Posterior tibial slope angle in contact versus non-contact anterior cruciate ligament injuries.

Background: Increased Posterior Tibial Slope (PTS) angle has been reported to be a risk factor for primary anterior cruciate ligament (ACL) tears. However, it is unknown whether increased PTS has an associated increased risk for non-contact versus contact ACL injury.

Purpose: The purpose of this study is to determine whether patients with non-contact ACL injury have a higher PTS angle than those with contact ACL injury.

Methods: A total of 1700 patients who underwent primary ACL reconstruction between January 2011 and June 2023 at a single academic institution were initially included. Electronic medical records were reviewed for demographic information as well as evidence that the patient sustained a contact or non-contact ACL injury. Patients in the contact cohort were propensity score matched to patients in the non-contact cohort by age, sex and BMI. Additionally, patients in the contact cohort were then propensity score matched to a control group of patients with intact ACLs also by age, sex and BMI.

Results: One hundred and two patients with contact injury were initially identified and 1598 patients with non-contact injuries were identified. Of the 102, 67 had knee X-rays that were suitable for measurement. These 67 contact injury patients were propensity score matched to 67 noncontact patient and 67 patients with intact ACLs based on age, sex and BMI. There were no significant differences between contact and non-contact cohorts in age (28.7±6.3 vs. 27.1±6.5, p = 0.147), sex (Female: 36.0% vs. 34.3%, p = 0.858), or BMI (26.7±5.6 vs 26.1±3.4, p = 0.475). There was no significant difference in PTS angle between contact versus non-contact ACL injury patients (11.6±3.0 vs.11.6±2.8, p = 0.894). There was a significant difference in PTS between the contact ACL injury and the intact cohort (11.6±3.0 vs. 10.0±3.9, p = 0.010) and the non-contact ACL injury and the intact cohort (11.6±2.8 vs. 10.0±3.9, p = 0.010).

Conclusion: There was no significant difference in the degree of PTS between patients who sustained contact versus non-contact ACL injuries. Additionally, there was a significantly increased PTS in both the contact and non-contact ACL injury cohorts compared to patients with intact ACLs.