Identification of Radiographic Parameters Associated with Anterior Cruciate Ligament Injury

Abstract

It is well established that limb alignment parameters such as increased knee valgus can be a risk factor for anterior cruciate ligament (ACL) injuries, and may play a role in failure after repair or reconstruction. Previous work has examined the association of some radiographic parameters from the patellar instability literature, which shares some of the same anatomic risk factors as ACL injuries. These have found mixed results regarding the predictive utility of these and related radiographic parameters when applied to ACL injuries, albeit with small sample sizes. The purpose of this study is to examine multiple radiographic parameters from the patellar instability literature in a large sample of ACL tears and compare these with a large cohort of age-matched controls. We hypothesized that alignment parameters reflective of knee valgus and rotational imbalance would be significantly higher in the ACL tear cohort. We also hypothesized that significant difference in these parameters would be observed in patients with meniscal injuries in addition to ACL tears. Consecutive cases of magnetic resonance imaging (MRI)-documented ACL ruptures were identified, along with an age-matched cohort of prospective controls with knee MRIs demonstrating intact ACLs and no meniscal pathology. Records of prospective controls were screened for a history of patellar instability, patellar maltracking, and/or patellofemoral pain syndrome. The presence of one or more of these diagnoses resulted in exclusion from the control group. All MRIs were reviewed by fellowship-trained musculoskeletal radiologist with more than 10 years of experience and familiarity with the radiographic parameters of interest. Seventeen parameters were measured on each MRI. Differences in central tendency between the ACL tear and control group were compared with Student’s t-test for normally distributed data or the Wilcoxon-Mann-Whitney test for nonparametric data, as determined by the Shapiro-Wilk test. Differences between controls and ACL tears with and without meniscal tears were assessed with the Kruskal-Wallis test, followed by Dunn’s post-hoc analysis when significant. The relationship between continuous and categorical variables was explored with logistic regression. Multivariable logistic regression analysis was conducted to determine which parameters, if any, were independent predictors of ACL injury. For the ACL injury cohort, multivariable regression was again conducted to determine independent predictors of concomitant meniscus tears (any tear, medial tear, lateral tear or both sides tear). Finally, receiver-operating characteristic (ROC) curves were constructed to determine which parameters were most predictive of ACL injury and ACL injury with or without associated meniscal injury. There were 161 patients with MRI demonstrating a torn ACL available for analysis, including 101 males (median age, 25; interquartile range [IQR], 18–31) and 60 females (median age, 26.5; IQR, 16.25–37). An age-matched cohort 65 males (median age, 26; IQR, 18.5–37) and 74 females (median age, 28; IQR, 16–37), 139 in total, served as controls. In univariate analysis, medial femoral condyle (MFC) width, lateral tibial plateau (LTP) width, and lateral femoral condyle (LFC) percentage were significantly higher in the ACL-tear cohort overall relative to controls, while medial tibial plateau (MTP) slope, LTP slope, and tibial tubercle-trochlear groove distance were significantly lower, though some variation was observed when stratified by sex (Tables 1 and 2). There were significant differences in MFC width, MTP width, MTP slope, LTP slope, TT-TG distance, LFC percentage, and MFC/MTP in patients with concomitant ACL and meniscus injuries (Table 3). Multivariable analysis revealed multiple parameters which were independently associated with ACL tears overall, ACL tears in males, ACL tears in females, ACL tears with concomitant meniscal tears (medial or lateral), ACL tears with concomitant lateral meniscus tears, and ACL tears with concomitant medial and lateral meniscus tears (Table 4). ROC analysis identified MTP slope as most predictive of ACL injury, overall as well as for males and females separately; age as most predictive of ACL with any concomitant meniscal injury, ACL with concomitant lateral meniscus injury, and ACL with both medial and lateral meniscus injury; and MFC width as most predictive of ACL with concomitant medial meniscus injury (Figure 1). In a large cohort of ACL tears with age-matched controls, our analysis identified multiple radiographic parameters which were significantly associated with ACL injuries when compared with the controls. Additionally, we identified significant differences and variation in these parameters among patients with ACL tears and concomitant meniscal injuries. These results may help identify anatomic risk factors which place some patients at relatively greater risk for failure after surgical treatment of ACL ruptures. Recognition of these risk factors could guide surgical decision making and rehabilitation protocols.