Differences in Graft Tear Configurations in Medial and Lateral Meniscal Allograft Transplantation: Objective Evaluations Using Magnetic Resonance Imaging

Background:Few studies have compared the characteristics of meniscal allograft tears between medial and lateral meniscal allograft transplantation (MAT) using bone fixation.Purpose:To investigate the prevalence, location, and patterns of allograft tears after MAT with the bone fixation technique and compare tear patterns between medial and lateral compartments according to the time elapsed after surgery.Study Design:Cohort study; Level of evidence, 3.Methods:The charts of consecutive patients who underwent primary medial or lateral MAT between December 1996 and June 2019 were retrospectively reviewed. The location, pattern, and postoperative periods during which allograft tears occurred were evaluated by reviewing all series of follow-up magnetic resonance imaging (MRI) scans, which were performed at 6 weeks, 3 months, 6 months, and 1 year postoperatively and every 2 years thereafter with the patient's agreement. Postoperative periods for allograft tears were defined as the time between surgery and the follow-up MRI scan in which the meniscal tear was first confirmed. Allograft tears were compared between the medial and lateral MAT groups.Results:A total of 327 consecutive patients who underwent MAT (55 medial, 272 lateral) with a minimum 2-year follow-up were retrospectively reviewed. The incidences of allograft tears after medial and lateral MATs were 32.7% and 30.9%, respectively. The mean times for tears were 80.1 ± 81.1 months and 48.9 ± 46.3 months in the medial and lateral MAT groups, respectively ( P = .130). In both the medial and lateral MAT groups, allograft tears were observed mainly in the posterior horn, with complex tears being the most commonly identified tear type. In medial MATs, root tears were the second most common at 27.8%, with a significantly higher proportion than the lateral MATs ( P = .014). On the other hand, in lateral MATs, meniscocapsular separation and radial tears were the second most common at 15.5% each, albeit not significantly more common than in medial MATs ( P = .123 and P = .454, respectively). All root tears in medial MATs and meniscocapsular separations in lateral MATs were observed within 1 year postoperatively.Conclusion:Significant differences in allograft tear patterns were identified between the medial and lateral MAT groups. The proportion of root tears in medial MATs was higher than that in lateral MATs; conversely, the proportion of meniscocapsular separation was more common in lateral MATs. Such tear patterns, which may require surgical repair or graft resection, were observed only within 1 year of surgery. Therefore, close observation and regular follow-up in the earlier postoperative period are necessary after medial or lateral MATs.