Impact of the Posterior Tibial Slope on Medial Meniscus Posterior Root Tear Healing Based on Second-Look Arthroscopy

Abstract

Background:

Although a steep posterior tibial slope (PTS) has been reported to cause medial meniscus root tears, few studies have investigated whether the PTS affects healing outcomes

Purpose/Hypothesis:

This study aimed to investigate the influence of PTS on the healing status of repaired medial meniscus posterior roots via second-look arthroscopy. It was hypothesized that a steeper PTS is associated with an increased risk of compromised meniscal healing.

Study Design:

Case series; Level of evidence, 4.

Methods:

Patients who underwent isolated root repair using modified Mason-Allen sutures between 2019 and 2023 and consented to second-look arthroscopy at 1 year postoperatively were included. The primary endpoint was the morphological healing status characterized as lax versus nonlax tension. Patients were classified into group 1 (nonlax: stable during probing without separation; n = 29) and group 2 (lax: displacement during probing; n = 21). The anatomic PTS was primarily assessed using preoperative lateral radiographic views. Additionally, the medial PTS (MPTS) and lateral PTS (LPTS) were evaluated using preoperative magnetic resonance imaging of the central slices of the respective medial and lateral tibial plateaus. The PTS, MTPS, and LTPS were compared between the 2 groups. The cutoff value associated with lax healing was confirmed.

Results:

The PTS values (mean ± standard deviation) were 6.6°± 3.3° for group 1 and 9.3°± 2.5° for group 2, demonstrating a significantly elevated PTS in group 2 compared with group 1 (effect size, 0.484; 95% CI, 0.237 to 0.672; P = .001) The MPTS value was 5.4°± 3.2° in group 1 and 8.6°± 3.0° in group 2, with a significantly greater PTS in group 2 (effect size, 0.490; 95% CI, 0.245 to 0.676; P = .001). The LPTS value was 4.9°± 2.4° in group 1 and 5.8°± 2.7° in group 2; however, it did not differ significantly (effect size, 0.216; 95% CI, −0.066 to 0.467; P = .126). Based on the cutoff values, a PTS of ≥8.3° (P = .004) and an MPTS of ≥7.7° were identified as a PTS associated with lax healing (P = .001).

Conclusion:

An increased PTS may contribute to lax healing, which in turn progresses to meniscal extrusion after root repair. Consequently, when performing root repair in patients with an increased PTS, it can be anticipated that the postoperative healing and clinical outcomes may not be as favorable as those in patients without an increased PTS.