Partial extensor mechanism allograft reconstruction for chronic patellar tendon disruption shows superior outcomes in native knees when compared to same technique following total arthroplasty.

PURPOSE: Chronic patellar tendon disruption occurs mostly after total knee arthroplasty, and is a challenging complication to treat. We have previously described an original technique for reconstruction using extensor mechanism allograft. The goal of this study was to assess the results of this technique in TKA and native knees.

METHODS: An observational, single centre, retrospective study was conducted. Nine patients in the TKA group and eight in the native knee group were included, all treated for chronic PT rupture. The operative technique included fresh-frozen allograft, in which the patella was fashioned into an hourglass shape and press-fit in a corresponding groove in the native patella. The primary outcome was failure of the graft defined by a residual extensor lag > 10°.

RESULTS: The mean age was 68 in the TKA group and 51 in the native group. The minimum follow-up was 24 months and the mean follow-up respectively 42 and 39 months. 33% of allografts failed in the TKA group where none failed in the native knee group, with a mean extension lag of 12.2° (0-30) and 1.25° (0-5), respectively. All but the three failures presented with an extension lag < 10°. Four cases of patellar bone block distal migration, less than 1 cm, were recorded in the native knee group without clinical repercussion.

CONCLUSIONS: The results of this original technique in the setting of chronic PT rupture were excellent for native knees at a minimum follow-up of 24 months. However, results were less satisfactory in the TKA group, due to the substantial rate of failure. LEVEL OF EVIDENCE III.