Simultaneous Orthognathic Surgery and Costal Bone Grafting in Hemifacial Microsomia: A Rare Case Report and Literature Review.

Hemifacial microsomia (HFM) is a congenital craniofacial anomaly frequently associated with mandibular hypoplasia. Achieving stable correction in severe cases remains challenging due to abnormal mandibular anatomy and deficient temporomandibular joint structures. We report a rare revision case of a 20-year-old female with type IIA HFM who developed progressive postoperative resorption following two-jaw surgery, resulting in a "floating" ramus-condyle segment and subsequent recurrent facial asymmetry. Revision surgery consisted of unilateral sagittal split ramus osteotomy on the unaffected side, combined with long-plate fixation and costal bone grafting on the affected side. A distal portion of the harvested costal bone was trimmed and vertically split into smaller fragments and interposed as free bone grafts between the proximal and distal mandibular segments, while the main portion was applied laterally as an onlay graft. Postoperative follow-up confirmed preservation of mandibular height with an acceptable occlusion, and secondary fat grafting further refined the soft-tissue contour. This case suggests that integrating orthognathic surgery with autogenous bone grafting may provide a durable solution in complex revision scenarios. It also highlights the importance of individualized planning and combined skeletal-soft tissue approaches to achieve favorable aesthetics.