Bone Healing Following Osseous Genioplasty is Minimally Impacted by the Osteotomy Gap Width

Background: Bone healing in the facial skeleton is impacted by the osteotomy gap and patient-specific factors. Factors that can impact ossification have not been completely characterized. Objectives: This study describes a technique for isolating the osteotomy region created in osseous genioplasty and characterizes factors impacting postoperative bone healing. Methods: Patients undergoing osseous genioplasty as part of facial feminization surgery were included in this study. All patients received sliding osseous genioplasty and had demineralized bone graft placed in the osteotomy gap. Immediate and 6-month postoperative CT images were used to generate 3D mandible models. After model alignment, the region immediately surrounding the osteotomy was isolated and bone volume and bone density [Hounsfield units (HU)] were measured. Results: In a cohort of 20 patients, between early and late imaging, bone volume increased significantly from 3857.3 cm 3 to 4261.6 cm 3 ( P =0.005) and bone density increased from 967.8 HU to 1134.8 HU ( P <0.001). On multivariable regression, bone healing as measured by change in bone density was decreased with a greater maximum osteotomy gap (b=−43.9, P =0.002) and increased with additional time between imaging points (b=20.3, P <0.001). Bone healing was not associated with patient age or smoking status. Conclusions: Bone healing in the osteotomy gap after osseous genioplasty is hindered by a large osteotomy gap at the midline. However, this difference is small relative to the difference in bone healing attributable to the increased time between imaging. The upper limit of the genioplasty gap that results in nonunion and unstable bone was not reached. Variation in bone fragment positioning to optimize aesthetic outcomes will not drastically impact the integrity of the healed bone.