Abnormal tibial alignment is a risk factor for lateral meniscus posterior root tears in patients with anterior cruciate ligament ruptures.

Purpose: The purpose of this study was to identify if abnormal tibial alignment was a risk factor for lateral meniscus posterior root tears (LMPRT) in patients with acute anterior cruciate ligament (ACL) ruptures.
Methods: The medical charts of 200 patients treated for ACL ruptures between 2013 and 2016 were retrospectively reviewed and evaluated. MRI images and reports were assessed for concurrent meniscal tears. Radiographs were reviewed for tibia vara and tibial slope angles and MRI reports identifying lateral root tears were compared to intraoperative reports to determine accuracy. Multiple logistic regression models were constructed to identify potential risk factors for LMPRTs.
Results: Of the 200 patients reviewed, a total of 97 individuals with concurrent meniscal injuries were identified. In patients sustaining a concurrent meniscal injury, there was a 4% incidence of medial meniscus posterior root tears and a 10.3% incidence of LMPRTs. Patients sustaining an ACL injury with an LMPRT were found to have greater tibia vara angles (4.2 ± 1.0 vs. 2.9 ± 1.7; p = 0.024), increased tibial slopes (12.6 ± 1.5 vs. 10.7 ± 2.9; p = 0.034), and higher BMIs (27.3 ± 2.9 vs. 25.3 ± 5.9; p = 0.034) when compared to patients without meniscus tears. There was low agreement between MRI and arthroscopic findings (kappa rate = 0.54). Multiple logistic regression analysis demonstrated that a tibia vara angle > 3 was associated with a 5.2-fold increase (95% CI 0.99-27.01; p = 0.050), and a tibial slope > 12 with a 5.4-fold increase (95% CI 1.03-28.19; p = 0.046) in LMPRTs.
Conclusions: Patients with greater tibia varus angles, increased tibial slopes, and higher BMIs were found to have an increased risk of LMPRTs when sustaining an ACL rupture. There was a low rate of agreement between MRI and arthroscopy in identifying LMPRTs. In patients with ACL ruptures who have abnormal tibial alignment or increased BMI, physicians should be watchful for lateral meniscus posterior root tears.
Level of Evidence: 3.