Anterior cruciate ligament injury versus tibial spine fracture in the skeletally immature knee: a comparison of skeletal maturation and notch width index.

Both midsubstance anterior cruciate ligament (ACL) injury and tibial spine avulsion fracture occur in the skeletally immature knee. The purpose of this study was to determine whether there are differences in skeletal maturation or notch parameters between these two groups. A retrospective case-control study of 25 skeletally immature patients with tibial spine fractures compared with 25 age- and sex-matched skeletally immature patients with midsubstance ACL injuries was performed. Bone age and notch width index were determined from preoperative radiographs. There were no significant differences between the tibial spine fracture group and the ACL injury group with respect to skeletal maturation, comparing bone age to chronological age (-0.5 vs. -0.3 years; P = 0.617). The ACL injury group had narrower notch indices than the tibial spine fracture group (0.230 vs. 0.253; P = 0.020). Thus, in a comparison of age- and sex-matched skeletally immature patients, those with midsubstance ACL injuries had a significantly narrower notch index than those with tibial spine fractures. This association may account for some of the variation in injury patterns in the skeletally immature knee.