Introduction

Numerous clinical and biomechanical studies demonstrate improved outcomes following repair of posterior root medial meniscus tears. However, few studies have investigated the preoperative clinical and radiologic factors that may be predictive of postoperative outcome following posterior root medial meniscus repair.

Methods

A retrospective cohort study was conducted among patients following isolated transtibial posterior root medial menisus repair performed by the senior author between October 2013 and June 2018. Three patient-reported outcome instruments were collected prospectively: Lysholm Knee Questionnaire (Lysholm), Marx Activity Scale (Marx), and the 12-Item Short Form Health Survey (SF-12). These surveys were initially administered preoperatively, then collected again at least two years following surgery.

Results

35 patients were eligible for inclusion (31 females, mean age: 51.1 ± 8.9 years, mean BMI: 31.8 ± 7.9). Average length of postoperative follow-up was 3.5 ± 1.4 years. Medial meniscus posterior root repair was associated with a statistically significant improvement in Lysholm (p < 0.0001) and SF-12 Physical Component scores (p < 0.0001), while Marx (p = 0.160) and SF-12 Mental Component scores (p = 0.283) failed to demonstrate statistically significant improvement. 61.1% of patients successfully returned to their pre-injury activity level (or higher), while 38.9% failed to return to the same level of activity after undergoing operative intervention. 88.9% of patients achieved the minimum clinically important difference (MCID) in Lysholm scores, 38.9% of patients achieved the MCID in Marx scores, and 100.0% of patients achieved the MCID in SF-12 Physical Component scores.

Older age was associated with a greater improvement in Marx scores from pre-op to post-op (p = 0.048) and was also predictive of achieving the MCID in this instrument (p = 0.023). African-American race predicted greater improvement in SF-12 Mental Component scores compared to Caucasian race (p = 0.004). An acute, traumatic injury mechanism was also associated with greater improvement in SF-12 Mental Component scores compared to an insidious, atraumatic onset of meniscal symptoms (p = 0.032). Greater knee range of motion preoperatively was predictive of better postoperative SF-12 Mental Component scores (p = 0.004), whereas obstructive sleep apnea predicted worse postoperative SF-12 Physical Component scores (p = 0.014). A history of cancer predicted worse postoperative Lysholm scores (p = 0.037).

With regard to the analysis of radiologic variables, greater medial joint space width on preoperative knee radiographs was predictive of achieving higher postoperative Marx scores (p = 0.013) and less meniscal extrusion on preoperative knee MRI was predictive of achieving the MCID in Lysholm scores (p = 0.047). Kellgren-Lawrence osteoarthritis grade, Modified Outerbridge cartilage grade, type of cartilage lesion (diffuse vs. focal), and location of cartilage lesion (unipolar vs. bipolar) were not associated with postoperative outcome scores (all p values > 0.05)

No postoperative complications were observed during the study period. 1 patient (2.9%) underwent reoperation on the ipsilateral knee due to persistent mechanical symptoms at 14 months post-op. Diagnostic arthroscopy at that time revealed no evidence of recurrent medial meniscus posterior root tear or other meniscal pathology.

Conclusions

While multiple prior studies have reported no association between age and postoperative outcomes in patients undergoing arthroscopic transtibial posterior root medial meniscus repair, our findings suggest that older age may be associated with a greater improvement in Marx scores as well as a higher likelihood of achieving MCID in the Marx Activity Scale. African-American race and having an acute, traumatic injury mechanism were both independently predictive of greater improvement in SF-12 Mental Component scores. Greater medial joint space width preoperatively predicted higher postoperative Marx scores, while less meniscal extrusion preoperatively predicted achieving the MCID in Lysholm scores.