Evaluation of Meniscus Allograft Transplantation With Serial Magnetic Resonance Imaging During the First Postoperative Year: Focus on Graft Extrusion

Purpose: The purpose of this study was to evaluate change in meniscal allograft extrusion during the first year after meniscus allograft transplantation (MAT) by use of serial magnetic resonance imaging (MRI). Methods: Twenty-three consecutive patients who underwent MAT between June 2002 and March 2006 with total or subtotal meniscectomy of the knee were enrolled in the study. The medial meniscus was affected in 3 cases (15%) and the lateral meniscus in 18 cases (85%). Conventional MRI of the affected knee was performed in all 21 patients at 6 weeks and at 3, 6, and 12 months after MAT. We recorded subluxation at the 4 different time points by measuring the absolute value and relative percentage of extrusion (RPE), defined as the percentage of the width of extruded menisci compared with the width of the whole meniscus, using coronal images. We considered subluxation of greater than 3 mm to indicate extrusion. Results: The mean amount of graft subluxation on serial MRI was 2.87, 2.95, 3.03, and 2.96 mm at 6 weeks, 3 months, 6 months, and 12 months after MAT, respectively. The mean RPEs were 29.2%, 29.4%, 32.4%, and 31.9%, respectively. These values were not considered statistically significant among the 4 different time periods ( P > .05). Seven extruded cases (33.3%) at 6 weeks postoperatively remained extruded until the final follow-up at 1 year postoperatively. With 1 exception, the other 14 cases without extrusion at 6 weeks postoperatively did not undergo extrusion until 1 year postoperatively. Conclusions: A meniscus that extrudes early remains extruded and does not progressively worsen, whereas one that does not extrude early is unlikely to extrude within the first postoperative year. Level of Evidence: Level IV, therapeutic case series.