Medial Meniscal Posterior Root Repairs Performed With Modified Mason‐Allen Locking Stitches Are Associated With Intact but Lax Repairs in a High Proportion of Second‐Look Arthroscopy Cases

PURPOSE: To investigate meniscal healing results and clinical outcomes based on healing status after root repair using modified Mason-Allen stitches with a locking mechanism from second-look arthroscopy in medial meniscal posterior root tears. METHODS: Among patients who underwent root repair between 2018 and 2022, those who consented to undergo second-look arthroscopy 1 year after surgery were recruited. The healing condition of the repaired meniscus was evaluated based on (1) morphologic continuity between the bone bed and meniscus (intact vs non-intact) and (2) meniscal laxity at the bony attachment by probing (lax vs non-lax). Healing conditions were categorized as follows: intact and non-lax tissue (group 1), intact and lax tissue (group 2), and healing failure (group 3). Clinical scores (Lysholm score, Western Ontario McMaster Osteoarthritis Index [WOMAC] score, and Knee Injury and Osteoarthritis Outcome Score [KOOS]) and radiologic outcomes (Kellgren-Lawrence grade and medial joint space width) were evaluated preoperatively and at the final follow-up. RESULTS: In total, 34 patients (mean age, 58.2 ± 6.1 years) were enrolled. In terms of healing conditions, intact root tissue and healing failure were observed in 33 patients (97%) and 1 patient (3%), respectively. Among those with intact root tissue, 19 patients (56%) and 14 patients (41%) showed non-lax tissue (group 1) and lax tissue (group 2), respectively. A significant improvement in clinical scores after surgery was noted in groups 1 and 2 but not in group 3. Regarding postoperative clinical scores, the mean values in group 1 were as follows: Lysholm score, 86.1 ± 8.2 (minimal clinically important difference [MCID], 5.35); WOMAC score, 12.8 ± 6.6 (MCID, 4.55); and KOOS, 22.4 ± 6.8 (MCID, 4.5). The group 1 outcomes were substantially better than those in group 2; the group 2 scores were as follows: Lysholm score, 76.8 ± 7.0 (MCID, 2.85); WOMAC score, 21.0 ± 8.3 (MCID, 4.75); and KOOS, 32.8 ± 10.0 (MCID, 6.5). Radiographically, group 1 exhibited significantly less Kellgren-Lawrence grade progression and less medial joint space narrowing than group 2. CONCLUSIONS: Pullout repair using modified Mason-Allen stitches showed promising healing outcomes with a 97% rate of intact root healing on second-look arthroscopy. However, repairs that showed laxity were associated with significantly worse patient-reported outcome measures and higher rates of progression of osteoarthritis. Considering that 23% of the total patients refused second-look arthroscopy, the possibility of transfer bias should be considered. LEVEL OF EVIDENCE: Level IV, retrospective case series.