Three‐dimensional magnetic resonance imaging analysis shows sex‐specific patterns in changes in anterior cruciate ligament cross‐sectional area along its length

Abstract

Smaller anterior cruciate ligament (ACL) size in females has been hypothesized to be a key contributor to a higher incidence of ACL tears in that population, as a lower cross-sectional area (CSA) directly corresponds to a larger stress on the ligament for a given load. Prior studies have used a mid-length CSA measurement to quantify ACL size. In this study, we used magnetic resonance imaging to quantify the CSA along the entire length of the intact ACL. We hypothesized that changes in the ACL CSA along its length would have different patterns in males and females. We also hypothesized that changes in ACL CSA along its length would be associated with body size or knee size with different associations in females and males. MR images of contralateral ACL-intact knees of 108 patients (62 females, 13-35 years) undergoing ACL surgery were used to measure the CSA along the ACL length, using a custom program. For both females and males, the largest CSA was located at 37%-39% of ACL length from the tibial insertion.Compared to females, males had a significantly larger CSA only within the distal 41% of the ACL (p < 0.001). ACL CSA was associated with patient height and weight in males (r > 0.3; p < 0.05), whereas it was associated with intercondylar notch width in females (r > 0.3; p < 0.05). These findings highlight the importance of standardizing the location of measurement of ACL CSA.

Changes in the Cross-Sectional Profile of Treated Anterior Cruciate Ligament Within 2 Years After Surgery

“…Interestingly, we did not find any significant associations between graft CSA and height or BMI, after controlling for false discovery rate. This finding is in agreement with similar associations between CSA profile of the native ACL and weight, 21 as well as several previous studies suggesting weight as a predictor of hamstring autograft size. 3 , 20 , 29 , 38 Similar to weight, knee size (bicondylar width) was also associated with graft CSA along almost the entire graft length within the first year after surgery and along the midsubstance of the graft at 2 years.…”

“… 14 , 15 , 26 A custom MATLAB script (MathWorks) was developed to turn the segmented ligaments ( Figure 1B ) into 3D point clouds ( Figure 1C ). 21 The program used linear regression to approximate the ligament longitudinal axis in the sagittal plane ( Figure 1C ).…”

“…A subset of contralateral native ACL MRI scans used in this study were previously used to comprehensively assess the CSA profile of the native ACLs using the same approach. 21 …”

“…A subset of contralateral native ACL MRI scans used in this study were previously used to comprehensively assess the CSA profile of the native ACLs using the same approach. 21 MRI scans were also used to measure bicondylar width and intercondylar notch width using techniques described previously. 14,25 Briefly, intercondylar notch width was measured in the coronal plane, parallel to a line along the most inferior aspects of the femoral condyles.…”