Wayne Ozaki

Volume maintenance of onlay bone grafts in the craniofacial skeleton: Micro-architecture versus embryologic origin

&NA; The superior volume maintenance of membranous over endochondral bone has been shown in several studies and provides the basis for its preferred clinical use as an onlay grafting material in the craniofacial skeleton. The scientific rationale for this seeming embryologic advantage, however, has never been proven. Our hypothesis is that the pattern of onlay bone graft resorption is primarily determined by a grafts micro‐architecture (relative cortical and cancellous composition) rather than its embryologic origin (membranous versus endochondral). Twenty‐five adult New Zealand, White rabbits were used for this study. Eight animals were killed at 3 weeks, eight animals at 8 weeks, and nine animals at 16 weeks. Three graft types were placed onto each rabbit cranium: cortical bone graft of membranous origin and cortical and cancellous bone graft of endochondral origin. Fluorochrome markers were injected into all living rabbits at 1, 6, and 14 weeks. Microcomputed tomography scanning was performed on all of the bone grafts to determine postsacrifice volumes and to obtain detailed information regarding the bone grafts trabecular architecture. In addition, specimens were examined histologically. Volume analysis showed a statistically greater resorption rate in the cancellous endochondral bone graft than in either the endochondral or membranous cortical bone grafts (p < 0.05) for all time points. In addition there was no significant difference in the resorption rates between the endochondral and membranous cortical bone grafts. A post‐test power analysis (alpha = 5 percent) of the volume data comparing the two types of cortical bone grafts showed that a difference in resorption of 8.9 percent would be detected with a 90‐percent probability. Previous studies, which have shown a seeming superiority of membranous over endochondral bone grafts, used composite grafts composed of both cortical and cancellous portions. By separating these components, we have shown that cortical bone grafts maintain their volumes significantly better than cancellous bone grafts. In addition, we found no statistical difference in the resorption rates between the two cortical onlay bone grafts of different embryologic origins, a finding that has never been previously published. From our results, we believe cortical bone to be a superior onlay grafting material, independent of its embryologic origin. We believe these results challenge the currently accepted theories of bone graft dynamics and may lead to a change in the way clinicians approach bone graft selections for craniofacial surgery. (Plast. Reconstr. Surg. 102: 291, 1998.)

Biomechanical Study of Sternal Closure Using Rigid Fixation Techniques in Human Cadavers

BACKGROUND We believe rigid plate fixation may be superior to wire fixation in sternal closure, as rigid fixation used in the craniofacial skeleton has shown greater stability, lower postoperative pain, and accelerated bone healing. We hypothesize that sterna fixed with titanium plates are more stable mechanically than sterna fixed with wires. METHODS The sterna from human cadavers were used in this two-phased study. Phase I compared wires to four-hole titanium straight plates. Phase II compared wires to four-hole titanium custom H plates. The sterna were tested biomechanically using all fixation methods. RESULTS Phase I showed no statistically significant difference in the stiffness or lateral displacement between the wired and straight plated sterna. Phase II showed a statistically significant greater stiffness (p < 0.05) and less lateral displacement (p < 0.05) in the custom plated sterna over the wired sterna. CONCLUSIONS Our results showed that custom titanium H plates were superior to wire fixation. Furthermore, our results established the importance of plate configuration in sternal fixation. Our study may have beneficial clinical implications, as decreased motion at the sternotomy site could mean less postoperative pain, a decreased incidence of infection, and accelerated bone healing.

investigation of the Influences of Biomechanical Force on the Ultrastructure of Human Sagittal Craniosynostosis

&NA; This study presents comparisons of the ultrastructure of synostotic and open portions of synostotic sagittal sutures using histomorphometry, scanning electron microscopy, and microcomputed tomography. By using stereologic and histomorphometric analysis, this study proposes to demonstrate evidence of the influence of biomechanical force on the suture during the process of sagittal craniosynostosis. Finally, we propose to link the pathologic changes transforming normal suture fusion to craniosynostosis with concurrent changes in the polarity of suture fusion initiation. Seven infants (four boys and three girls) with sagittal craniosynostosis, ranging in age from 1.4 to 4.8 months (mean = 3.0 months), underwent sagittal synostectomies. The synostotic bone specimens were sectioned into three regions: an open suture, partial synostosis, and complete synostosis. Microcomputed tomographic and scanning electron microscopic scanning as well as histomorphometry was performed on all specimens to obtain detailed qualitative and quantitative information regarding the trabecular microarchitecture of the synostosed suture. Microcomputed tomographic analysis determined the bone volume fraction, trabecular thickness, trabecular separation, bone surface to bone volume ratio, and anisotropy for all specimens. Our results showed significant differences in all of these quantitative measurements when comparing the complete synostotic suture with the open portion of the synostotic sutures (p < 0.05). Microcomputed tomographic stereologic analysis showed evidence of the influence of biomechanical force on the synostotic and open portions of the synostotic sutures. Results of scanning electron microscopy show a definite qualitative difference in the trabecular pattern of the partial and complete synostotic suture when compared with the open portion of the synostotic sagittal suture. In this study, we performed both qualitative and quantitative comparisons of the ultrastructure of the complete synostotic and nonsynostotic sagittal sutures using stereologic and histomorphometric techniques. We also demonstrated evidence of the influence of biomechanical force on the synostotic sagittal suture. Finally, we established a link between the pathologic changes transforming normal suture fusion to craniosynostosis and concurrent changes in both the vector and direction of suture fusion initiation. (Plast. Reconstr. Surg. 102: 1385, 1998.)

Reduction of Rib Fractures With a Bioresorbable Plating System : Preliminary Observations

BACKGROUND Operative fixation of rib fractures can reduce morbidity and mortality. Currently, resorbable fixation devices are used in a variety of surgical procedures. METHODS A standard osteotomy was prepared in 30 New Zealand white rabbits at the 12th rib. Eighteen had surgical repair with bioresorbable plates and 12 underwent nonoperative management. Half the animals in each group were killed at 3-week postfracture and the remaining animals were killed at 6-week postfracture. Ribs were radiographed and processed histologically to assess fracture healing. Rib reduction was defined as the alignment of the rib ends in a structural condition similar to the prefractured state and quantitative radiomorphometry measured the radiopaque callus surrounding the rib injury sites. Statistical analysis was performed using Fishers exact test and an unpaired Students t test and significance was established at p < 0.05. RESULTS At both the 3- and 6-week intervals, seven of the nine rib fractures remained reduced in the operative group, whereas zero of six and three of six of the rib fractures remained reduced, respectively, in the nonoperative group. A statistically significant increase in radiopaque callus surrounding the rib injury sites was observed at 3 and 6 weeks in the fixed groups. CONCLUSIONS Fixation of rib fractures with a bioresorbable miniplate system was superior to nonoperative treatment at the 3-week interval, with a statistically significant increase in radiopaque callus formation at both 3 and 6 weeks. Additional studies will evaluate the biomechanical outcomes and degradation tissue response after extended in vivo intervals.

RhBMP-4 gene therapy in a juvenile canine alveolar defect model

Background: Autologous bone grafts have the disadvantages of donor-site pain and morbidity, finite supply, increased costs, and prolonged hospitalizations. Using a juvenile canine model, the authors hypothesized that recombinant human (rh) bone morphogenetic protein (BMP)-4 gene therapy–treated alveolar defects would promote bone healing and canine tooth eruption equal to their autografted counterparts. Methods: Sixty-five maxillary alveolar defects were created in juvenile foxhound dogs with a mean age of 80.8 days. Nineteen defects were treated with DNA plasmid encoding rhBMP-4, 16 defects were autografted, 15 defects contained scaffold only, and 15 defects were left unrepaired. At 4 and 12 weeks after surgery, bone density and tooth eruption were measured, respectively. Data were subjected to one-way analysis of variance testing with statistical significance established at p < 0.05. Results: At 4 weeks, the bone densities in the rhBMP-4, autografted, scaffold-only, and defect-only groups were 31.2 ± 6.5, 30.5 ± 8.1, 18.4 ± 3.8, and 15.2 ± 4.0 percent, respectively. A significant effect (p < 0.05) was observed between the rhBMP-4 gene therapy–treated and autografted groups compared with the scaffold-only and defect-only groups. At 12 weeks, the rates of tooth eruption measured in the rhBMP-4, autografted, scaffold-only, and defect-only groups were 67.4 ± 15.8, 58.3 ± 18.8, 52.7 ± 16.2, and 45.0 ± 13.3 percent, respectively. A significant effect (p < 0.05) was observed between the rhBMP-4 gene therapy–treated and defect-only groups. Conclusions: In the present studies, rhBMP-4 gene therapy was equivalent to autografting and superior to the scaffold-only and unrepaired defect in bone regeneration and tooth eruption. With decreased morbidity and cost, rhBMP-4 gene therapy may ultimately become an alternative to autografting to repair bony defects.

Quantitative Comparison of Volume Maintenance between Inlay and Onlay Bone Grafts in the Craniofacial Skeleton

Background: Nonvascularized autologous bone grafts are the criterion standard in craniofacial reconstruction for bony defects involving the craniofacial skeleton. The authors have previously demonstrated that graft microarchitecture is the major determinant of volume maintenance for both inlay and onlay bone grafts following transplantation. This study performs a head-to-head quantitative analysis of volume maintenance between inlay and onlay bone grafts in the craniofacial skeleton using a rabbit model to comparatively determine their resorptive kinetics over time. Methods: Fifty rabbits were divided randomly into six experimental groups: 3-week inlay, 3-week onlay, 8-week inlay, 8-week onlay, 16-week inlay, and 16-week onlay. Cortical bone from the lateral mandible and both cortical and cancellous bone from the ilium were harvested from each animal and placed either in or on the cranium. All bone grafts underwent micro–computed tomographic analysis at 3, 8, and 16 weeks. Results: All bone graft types in the inlay position increased their volume over time, with the greatest increase in endochondral cancellous bone. All bone graft types in the onlay position decreased their volume over time, with the greatest decrease in endochondral cancellous bone. Inlay bone grafts demonstrated increased volume compared with onlay bone grafts of identical embryologic origin and microarchitecture at all time points (p < 0.05). Conclusions: Inlay bone grafts, irrespective of their embryologic origin, consistently display less resorption over time compared with onlay bone grafts in the craniofacial skeleton. Both inlay and onlay bone grafts are driven by the local mechanical environment to recapitulate the recipient bed.

Use of scanning electron microscopy in the evaluation of craniosynostosis.

The cause of craniosynostosis continues to elude researchers. Although several studies have looked at the ultrastructure of normal suture closure, no previous studies have examined the microarchitecture of the synostotic suture. Our goal was to assess the scanning electron microscope (SEM) as a viable and useful tool in examining craniosynostosis. Our hypothesis is that the SEM is a powerful analytical tool that can evaluate nonsynostotic, partial synostotic, and complete synostotic cranial sutures. We analyzed the cranial suture of 3 human infants with nonsyndromic sagittal craniosynostosis. The specimens were separated into three groups, which included regions of partial and complete synostosis and a region of open suture. Histological examination provided cellular and tissue data about craniosynostosis, whereas the SEM provided detailed information regarding the trabecular microarchitecture of the synostosed suture. The SEM produced quality images of complete and partially synostotic sutures and open sutures. At low magnification, the SEM characterized the general bony microarchitecture of cranial sutures in a manner different from, but complementary to, standard histological sections. At higher magnification, the SEM allowed us a look at the cellular population of craniosynostotic sutures in a way that surpasses standard light microscopy. The SEM is an excellent tool for the study of craniosynostosis and has proved invaluable in our ability to evaluate the microarchitecture and cellular population of the fusing suture. We believe we have proven our hypothesis by demonstrating the SEM to be a powerful analytical tool that can evaluate nonsynostotic, partial synostotic, and complete synostotic cranial sutures.

Use of Resorbable Fixation System in Pediatric Facial Fractures

INTRODUCTION Resorbable fixation system (RFS) is an alternative to titanium in open reduction and internal fixation of pediatric facial fractures. METHODS This study retrospectively reviewed all medical records in a major metropolitan pediatric hospital in Cape Town, South Africa from September 2010 through May 2014. Inclusion criteria were children under the age of 13 with facial fractures who have undergone open reduction and internal fixation using RFS. Intraoperative and postoperative complications were reviewed. RESULTS A total of 21 patients were included in this study. Twelve were males and 9 were females. Good dental occlusion was achieved in all patients and there were no complications intraoperatively. Three patients developed postoperative implanted-related complications: all 3 patients developed malocclusions and 1 developed an additional sterile abscess over the right zygomatic bone. For the latter, incision and drainage was performed and the problem resolved without additional operations. DISCUSSION Resorbable fixation system is an alternative to titanium products in the setting of pediatric facial fractures without complications involving delayed union or malunion. The combination of intermaxillary fixation and RFS is not needed postoperatively for adequate fixation of mandible fractures. Resorbable fixation system is able to provide adequate internal fixation when both low-stress and high-stress craniofacial fractures occur simultaneously.Introduction: Resorbable fixation system (RFS) is an alternative to titanium in open reduction and internal fixation of pediatric facial fractures. Methods: This study retrospectively reviewed all medical records in a major metropolitan pediatric hospital in Cape Town, South Africa from September 2010 through May 2014. Inclusion criteria were children under the age of 13 with facial fractures who have undergone open reduction and internal fixation using RFS. Intraoperative and postoperative complications were reviewed. Results: A total of 21 patients were included in this study. Twelve were males and 9 were females. Good dental occlusion was achieved in all patients and there were no complications intraoperatively. Three patients developed postoperative implanted-related complications: all 3 patients developed malocclusions and 1 developed an additional sterile abscess over the right zygomatic bone. For the latter, incision and drainage was performed and the problem resolved without additional operations. Discussion: Resorbable fixation system is an alternative to titanium products in the setting of pediatric facial fractures without complications involving delayed union or malunion. The combination of intermaxillary fixation and RFS is not needed postoperatively for adequate fixation of mandible fractures. Resorbable fixation system is able to provide adequate internal fixation when both low-stress and high-stress craniofacial fractures occur simultaneously.