Treatment of Painful, Irreparable Partial Meniscal Defects With a Polyurethane Scaffold: Midterm Clinical Outcomes and Survival Analysis

Background: A biodegradable polyurethane scaffold was designed to fulfill a challenging clinical need in the treatment of patients with painful, irreparable partial meniscal defects. Hypothesis: The use of an acellular polyurethane scaffold for new tissue generation in irreparable, partial meniscal defects provides both midterm pain relief and improved functionality. Study Design: Case series; Level of evidence, 4. Methods: A total of 44 patients with irreparable, partial meniscal defects (29 medial and 15 lateral) were implanted with a polyurethane scaffold in a prospective, single-arm proof-of-principle study with a minimum 5-year follow-up. Clinical outcomes were measured with the visual analog scale (VAS) for pain, International Knee Documentation Committee (IKDC), and Knee injury and Osteoarthritis Outcome Score (KOOS) at baseline and at 2- and 5-year follow-up. Magnetic resonance imaging (MRI) was used to evaluate the meniscal implant and cartilage status of the index compartment. Kaplan-Meier time-to-treatment failure distributions were also performed. Removal of the scaffold, conversion to a meniscal transplant, or unicompartmental/total knee arthroplasty was used as endpoints. Results: Seven patients were lost to follow-up (15.9%). The patients who participated in this study showed significant clinical improvement after surgery (mean [SD] at baseline, 2 years, and 5 years: 56.2 +/- 21.6, 24.6 +/- 22.7, and 19.3 +/- 26.9, respectively [VAS]; 206.5 +/- 79.7, 329.8 +/- 108.9, and 333.6 +/- 112.2, respectively [total KOOS]). MRI of the scaffolds showed a smaller sized implant when compared with the native meniscus with an irregular surface at 2- and 5-year follow-up. A stable cartilage status of the index compartment at 5-year follow-up was demonstrated in 46.7% of patients compared with the baseline status. During the follow-up period, 62.2% of the implants survived. At final follow-up, 66.7% of the medial scaffolds were still functioning versus 53.8% of the lateral scaffolds. Conclusion: A polyurethane meniscal implant can improve knee joint function and significantly reduce pain in patients with segmental meniscus deficiency up to 5 years after implantation. A stable cartilage status of the index compartment at 5-year follow-up was demonstrated in 46.7% of patients, calling into question the chondroprotective ability of the implant. In addition, a relatively high failure rate was noticed. Long-term and randomized controlled studies are mandatory to confirm the initial results and the reliability of this procedure.