Essential Surgical Techniques
Extensor Mechanism Allograft Reconstruction After Total Knee Arthroplasty
R. Stephen J. Burnett, MD, FRCS(C); Richard A. Berger, MD; Craig J. Della Valle, MD; Scott M. Sporer, MD; Joshua J. Jacobs, MD; Wayne G. Paprosky, MD; Aaron G. Rosenberg, MD



Disruption of the extensor mechanism is an uncommon but catastrophic complication of total knee arthroplasty. We evaluated two techniques of reconstructing a disrupted extensor mechanism with the use of an extensor mechanism allograft in revision total knee arthroplasty.


Twenty consecutive reconstructions with the use of an extensor mechanism allograft consisting of the tibial tubercle, patellar tendon, patella, and quadriceps tendon were performed. The first seven reconstructions (Group I) were done with the allograft minimally tensioned. The thirteen subsequent procedures (Group II) were performed with the allograft tightly tensioned in full extension. All surviving allografts were evaluated clinically and radiographically after a minimum duration of follow-up of twenty-four months.


All of the reconstructions in Group I were clinical failures, with an average postoperative extensor lag of 59° (range, 40° to 80°) and an average postoperative Hospital for Special Surgery knee score of 52 points. All thirteen reconstructions in Group II were clinical successes, with an average postoperative extensor lag of 4.3° (range, 0° to 15°) (p < 0.0001) and an average Hospital for Special Surgery score of 88 points. Postoperative flexion did not differ significantly between Group I (average, 108°) and Group II (average, 104°) (p = 0.549).


The results of reconstruction with an extensor mechanism allograft after total knee arthroplasty depend on the initial tensioning of the allograft. Loosely tensioned allografts result in a persistent extension lag and clinical failure. Allografts that are tightly tensioned in full extension can restore active knee extension and result in clinical success. On the basis of the number of knees that we studied, there was no significant loss of flexion. Use of an extensor mechanism graft for the treatment of a failure of the extensor mechanism will be successful only if the graft is initially tensioned tightly in full extension.


  • In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from Zimmer. In addition, one or more of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (Zimmer). Also, a commercial entity (Zimmer) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or non-profit organization with which the authors are affiliated or associated.

  • The line drawings in this article are the work of Jennifer Fairman (jfairman{at}

  • Investigation performed at the Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois

  • The original scientific article in which the surgical technique was presented was published in JBJS Vol. 86-A, pp. 2694-2699, December 2004

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