The Journal of Bone and Joint Surgery (American). 2004;86:2694-2699
© 2004 The Journal of Bone and Joint Surgery, Inc.
Extensor Mechanism Allograft Reconstruction After Total Knee Arthroplasty
A COMPARISON OF TWO TECHNIQUES
R. Stephen J. Burnett, MD, FRCS(C)1,
Richard A. Berger, MD2,
Wayne G. Paprosky, MD2,
Craig J. Della Valle, MD2,
Joshua J. Jacobs, MD2 and
Aaron G. Rosenberg, MD2
1 Washington University School of Medicine, 660 South Euclid Avenue, Campus Box
8233, St. Louis, MO 63110
2 Department of Orthopedic Surgery, Rush University Medical Center, 1725 West
Harrison Street, Suite 1063, Chicago, IL 60612
Investigation performed at the Department of Orthopedic Surgery, Rush
University Medical Center, Chicago, Illinois
The authors did not receive grants or outside funding in support of their
research or preparation of this manuscript. They did not receive payments or
other benefits or a commitment or agreement to provide such benefits from a
commercial entity. 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 nonprofit organization with which the
authors are affiliated or associated.
Background: 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 use of an
extensor mechanism allograft following total knee arthroplasty.
Methods: Twenty consecutive reconstructions with 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.
Results: 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).
Conclusions: 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.
Level of Evidence: Therapeutic study, Level III-2
(retrospective cohort study). See Instructions to Authors for a complete
description of levels of evidence.

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