UCLA

Objective:  Hemifacial microsomia (HFM) is the second most common facial congenital anomaly. Distraction osteogenesis (DO) is one of the treatment modalities for patients with HFM and exhibits better post-op stability compared to other surgical modalities due to concurrent soft tissue expansion. Despite the increased popularity of DO, there is little research on its long-term outcome. Our objective was to evaluate changes in maxilla and mandible after distraction over twelve-year period.

Methods: Three HFM patients treated with DO were recalled at 9 time-points (T1-T9) over 12 years. The skeletal changes in chin position, maxillary width and height, occlusal height, and mandibular length were measured from posteroanterior cephalogram, 45° lateral oblique cephalograms, and cone-beam CT. Due to differences in traditional 2D radiographs (T1-T8) and 3D images from CBCT (T9), the ratio and angular measurements were used to evaluate the degree of asymmetry in addition to linear measurements. Effects on soft tissue were measured from photographs. Volume and surface analysis were proposed for future studies.

Results: Clinically significant improvements were seen after DO up to two-year post-DO (T7). Evaluations of the subsequent time-points revealed that with patient’s growth spurt, the skeletal growth of the affected, or experimental side lagged behind the unaffected, or control side, which served as control. The post-surgical recurrence of asymmetry was due to inherent growth potential difference rather than surgical relapse of DO. Twelve-year post-op (T9) showed that all patients had significant mandibular asymmetry compared to immediate post-op (T2). The degree of asymmetry at T9 was more severe than pre-op time-point (T1).

Conclusion: Even with overcorrection, due to the unpredictable and limited growth potential in the affected side, skeletal asymmetry worsened in HFM patient over 12 years post-DO.