19 of 26 (73%) EM reconstructions were in situ. Six-year survivorship was 69% and not influenced by immobilization type (cast: 67%, immobilizer: 71%; P = .74). Extensor lag was not associated with immobilization type, improving from a mean preoperative lag of 43° to a mean postoperative lag of 9°. Among successes, University of California at Los Angeles activity and Knee Injury and Osteoarthritis Outcome Score - Joint Replacement score improvements exceeded minimal clinically important difference (2.2-3.3 and 52.5-64.0, respectively). Marlex mesh EM reconstruction is a durable and reliable treatment with acceptable clinical results achievable outside the designer institution. Provided sufficient duration and compliance with postoperative immobilization, similar outcomes can be obtained with either a cast immobilizer or a knee immobilizer.