Prognostic Factors in the Midterm Results of Pullout Fixation for Posterior Root Tears of the Medial Meniscus

PURPOSE: To identify predictors of unfavorable clinical and radiologic outcomes a minimum of 5 years after pullout fixation for medial meniscus posterior root tears (MMPRTs). METHODS: In total, 40 patients who were followed for >5 years after pullout fixation in MMPRT were recruited. The mean follow-up duration was 71.1 months. Clinical outcomes, including Lysholm score and International Knee Documentation Committee (IKDC) score, and radiographic results, including Kellgren-Lawrence (K-L; 0/1/2/3/4) grade and medial joint space width, were evaluated preoperatively and at final follow-up. Preoperative prognostic factors, including age, sex, body mass index, degree of varus alignment, K-L grade, medial joint space width, meniscal extrusion, and cartilage status, by the modified Outerbridge classification (grades 1 or 2 v 3 or 4), for relatively unfavorable (fair or poor grade) Lysholm or IKDC score, and progression of K-L grade were investigated by multivariate logistic regression analysis. RESULTS: The mean Lysholm score (52.1 ± 8.8 to 83.8 ± 11.9) and IKDC score (40.1 ± 7.6 to 73.3 ± 10.9) were improved significantly (P < .001), although the loss of medial joint space width (4.8 ± 1.1 to 3.9 ± 1.1 mm) and K-L grade (6/25/9/0/0 to 0/11/20/9/0) progressed significantly (P < .001). Unfavorable prognostic factors of the Lysholm score were grade ≥3 chondral lesions (odds ratio OR = 5.993; P = .028) and varus mechanical alignment (OR = 1.644; P = .017), for IKDC score were grade ≥3 chondral lesions (OR = 11.146; P = .038) and older age (OR = 1.200; P = .017). Preoperative chondral lesion grade ≥3 increased the risk of K-L grade progression (OR = 11.000; P = .031). CONCLUSIONS: Clinically, modified Outerbridge classification grade ≥3 chondral lesions, varus alignment, and older age were found to predict a poor prognosis after MMPRT fixation. In terms of radiographic K-L grade progression, grade ≥3 chondral lesions were identified as a poor prognostic factor. LEVEL OF EVIDENCE: Level IV, case series.