Knee anatomic geometry accurately predicts risk of anterior cruciate ligament rupture.

BACKGROUND: Certain anatomical characteristics of the knee have potential relationships with the risk of anterior cruciate ligament (ACL) rupture. There remains a need for stronger evidence using arthroscopy as well as radiological imaging to accurately clarify these relationships.

PURPOSE: To compare the anatomic geometry of the knee joint between patients with and without ACL ruptures.

MATERIAL AND METHODS: Case-controlled study of patients with arthroscopically confirmed ACL ruptures (ACL group) compared to patients with arthroscopically confirmed normal ACLs (control group). Magnetic resonance imaging scans were assessed for a total of 14 quantitative radiological variables including medial and lateral tibial slope angles (bone and cartilage measurements), meniscal height, femoral width, intercondylar notch width and tibial depth.

RESULTS: A total of 105 patients were included in the study, 55 in the ACL group and 50 in the control group. There was a significant difference ( P  < 0.05) of most of the radiological measurements between the two groups. There was also a significant difference ( P  < 0.05) when comparing the variables between sexes. Multiple logistic regression analysis produced a mathematical model utilizing all the radiological measurements with 92.6% classification accuracy in predicating an ACL rupture with the medial tibial slope angle being the strongest predicator variable (odds ratio = 8.97, P  = 0.011).

CONCLUSION: Greater postero-inferior directed slope measurements of bone and cartilage in both the lateral and medial compartments with a narrower intercondylar notch width increase the risk of ACL rupture. Mathematical modelling can accurately predict the risk of ACL rupture.