Scintigraphic and Tomographic Evaluation of Biological Activities of Prefabricated Free and Vascularized Bone Allografts

Abstract

We performed an experimental study on rabbits to compare the biologic activities of free and vascularized cortical and corticocancellous solvent-dehydrated bone allografts by scintigraphy and three-dimensional computed tomography (CT). Twenty New Zealand white rabbits (2500-3000 g) were divided into 2 groups each consisting 10 animals. In group 1, solvent-dehydrated human cadaveric cranium allografts (corticocancellous bone) were used. The grafts were divided into 20 pieces, approximately 10 × 10 × 5 mm. On the right ears, grafts were placed on dissected vascular bundles. On their left ears, allografts were implanted into subcutaneous pockets without dissecting any vascular bundle. The same procedure was performed in group 2 with solvent-dehydrated human cadaveric fibula bone allografts (cortical bone). No infection or any animal death occurred during 12 months of observation. At the end of the 12th month, implanted bone allografts were evaluated by 3-phase bone scintigraphy to observe the circulation and viability of the grafts and three-dimensional CT scans to measure their dimensions. Radioactive uptake by scintigraphy of grafts placed on vascular bundle was higher than grafts placed in pockets. t-Test was calculated for region of interest of right ear (vascularized) to left ear rate (nonvascularized) according to graft type. Rate for corticocancellous bone graft was 1.187 ± 0.179 (P = 0.038) and cortical bone graft was 1.055 ± 0.052 (P = 0.038). There was correlation between region of interest generated from arm and neck regions and graft regions (P = 0.001). Regarding the dimension measurement made by three-dimensional CT, all the grafts grew whether they were on vascular bundle or not. Mann-Whitney test was used to determine whether differences between preoperative and postoperative volumes of grafts and growth of all grafts were significant (P = 0.007 for vascularized cortical bone and P = 0.005 for others). Kolmogorov-Smirnov test was performed to evaluate the distribution of growth rate. Vascularized medullar-cortical and nonvascularized medullar bone grafts expanded more than nonvascularized cortical bone (P = 0.001, P = 0.005, P = 0.001, respectively). Vascularized bone allograft combines the advantages of autogenous and allogenous grafts. Both scintigraphic and tomographic results overlapped that corticocancellous and cortical bones developed more on vascular bundle. Even though radioactive uptake was statistically higher in vascularized bone allografts, we determined that this small difference did not affect the overall late vascularity of the bone allografts. In conclusion, regardless their types or placement on vascular bundle, prefabricated bone allografts had similar metabolic function after 1 year of integration.