Polyurethane meniscal scaffolds lead to better clinical outcomes but worse articular cartilage status and greater absolute meniscal extrusion

Purpose: Implantation of polyurethane (PU) meniscal scaffolds has become a popular procedure to provide a scaffold for vessel ingrowth and meniscal tissue regeneration in patients with partial meniscal defects. However, it is unclear whether PU meniscal scaffolds lead to better clinical and magnetic resonance imaging (MRI) outcomes post-operatively. This meta-analysis compared the clinical and MRI outcomes in patients with partial meniscal defects treated with PU meniscal scaffolds. Methods: This meta-analysis reviewed all studies that assessed Lysholm score, International Knee Documentation Committee (IKDC) score, visual analogue scale (VAS) for pain, Tegner score, Knee Injury and Osteoarthritis Outcomes Score (KOOS), articular cartilage (AC), absolute meniscal extrusion (AME), morphology and size (MS), signal intensity (SI) of meniscal implant, and interface of the implant–residual meniscus complex (IIRMC) in patients with partial meniscal defects treated with PU meniscal scaffolds. Results: Eighteen studies were included in the meta-analysis. The proportion of patients who evaluated MS (OR 0.71, 95% CI 0.38–1.33; n.s.), SI (OR 1.07, 95% CI 0.53–2.18; n.s.), and IIRMC (OR 1.00, 95% CI 0.33–3.06; n.s.) did not differ significantly between baseline and final follow-up. However, AC (OR 0.31, 95% CI 0.11–0.84; P = 0.02) and AME (OR 0.05, 95% CI 0.01–0.18; P < 0.00001) worsened between baseline and final follow-up. Conversely, Lysholm score (95% CI −1.87 to −1.07; P < 0.00001), IKDC score (95% CI −2.19 to −1.08; P < 0.00001), VAS for pain (95% CI −2.29 to −1.07; P < 0.00001), Tegner score (95% CI −0.76 to −0.15; P = 0.003), and overall KOOS (95% CI −29.48 to −23.17; P < 0.00001) were significantly greater at final follow-up when compared to baseline. Conclusion: This meta-analysis found no significant differences in the tested MRI parameters, including MS, SI, and IIRMC. However, AC and AME worsened between baseline and final follow-up. Conversely, patients treated with PU meniscal scaffolds showed significant functional improvement and pain relief when compared with baseline scores. Thus, PU meniscal scaffolds appear to be a viable alternative for patients with partial meniscal defects, although further studies are needed to determine whether worsened AC and AME are clinically relevant. In particular, precise measurement of PU meniscal scaffolds in combination with thorough investigation of the baseline articular cartilage status and meniscal defect size may be effective for pain relief or functional improvement in patients with PU meniscal scaffold implantation. Level of evidence: III.