Partial Meniscectomy for Degenerative Medial Meniscal Root Tears Shows Favorable Outcomes in Well-Aligned, Nonarthritic Knees

Background: Arthroscopic meniscectomy has been commonly performed for persistent pain caused by degenerative medial meniscal posterior root tears (MMPRTs). However, risk factors that affect long-term outcomes and joint survivorship after meniscectomy are unclear. Purpose: To identify the risk factors associated with end-stage osteoarthritis after arthroscopic meniscectomy for degenerative MMPRT for middle-aged or elderly patients and to determine the joint survivorship according to the identified risk factors. Study Design: Case-control study; Level of evidence, 3. Methods: Data from 288 patients (24 male and 264 female), followed for at least 5 years after arthroscopic meniscectomy for degenerative MMPRTs performed between 1999 and 2010, were examined retrospectively. The modified Lysholm score was used for clinical evaluation. Cox proportional hazards regression analysis was used to assess factors that affect joint survivorship when conversion to total knee arthroplasty (TKA) was taken as the endpoint; these factors were age, sex, body mass index (BMI), preoperative tibiofemoral alignment (varus [<2° valgus] vs well-aligned [2°-10° valgus]), preoperative Kellgren-Lawrence grade (0 or 1 vs 2 or 3), and the modified Outerbridge grade of the medial compartment. Kaplan-Meier survival analysis and the log-rank test were used to compare overall survivorship with respect to each significant risk factor. Results: Mean age at the time of surgery was 58.9 years (range, 43-78 years). Sixty (20.8%) patients underwent TKA at 7.0 ± 3.6 years (range, 1.1-14.4 years) postoperatively. The mean follow-up time for those who did not undergo TKA was 8.9 ± 2.9 years (range, 4.5-16.5 years). The overall modified Lysholm score improved from 64.4 to 81.3 ( P < .001), but progression of radiographic arthritis was noted in 156 (61.9%) patients ( P < .001) at 2 years postoperatively. Age (hazard ratio [HR] = 1.049), BMI (HR = 1.092), varus alignment (HR = 2.283), and Kellgren-Lawrence grade 2 or higher (HR = 2.960) were significant risk factors for end-stage arthritis requiring TKA. Well-aligned nonarthritic knees (n = 131, 45.5%) survived significantly longer before requiring TKA than did knees with varus alignment or radiographic arthritis ( P < .05). The 5- and 10-year survival rates in these low-risk groups were 97.7% (95% CI, 95.2%-100.2%) and 89.1% (95% CI, 82.4%-95.8%), respectively. Conclusion: Arthroscopic meniscectomy is an effective treatment for degenerative MMPRTs, with favorable long-term survival in well-aligned nonarthritic knees. However, meniscectomy should be undertaken cautiously in patients with varus alignment and preoperative radiographic osteoarthritis.