Abstract
Background:
The native anterior cruciate ligament (ACL) changes in diameter and cross-sectional area throughout growth and up until age 18. The size and morphology of the native ACL continues to change throughout skeletal maturation. While ACL autografts have been shown to increase in size following ACL reconstruction in adults, there have been no similar studies to evaluate the change in ACL autografts in skeletally immature patients.
Purpose:
The primary aim of this study was to measure changes in ACL graft diameter in pediatric patients based on subsequent magnetic resonance imaging (MRI) after ACL reconstruction surgery. The second aim was to determine if there is evidence of ACL autograft growth after ACL reconstruction in skeletally immature patients.
Methods:
This was a retrospective review of 21 skeletally immature patients (mean age 14 years, range 12-16 years, 76% female) who underwent ACL reconstruction from January 2009 to July 2020 and had a subsequent MRI following surgery. We excluded patients who were treated with an allograft or underwent subsequent MRI for ACL re-injury. We measured the mid-substance ACL cross-sectional area and the post-operative graft diameter on subjects’ subsequent MRI. The recorded intra-operative graft diameter was compared to the post-operative graft diameter to determine the change in graft size.
Results:
76% (n=16) of subjects were treated with a quadriceps autograft. Follow-up MRIs were performed at a mean of 1.7 years (range 0.3 – 3.8 years) post-operative. Post-operative grafts increased 2.2mm (p<0.001, 95% CI = 1.8-2.7) in diameter compared to the intra-operative graft diameter (Figure 1).
Conclusions:
In our study population, there was a significant increase of 2.2mm in ACL graft diameter an average of 1.7 years after ACL reconstruction in skeletally immature patients. Our results are similar to previous studies demonstrating an increase in graft size post-operatively in adults. These results suggest that it may be useful for surgeons to take the likely changes in graft size into account when determining appropriate autograft size in skeletally immature patients.
Comparison between initial mid graft diameter measurement size and follow-up MRI graft diameter size. The line within the box defines the median value. The range of the box defines the 25th and 75th percentile, and whiskers extending from the box plots define the range of measurements obtained.