Posterior Horn Lateral Meniscal Oblique Radial Tear in Acute Anterior Cruciate Ligament Reconstruction Incidence and Outcomes After All-Inside Repair: Clinical and Second-Look Arthroscopic Evaluation

Background: The term posterior horn lateral meniscal oblique radial tear (LMORT) has emerged to characterize the tear patterns of the lateral meniscus in many patients with acute anterior cruciate ligament (ACL) injury. There is a lack of data regarding the exact incidence according to the types of LMORT and clinical outcomes. Purposes: (1) To investigate the incidence of LMORT according to type in patients with acute ACL reconstruction (ACLR) and (2) to identify healing status after repair of LMORT via second-look arthroscopy and clinical outcomes. Study Design: Case series; Level of evidence: 4. Methods: Patients who underwent primary ACLR within 6 months of injury were retrospectively reviewed. The LMORT was classified into 4 types based on the severity and distance from the root: type 1 (partial tear <10 mm from the root), type 2 (complete tear <10 mm from the root), type 3 (partial tear >10 mm from the root), type 4a (complete tear >10 mm from the root), and type 4b (type 4a with longitudinal tear at the meniscocapsular junction). Only patients with LMORT were isolated, and the clinical outcomes were compared according to the healing status of LMORT in second-look arthroscopy. Results: Of 635 patients with ACLR, LMORT was identified in 97 patients (15.3%), and type 4 LMORT accounted for the largest proportion (n = 62; 32.6%) of 190 lateral meniscal tears. In 79 patients with LMORT who satisfied the 2-year follow-up period, all patient-reported outcomes (PROs), including the Lysholm (preoperative, 64.1; postoperative, 88.2) and International Knee Documentation Committee subjective (preoperative, 50.5; postoperative, 82.9) scores, were significantly improved ( P < .001) 31.8 months postoperatively. Of the 61 patients who underwent second-look arthroscopy, 49 (80.3%) were classified into the complete healing group. There was no significant difference in postoperative PROs between the complete and partial healing groups. Conclusion: The incidence of LMORT was 15.3% in patients with acute ACL injury, and type 4 LMORT was the most common type. Complete healing of LMORT was achieved in 80.3% of patients who underwent second-look arthroscopy, and the PROs were significantly improved postoperatively. Good clinical results can be achieved if the LMORT is repaired as much as possible during ACLR.