The Effect of Mechanical Leg Alignment on Cartilage Restoration With and Without Concomitant High Tibial Osteotomy.

PURPOSE: To assess graft survivorship in patients who underwent autologous chondrocyte implantation (ACI) or osteochondral allograft transplantation (OCA) for the treatment of focal full-thickness cartilage lesions on the medial femoral condyle with and without concomitant high tibial osteotomy (HTO), depending on the preoperative lower-extremity alignment. A secondary purpose was to retrospectively evaluate associated factors for ACI and OCA graft failures. METHODS: A total of 168 patients who underwent cartilage repair with ACI or OCA with or without HTO for focal chondral defects on the medial femoral condyle by a single surgeon between March 2007 and February 2018 were included. Clinical notes, operative reports, and radiographic imaging were reviewed for each patient. Detailed Kaplan-Meier analyses were performed based on patient's mechanical axis alignment. In a subanalysis, failures and nonfailures in patients treated with ACI or OCA were comparatively evaluated. RESULTS: In ACI, neutral mechanical alignment resulted in a significantly longer graft survival compared with slight valgus alignment (P = .003 and P = .05, respectively). No significant differences in survivorship were seen based on mechanical axis alignment in OCA patients (P > .05). Patients who were considered failures after ACI presented significantly more often with valgus alignment (P = .002), whereas failures in the OCA group were more often female and smokers (P = .025; P = .034). CONCLUSIONS: In summary, the results of this study suggest that neutral mechanical axis alignment, regardless if physiologic or through HTO, improves survivorship in patients undergoing medial compartment ACI. Neutral alignment also showed a trend towards improved survivorship in patients after OCA, but this did not reach statistical significance. LEVEL OF EVIDENCE: Case-Series; Level of evidence, 4.