Partial Meniscectomy Provides No Benefit for Symptomatic Degenerative Medial Meniscus Posterior Root Tears

OBJECTIVES: Medial meniscus posterior root tears (MMPRTs) are recognized as a source of pain and dysfunction, but treatment options remain a clinical challenge. Currently, outcomes are unknown following partial meniscectomy for these lesions. To determine (1) the efficacy of partial meniscectomy to treat MMPRTs compared to a matched group of non-operatively treated MMPRTs, and (2) risk factors for worse clinical and radiographic outcome. METHODS: This retrospective comparative study was performed to include 27 patients with MMPRTs that were treated with arthroscopic partial meniscectomy (PMM) and a minimum 2-year follow-up. These patients were then matched by age, gender, and BMI to a group of 27 patients with MMPRTs treated non-operatively (control group). Demographic data, radiographic findings, final Tegner and IKDC scores were obtained and compared between the two groups. Risk factors for worse clinical and radiographic outcome in the PMM group alone, including age, sex, BMI, initial K-L grade, subchondral edema, and insufficiency fracture on MRI were determined. RESULTS: Overall, 54 patients were included in the study. 27 patients (10M: 17F) with a mean age of 55±9 and a mean BMI of 32.8±5.3 were treated with PMM and followed for a mean of 5.5±2 years (range 2.3-9.3 years). In the PMM group, final median Tegner score was 3, mean IKDC scores were 67.8±20, median KL grades on weight-bearing AP films demonstrated progressive arthritis (median grade 1 to 2, p=0.001) and more patients had grade II or higher arthritis at final follow-up than baseline (91.3% vs. 36% p<0.01. Overall, 14 of the 27 patients (52%) treated operatively progressed to total knee arthroplasty at a mean of 54.3 months. When comparing the PMM and control groups, there was no significant difference in final median Tegner scores, mean IKDC, median K-L grades, progression to arthroplasty, or overall failure rate. Following PMM, female patients had lower final IKDC scores (74.6±16.7 vs. 44.00±2.8, p=0.02) compared to males, as well as a higher rate of arthroplasty (70.6% vs, 20.0%, p=0.009). Higher BMI correlated with lower IKDC scores (r=-0.91, p=0.01) and meniscal extrusion was associated with higher rate of arthritis at final follow-up (100% vs. 57%, p=0.02). CONCLUSION: Partial meniscectomy for a MMRT provides no benefit in halting arthritic progression. Patients who undergo arthroscopic debridement for MMPRTs still progress to significant arthritis, poor clinical outcomes and a high arthroplasty rate (52%) at over 5-year follow-up. Compared to a non-operative control group, there was no benefit in any subjective or objective outcome measures from the arthroscopic partial meniscectomy. Female patients, higher BMI, and presence of meniscus extrusion were associated with worse outcomes and a higher rate of subsequent knee arthroplasty.