The Creation and Validation of an Ankle Bone Age Atlas and Data Predicting Remaining Ankle Growth

Background: The purpose of the current study was 2-fold: (1) to create and validate an ankle bone age atlas spanning the pediatric and adolescent years and (2) to utilize this atlas in conjunction with distal tibia/fibular growth data as measured on serial radiographs to develop a predictive growth model for the lower extremity.

Methods: Radiographs were surveyed to identify distinguishable, reproducible, radiographic features. Radiographic features of the tibia, fibula, hindfoot, and midfoot from 270 patients were identified and a "standard" for each age/sex was selected to create an atlas. A separate cohort of 90 ankle radiographs was selected to validate the atlas. A subcohort of 41 patients with left-hand radiographs within 3 months of ankle imaging was used to compare the 2 bone age approaches. Harris growth lines were evaluated in 304 serial images of the distal tibia to determine the remaining growth.

Results: The distal tib/fib ossification centers provided the best age assessment for early childhood (male age: 1 to 8 y; female age: 1 to 4 y). The ossification/fusion of the calcaneal apophysis provided the best age assessment in the preadolescent stage (male age: 6 to 14 y; female age: 5 to 12 y). The closure of the distal tib/fib physes best determined skeletal maturity (male age: 14 to 16 y; female age: 12 to 14 y). The ankle atlas had excellent interobserver and intraobserver reliability (intraclass correlation coefficient=0.993, P <0.001 and 0.998, P <0.001), respectively. We found an excellent correlation between the patient's chronologic age and ankle bone age ( r =0.984; P <0.001). Ankle bone age assessment and Greulich and Pyle were correlated ( rs =0.822, P <0.001). We found that males with a bone age of ≥15 years and females with a bone age of ≥13 years had ≤2 mm of residual growth of the distal tibia/fibula physes.

Conclusions: bone age can be determined using ankle films ordered to assess/treat ankle injuries. This tool, along with our growth remaining table, may have important clinical implications when managing patients with ankle trauma with premature physeal closure.

Level of evidence: IV.