The posterior cruciate ligament inclination angle is higher in anterior cruciate ligament insufficiency

Purpose Magnetic resonance imaging (MRI) is the gold standard image examination for anterior cruciate ligament (ACL) lesion diagnosis. Our hypothesis was that measuring the posterior cruciate ligament inclination angle (PCLIA) using MRI images may be an auxiliary tool to aid the recognition of ACL insufficiency. The purpose of this study was to compare the PCLIA measurement in MRIs of individuals with and without ACL injury. Methods The PCLIA was measured by two radiologists in 65 knee MRIs of patients with intact ACL (control group) and in 65 knee MRIs of people with ACL injury (study group). In both groups, the posterior cruciate ligament was intact. The control group was included 35 men (53.8%) and 30 women (46.1%). The patients' average age was 38.7 years (range 15-75; SD +/- 14.8 years). In this group, 31 (47.6%) MRIs were from right knees and 34 (52.3%) were from left knees. The study group consisted of 45 men (69.2%) and 20 women (30.7%). The patients' average age was 36.8 years (range 14-55; SD +/- 10.3 years). In this group, 33 (50.7%) were right knees and 32 (49.2%) were left knees. PCLIA was formed by the intersection of two lines drawn in MRI sagittal images. The first passed tangentially to the articular surface of the tibial condyle and the second was drawn over the fraction of the ligament that originated where the first crossed the PCL, outlined proximally. Results The average PCLIA was 44.2 +/- 3.8 degrees in the control group and 78.9 +/- 8.6 degrees in the study group. Statistical analyses showed that the PCLIA was higher in the group with ACL injury (p < 0.05). Conclusion The PCLIA was significantly higher in individuals with ACL injuries. The measurement of this angle using MRI images may allow for detection of ACL insufficiency and thus assist in an individualized and precise approach to the treatment of injuries to the ACL. Level of evidence III.

Automated summary

MRI measurement of the posterior cruciate ligament inclination angle (PCLIA) may be an auxiliary tool in aiding the recognition of ACL insufficiency, with higher PCLIA values observed in individuals with ACL injuries compared to those without. This could potentially lead to more personalized and precise treatment approaches for ACL injuries.