Paper 53. Impact of Osteoarthritis on Outcomes After Implantation of an Aragonite-Based Scaffold for Knee Chondral and Osteochondral Defects: Analysis of an RCT at 5-Year Follow-up

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Objectives: An aragonite-based, biphasic, acellular scaffold (ABS) has been developed for the treatment knee cartilage lesions. Previously published results from an RCT comparing ABS to surgical standard of care (SSOC, i.e., debridement/microfracture) showed superior clinical outcomes at 24 months post-operatively. The purpose of this covariate analysis was to compare primary and secondary outcomes between treatment groups among patients with no-to-minimal OA (Kellgren-Lawrence Grade 0-1) and mild-to-moderate OA (Kellgren-Lawerence Grade 2-3) at 60-months post-operative. Our hypothesis was that there would be no difference in primary and secondary outcomes between arthritic and non-arthritic patient cohorts treated with ABS. Methods: 251 patients aged 21-75 years with <=3 ICRS grade 3a lesions on the femoral condyles and/or trochlea and without severe osteoarthritis (K/L grade 4) were randomized to ABS (n=167) or SSOC (n=84). Primary endpoint was the change from baseline to 60 months in KOOS Overall Score. Secondary confirmatory endpoints included change from baseline to 60 months in KOOS subscales (Pain, Symptoms, QOL, ADL, and Sports) and KOOS responder rate (>=30-point increase from baseline). Baseline observation carried forward imputation was applied for treatment failures. A covariate analysis was conducted on patients in the implant and SSOC groups with no-to-minimal OA (90 and 53 patients, respectively) and mild-to-moderate OA (74 and 30 patients, respectively). The primary and secondary confirmatory endpoints were analyzed for this covariate in a mixed model for repeated measures (MMRM). An interaction P < .15 was considered evidence supporting the presence of heterogeneity of treatment effects. Results: The implant group had superior mean overall KOOS scores to the SSOC group at each timepoint. The mean change from baseline to 60 months in the overall KOOS score and the KOOS subscale scores was twice as large for the implant group as the SSOC group (all p<.005). The mean change in the overall KOOS score from baseline to 60 months for those with no-to-minimal OA was 39.4 points in the implant group and 14.3 points in the SSOC group. Among those with mild-to-moderate OA, the mean change was 39.8 in the implant group and 18.2 in the SSOC group. The Bayesian posterior probability of superiority for changes in overall KOOS from baseline to 60 months was >0.999 in favor of the implant group vs. the SSOC group among patients with mild-to-moderate OA and those with no-to-minimal OA. Based on the MMRM, the treatment group difference at 60 months was 20.7 (95% CI, 11.2-30.2; P < .001) for no-to-minimal OA and 17.2 (95% CI, 8.6-25.9 P < .001) for mild-to-moderate OA. There was no evidence that superiority margin was based on degree of OA (P = 0.842).Among patients with no-to-minimal OA, the overall KOOS responder rate at 60 months was 74.7% (59/79 patients) in the implant group compared with 16.7% (4/24 patients) in the SSOC group. Among patients with mild-to-moderate OA, the overall KOOS responder rate at 60 months was 74.6% (50/67 patients) in the implant group compared with 36.2% (17/47 patients) in the SSOC group. Among patients in the implant group, those with no-to-minimal OA and those with mild-to-moderate OA, improvements in mean KOOS overall score from baseline to 60 months were similar (39.4 and 39.8, respectively). Similar patterns were seen for the KOOS subscale scores. Conclusions: Patients in the aragonite-based scaffold group with no-to-minimal OA and those with mild-to-moderate OA had significantly superior outcomes compared to their counterparts treated with SSOC. Further, patients in the scaffold group with mild-to-moderate OA had similar outcomes to patients in the scaffold group with no-to-minimal OA. These results suggest the aragonite-based scaffold offers an effective treatment option for patients with knee chondral and osteochondral lesions with or without OA.

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