Experimental Model of Zygomatic and Mandibular Defects to Support the Development of Custom Three-Dimensional--Printed Bone Scaffolds.

[INTRODUCTION] Autologous reconstruction of segmental craniomaxillofacial bone defects is limited by insufficient graft material, donor site morbidity, and need for microsurgery. Reconstruction is challenging due to the complex three-dimensional (3D) structure of craniofacial skeleton. Customized 3D-printed patient-specific biologic scaffolds hold promise for reconstruction of the craniofacial skeleton without donor site morbidity. The authors report a porcine craniofacial defect model suitable for further evaluation of custom 3D-printed engineered bone scaffolds.

[METHODS] The authors created a 6 cm critical load-bearing defect in the left mandibular angle and a 1.5 cm noncritical, nonload bearing defect in the contralateral right zygomatic arch in 4 Yucatan minipigs. Defects were plated with patient-specific titanium hardware based on preoperative CT scans. Serial CT imaging was done immediately postoperatively, and at 3 and 6 months. Animals were clinically assessed for masticatory function, ambulation, and growth. At the 6-month study endpoint, animals were euthanized, and bony regeneration was evaluated through histological staining and micro-CT scanning compared to contralateral controls.

[RESULTS] All 4 animals reached study endpoint. Two mandibular plates fractured, but did not preclude study completion due to loss of masticatory function. One zygoma plate loosened while the site of another underwent heterotopic ossification. Gross examination of site defects revealed heterotopic ossification, confirmed by histological and micro-CT evaluation. Biomechanical testing was unavailable due to insufficient bony repair.

[CONCLUSIONS] The presented porcine zygoma and mandibular defect models are incapable of repair in the absence of bone scaffolds. Based on the authors' results, this model is appropriate for further study of custom 3D-printed engineered bone scaffolds.