The Effect of Bony Parameters on the Pediatric Knee: Normal versus Anterior Cruciate Ligament Injury versus Tibial Spine Avulsion Fracture.

Anterior cruciate ligament (ACL) injuries can present as a ligamentous disruption or avulsion fracture of the tibial spine in pediatric patients. Differences in knee morphometric parameters have been investigated between pediatric cohorts with ACL disruptions and tibial spine avulsion fractures. However, no study to date has compared morphometric parameters in patients with tibial spine avulsion fracture against a control population.  A retrospective review of pediatric patients undergoing knee magnetic resonance imaging (MRI) studies was performed, identifying 15 patients with tibial spine avulsion fracture between January 1, 2009, and January 1, 2013. Inclusionary criteria consisted of patients who sustained an acute tibial spine avulsion fracture and had MRI examination. The MRI studies were analyzed by a pediatric musculoskeletal radiologist, who measured identified bony parameters, and results were compared with an age-matched control group and a skeletally immature cohort with ligamentous disruption of the ACL. Data were analyzed using unpaired test and logistic regression.  Cohorts included 15 patients with a tibial spine avulsion fracture, 39 with an ACL disruption, and 28 in the age-matched control group. The tibial spine group demonstrated no significant differences in bony parameters when compared with the control group, but had significantly wider tibial eminence widths in comparison to the ACL group (2.92 cm [0.4] versus 2.71 cm [0.27];  = 0.040). Additionally, this finding was predictive of tibial spine avulsion injury when assessed by logistic regression.  Pediatric patients who sustain a tibial spine avulsion fracture exhibit significantly wider tibial eminences when compared with the cohort with ACL injuries. This indicates a possible biomechanical explanation for differences in ACL injury patterns that should be examined in future, prospective analyses.