Extensor mechanism allograft reconstruction after total knee arthroplasty.
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 the use of an extensor mechanism allograft in revision total knee arthroplasty.


METHODS
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.


RESULTS
All of the reconstructions in Group I were clinical failures, with an average postoperative extensor lag of 59 degrees (range, 40 degrees to 80 degrees ) 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 degrees (range, 0 degrees to 15 degrees ) (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 degrees ) and Group II (average, 104 degrees ) (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.
Burnett
R Stephen J
RS
Department of Orthopaedic Surgery, Barnes Jewish Hospital, Washington University, 660 South Euclid Avenue, Campus Box 8233, St. Louis, MO 63110, USA. burnetts@msnotes.wustl.edu
Berger
Richard A
RA
Della Valle
Craig J
CJ
Sporer
Scott M
SM
Jacobs
Joshua J
JJ
Paprosky
Wayne G
WG
Rosenberg
Aaron G
AG
D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001696:Biomechanical Phenomena; D006801:Humans; D007719:Knee Joint; D019637:Orthopedic Procedures / Q000379:methods*; D016059:Range of Motion, Articular; D019651:Plastic Surgery Procedures / Q000379:methods; D020127:Recovery of Function; D013708:Tendon Injuries / Q000209:etiology / Q000601:surgery*; D013710:Tendons / Q000637:transplantation*; D014184:Transplantation, Homologous