Graft Extrusion of 3 Millimeters Is Acceptable at a Minimum of 5-Year Outcomes for Lateral Meniscal Allograft Transplantation.

Purpose: To determine the acceptable amount of graft extrusion based on long-term radiographic outcomes in lateral meniscal allograft transplantation (MAT).

Methods: 94 lateral MAT patients with a minimum 5-year follow-up period were reviewed. Graft extrusion was measured on MRI scans taken 1 year after surgery, and the study population was divided according to the amount of extrusion: group A, extrusion <3 mm; group B, 3 mm ≤ extrusion <5 mm; and group C, extrusion ≥5 mm. For radiographic evaluation, the bilateral lateral joint space widths (JSWs) were measured on a standing 45° flexion posteroanterior radiograph. To standardize the measurements, the affected JSW was divided by the contralateral JSW. The change in the standardized JSW (ΔJSW) between the preoperative and latest follow-up assessments was analyzed according to the three groups. Multiple regression analysis was performed to control other related factors, such as lower limb alignment and cartilage status at the time of MAT. The acceptable amount of graft extrusion was calculated using a receiver operating characteristic (ROC) curve for the third quartile of ΔJSW. Clinical outcomes were evaluated using the Lysholm score and were compared among the groups.

Results: The mean follow-up duration was 8.3 ± 3.1 years. There were 54, 25, and 15 patients in group A, group B, and group C, respectively. In multiple regression analysis, both group B and group C had significant associations with ΔJSW and their beta coefficients were comparable (group B, P < .001, β = .642; group C, P < .001, β = 0.613). No significant difference in ΔJSW was found between group B and group C (P = .494). On the basis of the ROC curve, the acceptable amount of graft extrusion was 3.74 mm (sensitivity, 81.8%; specificity, 77.8%). There were no differences in the Lysholm scores among the three groups (P = .329).

Conclusions: ΔJSW differed between graft extrusion <3 mm (group A) and graft extrusion ≥3 mm (group B and group C). However, there was no significant difference in ΔJSW between group B and group C. No significant difference in clinical outcomes was found according to graft extrusion. This study gave supporting evidence for the currently recognized acceptable amount of graft extrusion (3 mm).

Level Of Evidence: Level III, retrospective cohort study.