Establishing signs for acute and healing phases of distal tibial classic metaphyseal lesions.

Background: Stages of healing for classic metaphyseal lesions (CMLs) are not well established. Follow-up skeletal surveys provide an opportunity to evaluate signs of healing CMLs.

Objective: To evaluate the sequence of CML healing phases by comparing initial and follow-up skeletal surveys in children with distal tibial CMLs on the initial survey. Findings could assist in child abuse investigations.

Materials And Methods: We identified all distal tibia CMLs with initial and follow-up skeletal surveys performed January 2009 through December 2018 at our institution. Two pediatric radiologists reviewed the surveys using Likert score from 1 (no CML) to 5 (definite CML). Only cases with score of 4 or 5 by both radiologists were selected for the study. The initial and 2-week follow-up skeletal surveys were reviewed in consensus for presence of the following signs: corner fracture, thin bucket handle fracture, thick bucket handle fracture, bucket handle fracture with endochondral bone filling the gap, subphyseal lucency, deformed corner, and subperiosteal new bone formation. We used the Kruskal-Wallis test to evaluate for significant difference in thickness among thin bucket handle fracture, thick bucket handle fracture, and bucket handle fracture with endochondral bone filling the gap.

Results: We included 26 children (12 girls) with age range 1-9.9 months who had a combined 34 distal tibia CMLs. Thin bucket handle fracture (n=13, 38.2%) was only seen on initial survey. On follow-up, six children had thick bucket handle fracture and four had bucket handle fracture with endochondral bone filling the gap. Fourteen thick bucket handle fractures (n=9) or bucket handle fractures with endochondral bone filling the gap (n=5) were noted on initial surveys; on follow-up, three (21.4%) had deformed corner, one (7.1%) had corner fracture, one (7.1%) had subphyseal lucency, and five (35.7%) were normal. None demonstrated thin bucket handle fracture on follow-up. Two of the nine (22.2%) thick bucket handle fractures became thicker, and 3/9 (33.3%) became bucket handle fractures with endochondral bone filling the gap. The metaphysis normalized in 8/34 (23.5%) CMLs on follow-up surveys. The thickness of thin bucket handle fracture was less than 1 mm (mean±standard deviation [SD] = 0.6±0.2 mm), which was significantly thinner (P<0.0001) compared with thick bucket handle fracture (1.7±0.5 mm) and bucket handle fracture with endochondral bone filling the gap (1.9±0.6 mm).

Conclusion: The lack of thin bucket handle fractures on any follow-up skeletal surveys suggests this sign represents an acute phase of injury. The next phases of healing appear to be thick bucket handle fracture followed by bucket handle fracture with endochondral bone filling the gap. It is important to note that normalization of the metaphysis at 2-week follow-up does not exclude CML because this was seen in about one-fifth of cases.