Evaluation of Posterior Tibial Slope for Anterior Cruciate Ligament Tear and Meniscal Tear: A Cross-sectional Study

Introduction: The Posterior Tibial Slope (PTS) is an angle formed by the tibial plateau and supports the biomechanics of the knee joint. This slope is found to be a factor in differentiating ACL tear injuries. Earlier studies have shown the association of PTS with Anterior Cruciate Ligament (ACL) tears, but have not evaluated the PTS values for different gradings.

Aim: To evaluate the PTS on X-ray and Magnetic Resonance Imaging (MRI), for patients with different grades of ACL tears, and patients identified with meniscal tears.

Materials and Methods: This cross-sectional study was conducted from April 2020 to March 2021 at the Department of Radiodiagnosis and Imaging, KS Hegde hospital, Mangaluru, Karnataka, India. A total of 30 patients were studied, in which 20 patients with ACL tears underwent both X-ray and MRI, while the 10 patients with meniscal tears were only subjected to MRI. The PTS was evaluated for different grades of ACL tears on X-ray and MRI by an experienced Radiologist. The number of patients with grade I, grade II, and grade III ACL tears were 7, 6 and 7, respectively. Paired t-test was used to evaluate the mean PTS for the identified grade of the ACL tear. One-way Analysis of Variance (ANOVA) and Bonferroni’s post-hoc test was used to analyse the difference between grades of the ACL tear.

Results: The mean age of the study population was 32.50±16.363 years, and the male-to-female ratio was 4:1. Both right, as well as the left knee, were included in the study, and the left-to-right knee ratio was 3:2. There was a significant difference in PTS between Grades of ACL tears (p-value-0.001). The PTS was observed to increase as the severity of the ACL injury increased.The mean PTS value obtained on X-ray for grade I, grade II, and grade III ACL tears were 10.85±0.54, 14.18±0.62, and 16.46±1.56, respectively. While the mean PTS value obtained on MRI for grade I, grade II, and grade III ACL tears were 10.85±0.53, 14.19±0.60, and 16.47±1.55, respectively. There was no significant difference in the PTS measured for ACL tears between the X-ray and MRI (p-value >0.05). Further, the results did not show any difference of significance in the PTS measured on MRI between ACL tears and meniscal tears (p-value >0.05).

Conclusion: The PTS can be used as an aid in the identification of the severity of the ACL injury. The PTS could also be used as a tool to recognise the presence of ACL tears on X-ray and this could be an important prognostic factor towards the functional outcome.