Characterizing the Rate of Conversion to Total Knee Arthroplasty After Meniscal Allograft Transplantation

Background: Meniscal allograft transplantation (MAT) is often used to slow the progression of osteoarthritis and delay total knee arthroplasty (TKA). A comprehensive review summarizing the conversion rate to TKA after MAT is lacking in the literature. Purpose: To evaluate and characterize the rate of conversion to TKA after MAT in the current literature. Study Design: Systematic review; Level of evidence, 4. Methods: Scopus, PubMed, and Web of Science were queried from database inception to August 2024 for studies investigating outcomes of MAT. Included studies had to (1) include patients undergoing primary MAT, (2) define failure as conversion to TKA, and (3) report numbers of patients specifically undergoing TKA. Exclusion criteria included systematic reviews, meta-analyses, case reports, biomechanical studies, cadaveric studies, technique articles with no outcomes, studies that reported failure but did not specifically report conversion to TKA, no full text available, animal studies, and studies not in English. Patient demographics, conversion to TKA, demographics of patients who converted to TKA, follow-up time, and concomitant procedures were collected. Results: A total of 48 studies consisting of 4317 MATs in 4298 patients were included for analysis. Mean age ranged from 16.1 to 55.8 years old, mean body mass index ranged from 23.8 to 28.9 kg/m², and mean follow-up time was 6.9 years (range, 1.7-17.4 years). The range of conversion rates across the studies was 0% to 29.1%. The mean conversion rate in studies with mean follow-up time <5 years was 3.72% (n = 18), 5 to 10 years was 7.69% (n = 21), and >10 years was 12.82% (n = 9). In studies that reported the time to TKA conversion after MAT (n = 13), the mean was 10.1 years. The mean number of concomitant procedures per patient was 0.67 with the most common being chondral repair and ACL reconstruction. Zero studies evaluated only isolated MAT procedures. Conclusion: This study found that MAT can be durable and delay TKA for ≥10 years for nearly 90% of patients. This data can better inform patients and clinicians on outcome expectations. Studies with longer follow-up times had higher reported conversion to TKA. Thus, our study provides new data regarding longitudinal failure rates. While heterogeneity in the reporting of concomitant procedures with MAT allows for better generalizability, it makes it difficult to determine what effect these additional procedures have on rate of conversion to TKA.