Effect of Preoperative Joint Space Width on Lateral Meniscal Allograft Transplantation: Outcomes at Midterm Follow-up

Background: It remains unclear whether lateral joint space narrowing without severe cartilage loss before meniscal allograft transplantation (MAT) affects clinical outcomes and graft extrusion. Hypothesis: Patients with greater preoperative joint space narrowing would show more graft extrusion, more osteoarthritis progression, and worse clinical outcomes than would those with less narrowing. Study Design: Case-control study; Level of evidence, 3. Methods: We retrospectively evaluated 61 patients who underwent lateral MAT and had a minimum follow-up of 4 to 5 years. The median preoperative joint space width (JSW) on Rosenberg view radiographs was used to classify patients into those with less joint space narrowing (JSW >= 3 mm; group A) and greater joint space narrowing (JSW <3 mm; group B). We compared differences between groups in terms of graft extrusion and articular cartilage loss (modified Outerbridge grade >= 3) on 1-year postoperative magnetic resonance imaging (MRI) scans and changes in JSW and clinical outcomes at the last follow-up. Results: There were 31 patients in group A and 30 patients in group B; the mean follow-up time for all patients was 64.4 +/- 10.3 months. All patients showed a significant preoperative to postoperative improvement in outcome scores (P < .001 for all). The mean preoperative JSW was 3.8 +/- 0.9 mm in group A and 2.3 +/- 0.4 mm in group B (P < .001). In group B, there was more graft extrusion on postoperative MRI scans (3.0 +/- 0.9 vs 1.9 +/- 0.6 mm, respectively; P < .001) and a higher proportion of patients with pathological graft extrusion at final follow-up (43.3% vs 12.9%, respectively; P = .011) compared with group A. At 1 year postoperatively, cartilage loss grade >= 3 was observed at the lateral femoral condyle in 3.2% and 20.0% of patients in groups A and B (P = .053), respectively, and at the lateral tibial plateau in 3.2% and 30.0% of patients (P = .006), respectively. There were moderate correlations between graft extrusion and preoperative absolute JSW (r = -0.471; P < .001) and preoperative relative JSW (r = -0.428; P = .001). Conclusion: Patients with less preoperative joint space narrowing had less graft extrusion and cartilage loss on 1-year postoperative MRI scans, as well as better radiological and clinical outcomes at midterm follow-up, compared with patients with greater preoperative narrowing.