The role of autologous bone grafting in matrix‐associated autologous chondrocyte implantation at the knee: Results from the German Cartilage Registry (KnorpelRegister DGOU)

Abstract Purpose To investigate whether concomitant autologous bone grafting adversely affects clinical outcome and graft survival after matrix‐associated autologous chondrocyte implantation (M‐ACI). Methods The present study examines registry data of patients who underwent M‐ACI with or without autologous bone grafting for large‐sized chondral or osteochondral defects. Propensity score matching was performed to exclude potential confounders. A total of 215 patients with similar baseline characteristics were identified. Clinical outcome was assessed at the time of surgery and at 6, 12, 24, 36 and 60 months using the Knee Injury and Osteoarthritis Outcome Score (KOOS). KOOS change, clinical response rate, KOOS subcomponents and failure rate were determined. Results Patients treated with M‐ACI and autologous bone grafting achieved comparable clinical outcomes compared with M‐ACI alone. At 24 months postoperatively, the patient‐reported outcome (PRO) of patients treated with M‐ACI and autologous bone grafting was even significantly better as measured by KOOS (74.9 ± 18.8 vs. 79.2 ± 15.4; p = 0.043). However, the difference did not exceed the minimal clinically important difference (MCID). In patients with M‐ACI and autologous bone grafting, a greater change in KOOS relative to baseline was observed at 6 (9.3 ± 14.7 vs. 15.0 ± 14.7; p = 0.004) and 12 months (12.6 ± 17.2 vs. 17.7 ± 14.6; p = 0.035). Overall, a high clinical response rate was observed in both groups at 24 months (75.8% vs. 82.0%; p = n.s.). The estimated survival at the endpoint of reoperation for any reason was 82.1% (SD 2.8) at 8.4 years for isolated M‐ACI and 88.7% (SD 2.4) at 8.2 years for M‐ACI with autologous bone grafting ( p = 0.039). Conclusions Even in the challenging cohort of large osteochondral defects, the additional treatment with autologous bone grafting leads to remarkably good clinical outcomes in patients treated with M‐ACI. In fact, they tend to benefit more from surgery, have lower revision rates and achieve clinical response rates earlier. Subchondral bone management is critical to the success of M‐ACI and should be addressed in the treatment of borderline defects. Level of Evidence Level III.