P0823 - Can the Posterior Cruciate Ligament (PCL) Predict Anterior Cruciate Ligament (ACL) Size for Planning During ACL Reconstruction?

Background: Pediatric Anterior Cruciate Ligament reconstruction (ACLR) has increased over the past several years. In general, a graft size of 8mm is the accepted minimal size for adult ACLR, since literature suggests higher revision rates with grafts <8mm. Reproducing the native ACL size parameters would ideally inform graft size in pediatric patients, however, there is limited literature on the appropriate graft size in this population. If ACL size could be accurately estimated based on preoperative imaging, it may be possible to individualize ACL graft size to each patient.


Purpose: To establish a correlation between the ACL and PCL size in normal pediatric knees, with the goal of informing appropriate graft size for ACL reconstruction.


Methods: Normal knee MRIs of 200 females and 200 males ages 13-18 were assessed. Measurements included (Figure 1): ACL and PCL length (sagittal view), thickness (AP dimension in sagittal plane), and width (transverse dimension in axial plane). Thickness and width was measured in each ligament at the femoral origin, midsubstance, and tibial insertion. ACL footprint thickness and width along tibial insertion was also measured. Inter-rater reliability of the above measurements was assessed with a random set of 25 patients. Pearson correlation coefficients were used to assess the correlation between the ACL and PCL measurements. Linear regression models were used to test whether the relationship between the ACL and PCL measurement differed by sex or age.

Results: Demographic data from 400 patients are shown in Table 1. Inter-rater reliability was high for all measurements except PCL thickness at midsubstance. ACL and PCL length were positively correlated (r=0.59, p<0.0001). ACL and PCL femoral origin width were negatively correlated (r=-0.33, p<0.0001). ACL and PCL midsection thickness were positively correlated (r=0.15, p=0.0003). ACL and PCL midsection width were positively correlated (r=0.22, p<0.0001). ACL and PCL tibial insertion thickness were positively correlated (r=0.24, p<0.0001). ACL and PCL tibial insertion width were positively correlated (r=0.37, p<0.0001). Correlation between ACL and PCL length, as well as correlation between ACL and PCL insertion thickness, was moderated by sex and age. The correlation between ACL and PCL midsection thickness, as well as the correlation between ACL and PCL midsection width was moderated by sex. The correlation between ACL and PCL insertion width was moderated by age. Mean ACL/PCL ratio for width @ midsubstance = .45 +/- .14, and for length = .86 +/- .096.

Conclusions: Correlations exist between ACL and PCL measurements, with some moderated by sex and/or age. This study is the first step in potentially informing normal ACL size in pediatric patients based on an intact PCL on MRI.