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

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.

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.

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.

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.

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