The Effect of Mechanical Leg Alignment on Cartilage Restoration with and without Concomitant High Tibial Osteotomy.

Purpose To assess graft survivorship in patients that underwent autologous chondrocyte implantation (ACI) or osteochondral allograft transplantation (OCA) for the treatment of focal full-thickness cartilage lesions on the medial femoral condyle (MFC) with and without concomitant high tibial osteotomy (HTO), depending on the pre-operative 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 MFC 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 sub-analysis, failures and non-failures in patients treated with ACI or OCA were comparatively evaluated. Results In ACI, neutral mechanical alignment resulted in a significantly longer graft survival compared to slight valgus alignment (p = 0.003 and p = 0.05, respectively). No significant differences in survivorship were seen based on mechanical axis alignment in OCA patients (p > 0.05). Patients that were considered failures after ACI presented significantly more often with valgus alignment (p = 0.002), whereas failures in the OCA group were more often female and smokers (p = 0.025; p = 0.034). Conclusion 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.