Summary

Extensor mechanism allograft after total knee arthroplasty was a reasonable and reliable surgical option, although considered a "last resort" procedure.

Abstract

Objectives
Extensor mechanism rupture is a feared complication after total knee arthroplasty (TKA). The current trend for chronic ruptures is extensor mechanism allografts (EMA). This study aimed to evaluate EMA's survival and functional outcomes after TKA.

Methods

This retrospective, single-centre study included all patients who underwent an EMA on TKA between 2011 and 2022, with a minimum follow-up of 12 months. Exclusion criteria were allografts on native knees and partial EMA. Fifty EMA were included (50 patients). The mean age was 65.8±9 years. Most extensor mechanism ruptures were located on the patellar tendon (36.0%) and the quadricipital tendon (34.0%). Twenty-one patients underwent EMA at the same time as TKA revision (42%). Twenty-nine patients underwent isolated EMA without TKA revision (58%). The analysis focused on the rate of mechanical and septic complications, survival without revision of the allograft, and functional outcomes.

Results

The mean knee extension deficit was 17.8° (±29.5°) after a mean follow-up of 20.4 months (12-53). The complication rate was 30% (n=15), including 6% of septic complications (n=3) and 24% of mechanical complications (n=12). The most common cause of mechanical failure was quadricipital tendon rupture (n=7). The allograft revision-free survival rate was 81.5%, with a mean revision time of 11.3 months. Functional outcomes, mechanical complication rates, and allograft survival were not affected by concomitant TKA revision. In the preoperative quadricipital tendon rupture subgroup, there was a 29.4% re-rupture at the same level of the quadricipital tendon.

Conclusion

EMA on TKA was a reasonable and reliable surgical option, although considered a "last resort" procedure. This procedure was associated with significant morbidity and modest functional outcomes but with a satisfactory mid-term allograft survival rate. The quadricipital tendon was a particular area of vulnerability for these allografts. Concomitant revision of the TKA did not increase complications or compromise allograft survival.