More Durable Cartilage Repair and Better Clinical Outcomes at 5 Years Using Allogeneic Umbilical Cord Blood‐Derived Mesenchymal Stem Cells and Hyaluronate Composite Implantation Versus Microfracture for Knee Osteoarthritis

Purpose To compare the 5‐year clinical and magnetic resonance imaging (MRI) outcomes of allogeneic umbilical cord blood‐derived mesenchymal stem cells and hyaluronate (UCB‐MSCs‐HA) composite implantation versus microfracture in osteoarthritic knees and to evaluate factors associated with durable repair tissue. Methods This retrospective subset analysis of a phase 3 trial included patients with Kellgren‐Lawrence grade I to III osteoarthritis who were treated with allogeneic UCB‐MSCs‐HA implantation or microfracture and completed serial MRI and clinical evaluations up to 5 years postoperatively. Clinical outcomes included the visual analog scale, the Western Ontario and McMaster Universities Osteoarthritis Index, and International Knee Documentation Committee scores. MRI outcomes were assessed using the Magnetic Resonance Observation of Cartilage Repair Tissue score at 3 and 5 years. Durable repair was defined as Magnetic Resonance Observation of Cartilage Repair Tissue >60 at both evaluations with <10‐point interval change. Results Of the 89 patients in the original trial, 64 were included, and 48 completed the 5‐year follow‐up. At 5 years, UCB‐MSCs‐HA showed better visual analog scale (23.4 [0‐69] vs 46.3 [7‐90]; P = .0019), Western Ontario and McMaster Universities Osteoarthritis Index (21.8 [0‐70] vs 37.7 [3‐79]; P = .016), and International Knee Documentation Committee scores (59.4 [20.7‐95.4] vs 46.5 [13.8‐75.9]; P = .014) than microfracture. Minimal clinically important difference achievement rates were higher with UCB‐MSCs‐HA for visual analog scale (50.0% vs 28.1%; P = .123), Western Ontario and McMaster Universities Osteoarthritis Index (53.1% vs 28.1%; P = .074), and International Knee Documentation Committee (56.3% vs 31.3%; P = .077) but were not significant. Lower limb alignment was not associated with clinical or MRI outcomes, and Magnetic Resonance Observation of Cartilage Repair Tissue scores did not differ between groups. Durable repair was more frequent with UCB‐MSCs‐HA (62.5% vs 26.3%, P = .031), and UCB‐MSCs‐HA was the only factor associated with durable repair (odds ratio 8.2, 95% confidence interval 1.6‐42.5, P = .012). Conclusions Allogeneic UCB‐MSCs‐HA implantation showed better clinical outcomes and a higher proportion of MRI‐defined durable repair tissue at 5 years compared with microfracture in osteoarthritic knees. Level of Evidence Level III, therapeutic retrospective comparison study.