Medial Meniscus Posterior Root Repairs Performed With Modified Mason-Allen Locking Stitches Are Associated with Intact but Lax Repairs In A High Proportion of Cases Second Look Arthroscopy.

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 meniscus posterior root tears (MMPRTs).

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) morphological continuity between the bone bed and meniscus (intact versus non-intact) and 2) meniscal laxity on bony attachment by probing (lax versus non-lax). Healing conditions were categorized as follows: intact and non-lax tissue (group 1), intact and lax tissue (group 2), and healing failures (group 3). Clinical scores (Lysholm, Western Ontario McMaster Osteoarthritis Index [WOMAC], and the Knee injury and Osteoarthritis Outcome Score [KOOS]) and radiological outcomes (Kellgren-Lawrence grade and medial joint space width) were evaluated preoperatively and at the final follow-up.

Results: In total 34 patients (mean 58.2±6.1 years) were enrolled. In terms of healing conditions, intact root tissue and healing failure were observed in 33 (97%) and 1 (3%) patient, respectively. Among those with intact root tissue, 19 (56%) and 14 (41%) patients demonstrated non-lax tissue (group 1) and lax tissue (group 2) healing conditions, 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 minimal clinically important difference (MCID) for group 1 was as follows: Lysholm: 86.1±8.2 (MCID: 5.35), WOMAC: 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 of group 2; the group 2 scores were as follows: Lysholm: 76.8±7.0 (MCID: 2.85), WOMAC: 21.0±8.3 (MCID: 4.75), and KOOS: 32.8±10.0 (MCID: 6.5). Radiographically, group 1 exhibited significantly less K-L grade progression and less medial joint space narrowing than group 2.

Conclusion: Pullout repair utilizing modified Mason-Allen stitches demonstrated promising healing outcomes with a 97% intact root healing upon second-look arthroscopy. However, repairs that demonstrated laxity were associated with significantly worse PROMS, 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.