Effect of Mechanical Alignment on Clinically Significant Outcomes, Reoperation, and Failure After Osteochondral Allograft Transplantation of the Knee

Background: Identifying and addressing mechanical malalignment is an important component of treating symptomatic osteochondral defects with osteochondral allograft (OCA) transplantation. However, little is known about how malalignment influences short- to midterm outcomes after OCA transplantation. Purpose: To evaluate whether mechanical alignment measurements including the hip-knee-ankle (HKA) angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA) predict clinically significant outcome achievement, graft failure, and reoperation after OCA transplantation with or without concomitant realignment. Study Design: Case series; Level of evidence, 4. Methods: Patient-reported outcome measures (PROMs) were collected preoperatively and at a minimum 2-year follow-up in patients receiving OCA from 2005 to 2023. PROMs included the International Knee Documentation Committee score and Knee injury and Osteoarthritis Outcome Score subscales. Clinically significant outcome thresholds were the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and Patient Acceptable Symptom State (PASS). Preoperative full-length, weightbearing radiographs were used to measure the HKA angle, LDFA, MPTA, and JLCA. Multivariable logistic regression was used for clinically significant outcome achievement and all-cause reoperation; failure and arthroplasty were summarized descriptively because of the low number of events. Results: A total of 66 patients (mean age, 34.1 ± 11.5 years; mean body mass index, 27.8 ± 4.8 kg/m 2 ; 50% female) met inclusion criteria. Mean alignment measurements were 1.8°± 4.0° for the HKA angle, 86.8°± 2.3° for the LDFA, 86.3°± 2.3° for the MPTA, and 1.7°± 1.0° for the JLCA. Although PROMs improved at the final follow-up, no preoperative alignment measure was statistically associated with MCID, PASS, or SCB achievement or with all-cause reoperation ( P > .05). In total, 25 (37.9%) patients underwent reoperation; graft survivorship was 93.9%, with 4 failures and 3 arthroplasty conversions. In an exploratory subanalysis, 16 patients with an HKA angle >5° of varus or valgus (13 with concomitant realignment) did not have significantly different rates of reoperation (43.8% vs 36.0%; P = .768) or graft failure (6.3% vs 6.0%; P > .999) compared to their remaining counterparts. Conclusion: In this small, heterogeneous cohort, preoperative mechanical alignment measures were not statistically associated with clinically significant outcome achievement or all-cause reoperation after OCA transplantation. These hypothesis-generating findings do not establish the absence of an alignment effect or define a threshold for realignment because most patients with severe preoperative malalignment underwent concomitant realignment, which may have contributed to the favorable overall outcomes, and failure events were infrequent.