Midterm Clinical and Radiological Outcomes of Revision Lateral Meniscal Allograft Transplantation.

Background: It is unknown whether the outcomes achieved in the early period after revision lateral meniscal allograft transplantation (RLMAT) are maintained through the midterm period. Purpose: To evaluate the midterm clinical and radiological results of patients who underwent RLMAT. Study Design: Case series; Level of evidence, 4. Methods: We reviewed the outcomes of 19 RLMATs in 18 patients with at least 5 years of follow-up data. The mean follow-up period was 6 ± 1.1 years (range, 5-8.5 years). Clinical outcomes were assessed using the modified Lysholm score, the International Knee Documentation Committee (IKDC) subjective score, and the Tegner activity level. Radiographic progression of arthritis was measured by the absolute and relative joint space widths on 45° of knee flexion posteroanterior radiographs preoperatively, 1 year postoperatively, and at the latest follow-up.Failure was defined as meniscocapsular separation, removal, or tear of more than half of the meniscal allograft on postoperative magnetic resonance imaging (MRI) or conversion to total knee arthroplasty. Of the 18 patients, 3 underwent ≥2 RLMATs. The survival rate was evaluated according to the number of revision surgeries. Results: For knees with an intact meniscus transplant at the final follow-up, the modified Lysholm and IKDC scores were significantly improved compared with preoperatively, but the Tegner activity level was unchanged. No significant differences were found in the absolute and relative joint space widths postoperatively. There were 6 failures within 3 years after RLMAT; the overall 5-year survival rate was 68.4% (13/19 knees). All failed knees showed bucket-handle tear patterns on MRI due to meniscocapsular healing failure. The survival rate decreased as the number of RLMATs increased-73.3% for a first RLMAT (n = 15 knees), 66.7% for a second RLMAT (n = 3 knees), and 0% for a third RLMAT (n = 1 knee). Midterm MRIs of 8 well-healed RLMATs showed evidence of meniscal degeneration; nonetheless, this did not affect clinical outcomes. Conclusion: The midterm results of RLMATs demonstrated a 5-year survival rate of 68.4% and positive clinical and radiological outcomes for failed MATs despite unimproved activity levels. Inadequate meniscocapsular healing was the leading cause of failure, and it needs to be carefully considered when performing RLMATs.