Extensor mechanism reconstruction with allograft following total knee arthroplasty: a systematic review and meta-analysis of achilles tendon versus extensor mechanism allografts for isolated chronic patellar tendon ruptures.

backgroundExtensor mechanism rupture is a severe complication with an incidence of 0.1-2.5% after total knee arthroplasty (TKA). Achilles tendon allograft (ATA) and extensor mechanism allograft (EMA) in TKA surgery have yielded mixed clinical results. Our systematic review aims to identify the proportion of failure in extensor mechanism reconstruction after TKA using allograft and evaluate clinical and functional outcomes and the most common complications. Furthermore, we performed a meta-analysis among studies dealing with isolated patellar tendon ruptures to assess the failure rate, surgical complications, and clinical findings (extensor lag and knee range of motion) of extensor mechanism reconstruction using either ATA or EMA grafts.

methodsA systematic review of the literature was performed following the PRISMA guidelines, including the studies dealing with the use of EMA and ATA for extensor mechanism rupture following TKA. Coleman Methodology Score and the MINORS score were used to assess the quality of the studies. A meta-analysis was performed to evaluate the failure rate, complications, and clinical findings (extensor lag and knee range of motion) of the ATA and EMA treatments in isolated patellar tendon ruptures.

resultsA total of 238 patients (245 knees), with a mean age ranging from 54 to 74 years, who underwent extensor mechanism reconstruction with an allograft were identified in the 18 included studies. We analysed 166 patellar tendon ruptures, 29 quadriceps tendon ruptures, and 29 patellar fractures in the analysis. A chronic injury was described in the majority of included cases. ATA and whole EMA were used in 89 patients (92 knees) and 149 patients (153 knees), respectively. The overall failure percentage was 23%, while EMA and ATA were 23 and 24%. The most common complication was extensor lag (≥ 20°). The overall incidence of postoperative infection was 7%. Eleven of 14 included papers reported more than 100° of the mean postoperative knee flexion. The percentage of patients requiring walking aids is 55 and 34.5% in ATA and EMA, respectively. The failure outcome after extensor mechanism reconstruction in isolated patellar tendon ruptures was 27%, with no statistical difference between EMA and ATA in terms of failure rate and clinical outcomes.

conclusionsExtensor mechanism reconstruction with allograft represents a valid treatment option in patients with acute or chronic rupture following total knee arthroplasty. Persistent extensor lag represents the most common complication. EMA is associated with a lower frequency of patients requiring walking aids at last follow-up, although it has similar clinical and functional outcomes to ATA. In patellar tendon ruptures, ATA has a comparable success rate with EMA. LEVEL OF EVIDENCE: Level IV, therapeutic study.

trial registrationPROSPERO 2019 CRD42019141574.