Mandibular transformations in prepubertal patients following treatment for craniofacial microsomia: Thin-plate spline analysis

To analyze correction of mandibular deformity using an inverted L osteotomy and autogenous bone graft in patients exhibiting unilateral craniofacial microsomia (CFM), thin‐plate spline analysis was undertaken. Preoperative, early postoperative, and ∼3.5‐year postoperative posteroanterior cephalographs of 15 children (age 10 ± 3 years) with CFM were scanned, and eight homologous mandibular landmarks digitized. Average mandibular geometries, scaled to an equivalent size, were generated using Procrustes superimposition. Results indicated that the mean pre‐ and postoperative mandibular configurations differed statistically (P < 0.05). Thin‐plate spline analysis indicated that the total spline (Cartesian transformation grid) of the pre‐ to early postoperative configuration showed mandibular body elongation on the treated side and inferior symphyseal displacement. The affine component of the total spline revealed a clockwise rotation of the preoperative configuration, whereas the nonaffine component was responsible for ramus, body, and symphyseal displacements. The transformation grid for the early and late postoperative comparison showed bilateral ramus elongation. A superior symphyseal displacement contrasted with its earlier inferior displacement, the affine component had translocated the symphyseal landmarks towards the midline. The nonaffine component demonstrated bilateral ramus lengthening, and partial warps suggested that these elongations were slightly greater on the nontreated side. The affine component of the pre‐ and late postoperative comparison also demonstrated a clockwise rotation. The nonaffine component produced the bilateral ramus elongations—the nontreated side ramus lengthening slightly more than the treated side. It is concluded that an inverted L osteotomy improves mandibular morphology significantly in CFM patients and permits continued bilateral ramus growth. Clin. Anat. 13:361–372, 2000. © 2000 Wiley‐Liss, Inc.