Study on the correlation between posterior tibial slope measured by EOS biplanar imaging and anterior cruciate ligament injury

Objective To investigate the predictive efficacy of posterior tibial slope (PTS) evaluated by the three-dimensional imaging EOS system in patients with anterior cruciate ligament (ACL) injuries, and to compare its performance with three conventional X-ray techniques. Methods A retrospective analysis was conducted on clinical data from 51 patients diagnosed with ACL injury (ACL injury group) and 34 patients without ACL injuries (control group) treated at Nanjing Drum Tower Hospital affiliated to Nanjing University Medical School from October 2018 to December 2021. The PTS was measured using the EOS system, full-length, proximal, and posterior cortical techniques. Logistic regression analysis was employed to investigate the specificity of different methods in predicting ACL injuries. Results The PTS measurements of the ACL injury group by the EOS, full-length, and proximal method were statistically significantly different from those of the control group (P＜0.05). Logistic regression analysis yielded receiver operating characteristic (ROC) curves, with the EOS method achieving an area under the curve (AUC) of 0.955 and the full-length method reaching 0.657, both outperforming the proximal (0.558) and posterior cortex (0.484) methods. There was a correlation in the measurements of PTS by the EOS and full-length methods between the control group and the ACL injury group (r=0.612,r=0.641). Conclusions PTS measurements using the EOS system and full-length method based on lateral full-length X-rays are better than the proximal and posterior cortical techniques in predicting the susceptibility to ACL injuries. In hospitals without EOS facilities, the full-length method can serve as a reliable alternative for assessing patients' PTS.