Risk Factors Associated With Knee Joint Degeneration After Arthroscopic Reshaping for Juvenile Discoid Lateral Meniscus

Background: Although arthroscopic meniscal reshaping for discoid lateral meniscus (DLM) has better outcomes than total or subtotal meniscectomy, degenerative changes on radiographs are still seen in some patients with meniscal reshaping. Purpose: To assess the risk factors associated with knee joint degeneration after reshaping surgery for juvenile DLM. Study Design: Case-control study; Level of evidence, 3. Methods: Forty patients (45 knees) with a mean age of 12.0 years who underwent arthroscopic meniscal reshaping for DLM were enrolled at a mean of 39.6 months after surgery. For all patients, meniscal saucerization was performed first. Then, if the residual meniscus was unstable, stabilization was provided with suture fixation. At final follow-up, we obtained radiographs to assess degenerative changes to the knee joint using the classification by Tapper and Hoover. Residual meniscal width and meniscal extrusion (defined as a relative percentage of extrusion [RPE]) were measured with magnetic resonance imaging (MRI). Then, the correlation between radiographic evidence of degenerative changes (Tapper and Hoover grade), residual meniscal width, and RPE were assessed with Pearson and Spearman correlation analyses. Logistic regression analysis was used to examine whether preoperative characteristics correlated with degeneration and residual meniscal width. Results: The mean residual meniscal width was 4.6 mm (range, 3.8-6.0 mm), and the mean SD RPE was 25.5% +/- 21.8% at the final follow-up. There were 28 knees with Tapper and Hoover grade 0, 10 knees with grade 1, and 7 knees with grade 2. The residual meniscal width and RPE were significantly correlated with Tapper and Hoover grade ( = -0.489, P = .0007; = 0.414, P = .005, respectively). The residual meniscal width was also significantly correlated with RPE (r = -0.416, P = .004). The receiver operating characteristic curve showed that a 5.0-mm residual meniscal width was the cutoff value leading to evidence of degeneration. Multiple logistic regression analysis showed that an anterocentral shift on preoperative MRI was a risk factor for degeneration (odds ratio, 27.2; 95% CI, 1.1-360.5; P = .012) and residual meniscal width less than 5.0 mm (odds ratio, 20.9; 95% CI, 1.5-281; P = .022). Conclusion: Smaller meniscal width and greater severity of meniscal extrusion correlated with knee joint degeneration. An anterocentral shift on preoperative MRI was a risk factor for degenerative changes and smaller residual meniscal width.