Evaluation of a Segmental Titanium Implant for Mandibular Reconstruction Using a Critical Size Defect Model in the Dog--A Pilot Study

Abstract

Craniomaxillofacial trauma and tumor resection are common causes of large mandibular defects in human beings and animals. Restoration of function and occlusion via rigid fixation is the goal of reconstructive procedures for unstable fractures and segmental defects. The aims of this pilot study were to describe the use of a porous titanium alloy implant (Regenerex) in comparison to cortical strut allografting techniques in the repair of critical size defects (CSD) in the dog edentulous mandible and report upon the operative technique and complications encountered with the procedures and novel application of this porous titanium alloy. Ten purpose-bred, male and female adult mongrel dogs between 2 to 3 years of age, weighing 20-25 kg, and without evidence of craniomaxillofacial or systemic disease had left sided dental extractions extending from the mandibular canine tooth to the last molar. Once healed, a 40mm segmental ostectomy was performed and repaired with a 2.0 locking titanium reconstruction plate augmented with either an interfragmentary cortical strut allograft (n=5) or the Regenerex implant (n=5). Dogs were euthanized and mandibles harvested for gross evaluation and histopathology. Osteointegration occurred in the 3 month Regenerex implanted dog only. The cortical strut allograft implanted animals demonstrated new bone formation and incorporation of the allograft in all but 1 dog that experienced plate breakage. The use of a porous titanium alloy implant designed to facilitate osteointegration for canine mandibular reconstruction following creation of a critical size defect has not been previously reported. Osteointegration could not be demonstrated in patients beyond three months postoperatively. The authors suspect inadequate contouring of the implant to be responsible for the failure.