Bone Regeneration and Docking Site Healing After Bone Transport Distraction Osteogenesis in the Canine Mandible

Abstract

Purpose Bone transport distraction osteogenesis (BTDO) provides a promising alternative to traditional grafting techniques. However, existing BTDO devices have many limitations. The purpose of this research was to test a new device, the mandibular bone transport reconstruction plate (BTRP), in an animal model with comparable mandible size to humans and to histologically and mechanically examine the regenerate bone. Materials and methods Eleven adult foxhound dogs were divided into an unreconstructed control group of 5 animals, and an experimental group of 6 animals. In each animal, a 34 mm segmental defect was created in the mandible. The defect was reconstructed with BTRP. Histological and biomechanical characteristics of the regenerate and un-repaired defect were analyzed and compared to bone on the contralateral side of the mandible after 4 weeks of consolidation. Results The reconstructed defect was bridged with new bone, with little bone in the control defect. Regenerate density and microhardness were 22.3% and 42.6% lower than the contralateral normal bone, respectively. Likewise, the anisotropy of the experimental group was statistically lower than in the contralateral bone. Half the experimental animals showed non-union at the docking site. Conclusion The device was very stable and easy to install and activate. After one month of consolidation, the defect has been bridged with new bone with evidence of active bone formation. Regenerate bone was less mature than the control bone. Studies are underway to identify when the regenerate properties compare to normal bone, and to identify methods to augment bone union at the docking site.

Critical Sized Mandibular Defect Regeneration in Preclinical In Vivo Models

“…The articles which evaluated transport-disc-distraction osteogenesis used either internal or external distractors to attempt to bridge critical sized defects [17,18,21,49,50]. Authors carrying out TDDO on defects greater than 30 mm reported non-union rates between subjects at 50-100 % due to inadequate contact of the transport disc with the docking site [20,21].…”

“…Despite regeneration of the critical sized defect, the use of TDDO was not without complication. Complications encountered included infection and fracture of the fixation plates [17], tilting of the transport bone disc, mechanical malfunction of the distraction device, regenerated bone fracture, and wound dehiscence [20,21]. The most concerning complications reported were problems with transport disc docking.…”

“…Other studies reported high rates of non-union at the docking sites of the transport disc due to coned shaped bone outgrowths preventing adequate adaption of bone sites on contact. This led to failure rates ranging from 50 % [21] to 100 % [20] of animals. Thus, despite the benefits afforded with the use of TDDO, there still remains doubt regarding the strength of the regenerated bone, and the predictability of bone disc docking in animal models.…”

Application of a Novel Intraorally Customized Transport Distraction Device in the Reconstruction of Segmental Mandibular Defect

“…9 Despite the acceptable clinical results, using the transcutaneous pins to connect the device onto mandibular segments may cause several facial scars. 3,6 Whether using internal or external devices, an extraoral approach was performed for most transport distraction procedures according to the literature. Considering to avoid facial scar, an internal FIGURE 6.…”

“…1,2 Animal experiments and early clinical experience have confirmed that transport distraction osteogenesis can be used for the reconstruction of segmental bony defects. 3,4 However, most related publications reported an extraoral approach that resulted in obvious facial scars. 5,6 Only few reports used a customized design and custom-made distraction device to reconstruct the original geometric outline of the mandible.…”