Changes of functional units in type IIA craniofacial microsomia before puberty-a preliminary computed tomography study.

Background: The natural growth of the mandible in craniofacial microsomia (CFM) remains a topic of considerable debate. This study aims to characterize the mandibular architecture and its natural growth in children with type IIA CFM using functional unit analysis.

Materials and methods: 16 sets CT data of 8 unoperated children with unilateral IIA CFM with an interval ranging from 2 to 6 years (3.4±1.5 years,AVR±SD)were collected. The baseline skeletal units' discrepancy in size, annual growth, and angular measurements were analyzed.

Results: The condylar, coronoid, and body units were smaller (reaching 63%, 79%, and 90% of the unaffected side, respectively) while the angular unit was larger on the affected side. The condylar unit on the affected side grew slower than the unaffected side, at about 60% of its rate, and other units showed no statistically significant bilateral differences. The backward rotation angle of the affected body unit (BUA) increased from T1 to T2.

Conclusion: This preliminary study suggests that the condyle unit is the center of mandible deformity in type IIA CFM and exhibits insufficient growth relative to the unaffected side . Meanwhile, the hemi-mandible on the affected side rotated posteriorly during growth, thus worsening spatial relation. Future studies with larger sample sizes that incorporate clinical assessments are needed to elucidate the progression of CFM.