RESUMO
The superior volume maintenance of membranous over endochondral bone grafts, which was shown in several studies has provided the basis for its preferred clinical use as an onlay grafting material on the craniofacial skeleton. The scientific rationale for this seeming embryological advantage, however, has never been proven, Since the cortical component of membranous bone is proportionally greater than that of endochondral bone, it follows that membranous grafts would show greater volume maintenance over time. Our hypothesis is that the pattern of onlay bone graft resorption is primarily determined by a graft's micro-architecture (relative cortical and cancellous composition) rather than its embryololgical origin(membranous versus endochondral). Fourty adult New Zealand white rabbits were used for this study. There were 8 animals in each of 4 groups. The rabbits of each group were sacrificed at 3, 8, and 16 weeks. Four types of grafts were placed subperosteally, onto each rabbit's cranium: a hydroxyapatite, a cortical bone graft of membranous origin, a cortical bone graft of endochondral origin and a cancellous bone graft of endochondral origin. Membranous bone grafts were obtained from the lateral mandible and endochondral bone grafts were obtained from the ileum. In order to determine post-sacrifice volume and density of the bone grafts, a caliper technique and bone densitometry(bone densitometer: LUNAR, DPX-L, U.S.A.) were performed on all of the bone grafts. Bone graft specimens were histologically examined at 3, 8, and 16 weeks.The measurement of volume and density show that there is a statistically greater resumption in the cancellous endochondral bone grafts for all parameter, compared to either the endochondral or membranous cortical bone grafts or hydroxyapatite at all time points(p< 0.05). In addition, there is no significant difference in the resorption rates between the endochondral and membranous cortical bone grafts for all parameters at all time points. By placing cortical bone grafts and cancellous bone grafts on the recipient sites separately, we have shown that the former grafts maintain their volumes, widths and projections significantly better than the latter grafts. Futhermore, we found no statistical difference in resorption rates between the two cortical bone grafts of different embryologic origins, a finding which has never been previously shown. Bone volume fraction, measured with bone densitometry, was shown to be higher in cortical bone than in cancellous bone at all time points, further illustrating the differences between cortical and cancellous bone.From our results, we believe cortical bone to be a superior onlay-graftiong material, independent of its embryololgic origin.
Assuntos
Adulto , Animais , Humanos , Coelhos , Fatores Biológicos , Densitometria , Durapatita , Íleo , Restaurações Intracoronárias , Mandíbula , Esqueleto , Crânio , TransplantesRESUMO
Based on our experience with 23 frontotemporal reconstructions performed, this paper attempts to provide guidelines for appropriate selection among the four most commonly employed materials (e.g., autogenous parietal bone, silicone rubber, methylmethacrylate, and porous polyethylene) so that optimal results can be achieved. Clinical follow-up ranged from 6 to 91 months (mean 32 months). Every patient was analyzed clinically by ordinary scale method. The mean defect size was 134.8 cm2 in the silicone rubber, 36.5 cm2 in the methylmethacrylate, 17.4 cm2 in the autogenous bone graft and 7.3 cm2 in the porous polyethylene. The clinical assessment was excellent (mean, 29.3 points) in silicone rubber, excellent (mean, 28.6 points) in autogenous bone, excellent (mean, 26.8 points) in methylmethacrylate, and good (mean, 24.8 points) in polyethylene. To sum up, a large bony defect of congenital calvarial anomaly produced an excellent result using custom-made silicone implant. A relatively small bony defect with a scarred bed produced an excellent result using autogenous parietal bone grafting. Unexpected and medium-sized defect was reconstructed successfully through a simple procedure using methylmethacrylate. Porous Polyethylene was used at an incidental small defect because of its expensiveness.
Assuntos
Humanos , Cicatriz , Seguimentos , Metilmetacrilato , Osso Parietal , Polietileno , Elastômeros de Silicone , TransplantesRESUMO
No abstract available.