Meniscal allograft subluxations are not associated with preoperative native meniscal subluxations

To determine the relationship between preoperative subluxation of the original menisci and postoperative graft subluxation after lateral meniscal allograft transplantation (MAT). Forty patients who underwent isolated lateral MATs in meniscus-deficient knees with a low-grade chondral lesion (≤ICRS grade 2) were assessed. Lateral subluxation of the native meniscus before meniscectomy and those of remaining meniscal tissue before MAT were measured on mid-coronal MRI scans taken at each time point. Postoperative meniscal subluxation was assessed using MRI at 6 months postoperatively, when the full rehabilitation protocols were completed. Correlation analyses were conducted to determine the associations between each of two preoperative lateral displacements and the postoperative graft subluxation. The mean lateral subluxations before primary meniscectomy and before MAT were 0.3 ± 1.0 mm and 0.2 ± 0.8 mm, respectively. At 6 months postoperatively, it was 2.3 ± 1.9 mm. There were no significant correlations between the preoperative subluxation at the two preoperative time points and the postoperative extrusion (Spearman rho 2-sided test: ρ = − 0.058, (n.s.) for the native meniscus; Pearson r 2-sided test, r = 0.309, (n.s.) for the remaining meniscal rim). Between the postoperative nonextruded and extruded groups, there were no significant differences for the preoperative subluxations. There are no associations between preoperative lateral subluxation of the native menisci and postoperative subluxation of meniscal transplants in patients who undergo MAT on the lateral compartment with low-grade arthritic changes. The extrusion phenomenon may be a distinct feature of transplanted menisci rather than an individual characteristic of meniscal displacement. Surgeons need to keep in mind that graft extrusion in nonarthritic knees might occur during transplantation. IV.