Effect of Cyclic Compressive Forces on New Bone Formation during the Distraction Period in Mandibular Distraction Osteogenesis Using a Microactuator-Generated Distractor

Effect of the accordion technique on bone regeneration during distraction osteogenesis: A computational study

BACKGROUND AND OBJECTIVE

Distraction osteogenesis (DO), a bone lengthening technique, is widely employed to treat congenital and acquired limb length discrepancies and large segmental bone defects. However, a major issue of DO is the prolonged consolidation phase (10-36 months) during which patients must wear a cumbersome external fixator. Attempts have been made to accelerate the healing process of DO by an alternating distraction and compression mode (so-called "accordion" technique or AT). However, it remains unclear how varied AT parameters affect DO outcomes and what the most effective AT mode is.

METHODS

Based on an experimentally-verified mechanobiological model, we performed a parametric analysis via in silico simulation of the bone regeneration process of DO under different AT modes, including combinations of varied application times (AT began at week 1-8 of the consolidation phase), durations (AT was used continuously for 1 week, 2 weeks or 4 weeks) and rates (distraction or compression at 0.25, 0.5, 0.75, and 1 mm/12 h). The control group had no AT applied during the consolidation phase.

RESULTS

Compared with the control group (no AT), AT applied at an early consolidation stage (e.g. week 1 of the consolidation phase) significantly enhanced bone formation and reduced the overall healing time. However, the effect of AT on bone healing was dependent on its duration and rate. Specifically, a moderate rate of AT (e.g. 0.5 mm/12 h) lasting for two weeks promoted blood perfusion recovery and bone regeneration, ultimately shortening the healing time. Conversely, over-high rates (e.g. 1 mm/12 h) and longer durations (e.g. 4 weeks) of AT adversely affected bone regeneration and blood perfusion recovery, thereby delaying bone bridging.

CONCLUSIONS

These results suggest that the therapeutic effects of AT on DO are highly dependent of the AT parameters of choice. Under appropriate durations and rates, the AT applied at an early consolidation phase is beneficial for blood recovery and bone regeneration. These results may provide a basis for selecting effective AT modes to accelerate consolidation and reduce the overall treatment period of DO.

Regeneration of Craniofacial Bone Induced by Periosteal Pumping

A variety of surgical techniques and tissue engineering strategies utilizing osteogenic potential of the periosteum have been developed for the repair of extended bone deficiencies. The aim of the present study was to assess the impact of an alternating protocol of periosteal distraction osteogenesis (PDO) on bone regeneration in an intraoral model. Eight adult, male Beagle dogs were used for the study. Two distraction devices were placed on each side of the mandible. After a 7-day latency period, distraction devices in all animals were manipulated at the rate of 0.5 mm for a total of 8 days. The pumping protocol in two test groups proceeded twice daily by alternating activation with relaxation. In the periosteal pumping/distraction (PPDO) group, the distraction screws were activated two times (at 12 and 24 h) and then turned back (at 36 h), and in the periosteal pumping (PP) group repeatedly activated and turned back (at 12 h). In the PDO group, only activation was performed once daily (positive control). Devices were left inactivated in the negative control (NC) group. The samples were harvested after 8 weeks of consolidation period and investigated by micro-CT and histological analysis. New mature, lamellar bone was formed over the pristine bone in all groups. PPDO and PDO groups showed more new bone area (NBA) compared to the PP (p < 0.001 and p < 0.001, respectively) and to the NC group (p = 0.032 and p = 0.031, respectively). Furthermore, greater NBA was found in the PP group than the NC group (p = 0.006). PDO demonstrated higher relative connective tissue area than the PPDO group (p = 0.005) and lower relative new bone volume than the NC group (p = 0.025). Pumping protocol of periosteal distraction may successfully induce the endogenous regeneration of the mandibular bone in dogs. Impact Statement Repair of extended bone defects impose a significant challenge to oral and maxillofacial surgeons. In this article, a principle of distraction osteogenesis was applied to stimulate bone regeneration in the mandible. A periosteum-based regeneration approach may represent a valuable step toward creating a significant volume of hard and soft tissues, without need for autogenous bone harvesting or application of biomaterials.

Cyclic Distraction–Compression Dynamization Technique Enhances the Bone Formation During Distraction Osteogenesis

Background: Interfragmentary movements have benefits in the improvement of bone formation during distraction osteogenesis (DO). Although several clinical studies reported positive outcomes regarding the application of the cyclic distraction–compression (CDC) dynamization technique in cases with poor bone formation during DO, they are mostly anecdotal without a detailed description. The purpose of this study was to investigate the effectiveness and potential mechanism of different amplitudes and rates of the CDC technique on bone regeneration in a rat femur DO model.

Methods: A total of 60 adult male Sprague-Dawley rats underwent right femoral mid-diaphysis transverse osteotomy and were randomly and evenly divided into Control (no manipulation), Group1 (CDC therapy), Group2 (CDC therapy with larger amplitude), and Group3 (CDC therapy with a slower rate) after distraction. The CDC technique was performed during the middle phase of the consolidation period according to different protocols. Animals were sacrificed after 4 and 6 weeks of consolidation. The process of bone formation was monitored by digital radiographs, and the regenerate bone was evaluated by micro-computed tomography (micro-CT), biomechanical test, and histological analysis. The serum contents of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) were measured by enzyme-linked immunosorbent assay (ELISA).

Results: Bone regeneration after the CDC technique was improved significantly during DO. The digital radiograph, micro-CT, histomorphological analysis, and biomechanical evaluation showed better effects regarding volume, continuity, and mechanical properties of the regenerate bone in Group2 and Group3 when compared to Group1. The angiogenic and osteogenic markers were more highly expressed in Group2 and Group3 than in Group1 according to the immunohistochemical analysis. As for ELISA, the serum contents of HIF-1α and VEGF were also increased after the CDC technique, especially in Group2 and Group3.

Conclusion: The CDC dynamization technique has benefits on the improvement of bone formation during DO, and the mechanism may be due to tissue hypoxia activating the HIF pathway followed by the augmentation of osteogenic–angiogenic coupling. Better outcomes may be achieved by moderately increasing the amplitude and slowing down the rate of the CDC technique.