Arthroscopic Collagen Meniscus Implantation for Partial Lateral Meniscal Defects: A 2-Year Minimum Follow-up Study.

Background: Loss of knee meniscal tissue often leads to increased pain and decreased function. Hypothesis: At a minimum 2-year follow-up, patients receiving a lateral collagen meniscus implant (CMI) would show improved knee function and decreased pain compared with their preoperative status. Study Design: Case series; Level of evidence, 4. Methods: Twenty-four patients with irreparable lateral meniscal tears (n = 7) or previous partial lateral meniscectomy (n = 17) underwent arthroscopic lateral collagen meniscus implantation. Clinical evaluation was performed preoperatively, at 6 months, and at a minimum 2-year follow-up with Lysholm, visual analog scale (VAS) for pain, Tegner, objective International Knee Documentation Committee (IKDC), and EuroQol 5 dimensions (EQ-5D) scores. A magnetic resonance imaging (MRI) evaluation was performed preoperatively and at final follow-up using the modified Yulish score for cartilage and the Genovese score for implant size and signal intensity. Results: All clinical scores significantly improved from preoperative evaluation to final follow-up. Average Lysholm scores improved from 64.0 +/- 16.2 to 92.7 +/- 13.8 (P < .0001), VAS for pain from 55.2 +/- 29.4 to 19.5 +/- 25.6 (P < .0001), Tegner from 3 (interquartile range, 2-4) to 5 (interquartile range, 4-7) (P = .0062), objective IKDC from 6A, 14B, 4C to 20A, 3B, 1D (P = .0002), and EQ-5D from 0.58 +/- 0.28 to 0.89 +/- 0.14 (P < .0001). Good to excellent (A + B) objective IKDC scores improved from 83% preoperatively to 96% at 2-year follow-up. The Tegner index (the percentage of the lost activity level that was regained as a result of the treatment intervention) was 47% at 6-month follow-up and 79% at 2-year follow-up: this improvement was statistically significant (P = .0062). The MRI evaluations for tibial and femoral modified Yulish scores for cartilage remained similar over the course of the study; 87.5% of implants were reduced in size, and in 3 cases (12.5%), they were completely resorbed; 50% of the implants had a slightly hyperintense signal (relative to the normal meniscus), and signal intensity changes suggested that full maturation had occurred in 37.5% at final follow-up (based on the Genovese scores). Conclusion: The lateral CMI demonstrated that it was safe in this population study, with decreased pain and improved knee function in 96% of patients with excellent/good Lysholm results in 87% of patients at a minimum 2-year follow-up. The MRI scans demonstrated a decreased implant size relative to a normal meniscus.