Clinical Outcomes of Medial Meniscus Posterior Root Tears: High Rates of Subsequent Surgery and Worsening Arthritis at 5 Year Follow-Up

OBJECTIVES: Medial meniscus posterior root tears (MMPRTs) present a unique challenge for both patients and surgeons as these tears have shown to be biomechanically equivalent to complete meniscectomy. However, little is known about the natural history of these lesions. Therefore, the purpose of this study is to describe the clinical course of MMPRTs with respect to subsequent operative and non-operative treatments, and associated comorbidities. METHODS: Over 2600 MRIs were identified by searching radiologist reads for the terms “root” or “root tear” from 2005-2013. Presence or absence of MMPRTs and other associated boney, meniscal, or ligamentous injuries were identified and recorded. Of these MRIs, 102 MRIs from 102 patients who had unrepaired MMPRTs with minimum 2-year follow-up and no prior ligamentous surgery were followed. These MRIs were evaluated to confirm the presence of a meniscal root tear and the presence or absence of associated meniscal or ligamentous injuries, as well as meniscal extrusion, subchondral edema, or insufficiency fractures. Chart review was performed to obtain the treatment summary after diagnosis. Radiographs from before and after the diagnosis of MMPRT were reviewed and Kellgren-Lawrence scores were determined. Finally, the association between concomitant boney, ligamentous, or meniscal injuries, patient factors, and rate of arthroplasty, as well as final Kellgren-Lawrence scores were evaluated. Chi-square analysis was used for categorical variables, and Wilcoxon Rank-Sums was used for continuous variables. Kaplan-Meier analysis was used to evaluate the effect of meniscal extrusion on the time-dependant rate of arthroplasty. RESULTS: 104 patients (43 M:61F) were diagnosed with MMPRTs at a mean age of 54±13. These patients were followed for a mean of 66±26 months. 75 (74%) patients had associated meniscal extrusion, 64 (62%) had associated subchondral edema, and 14 (13%) had associated insufficiency fractures at the time of diagnosis. After initial diagnosis, 59 (58%) underwent subsequent surgical treatment. This included 52 (51%) patients undergoing arthroscopic partial meniscectomy, and 29 (28%) patients undergoing total knee arthroplasty at a mean 38±32 (range 3-107) months after MRI. Kellgren-Lawrence grades worsened from 1.3±0.7 before diagnosis to 2.2±1.0 after (p<0.001), with a mean 44±32 months between radiographs. There was a higher rate of radiographic arthritis (K-L grade 2+) after diagnosis (73%) than before diagnosis (36%) (p<0.001). The presence of meniscal extrusion on MRI was associated with the presence of arthritis on post-diagnosis radiographs (p=0.03). Meniscal extrusion, subchondral edema, and insufficiency fractures were not associated with increased rates of surgical treatment, or time to arthroplasty. CONCLUSION: Little information is available to guide patients and physicians on the clinical outcomes for MMPRTs. These injuries are associated with a relatively high rate of arthroplasty and worsening arthritis, especially with concomitant meniscal extrusion. More information is needed to determine the efficacy of meniscal root repair in preventing these unfavorable outcomes.