Prognostic Factors of Arthroscopic Pull-out Repair for a Posterior Root Tear of the Medial Meniscus

Background: Repair of a posterior root tear of the medial meniscus (MRT) decreases peak contact pressure by restoring hoop tension and is expected to prevent progression to osteoarthritis. Purpose: The purposes of this study were (1) to report the clinical and magnetic resonance imaging (MRI) results of arthroscopic pull-out repair of the MRT and (2) to identify prognostic factors of poor outcome. Study Design: Case series; Level of evidence, 4. Methods: Fifty-one patients (47 women, 4 men) who underwent arthroscopic pull-out repair of the MRT by a single surgeon were enrolled. Mean follow-up after surgery was 33 months (range, 24-44 months). To identify factors affecting final outcome, patient-specific factors, such as gender, age, body mass index, meniscus extrusion, extrusion increase, subchondral edema, degree of varus alignment (<5 degrees or >5 degrees), and cartilage status in the medial compartment (Outerbridge grade 1 or 2 lesion vs grade 3 or 4 lesion), were investigated. Final clinical outcomes were determined using a visual analog scale (VAS) for pain and patient satisfaction scores, American Knee Society (AKS) scores, and Lysholm scores, and MRI outcomes were determined by evaluating meniscus extrusion and articular cartilage status. Multiple regression analysis was performed to identify variables that independently affected clinical and MRI-determined outcomes. Results: All clinical outcome measures significantly improved after surgery. Patients with Outerbridge grade 3 or 4 chondral lesions had poorer results than those with grade 1 or 2 lesions in terms of AKS function and Lysholm scores. Patients with varus alignment of >5 degrees had poorer results than those with varus alignment of <5 degrees in terms of VAS satisfaction, AKS function, and Lysholm scores. Mean meniscus extrusion increased from 3.6 mm preoperatively to 5.0 mm postoperatively. Chondral lesions progressed in 3 (9.7%) of 31 patients. Preoperative meniscus extrusion was found to be positively correlated with final extrusion. Conclusion: At a mean follow-up of 33 months after pull-out repair, extrusion of the meniscus was found to have progressed. Nevertheless, this technique provided patients with a clinical benefit. Outerbridge grade 3 or 4 chondral lesions and varus alignment of >5 degrees were found to independently predict an inferior clinical outcome.