Establishment of a rabbit's model for modified Capanna technique

Abstract

Massive bone allograft with an intramedullary vascularized fibula (Capanna technique) represents one of the most widely used methods for the reconstruction of massive bone defect. However, the mechanisms, healing process, and underlying influential factors were poorly understood due to the lack of suitable experimental animal models. Critical-sized defects (CSD) in bone were constructed in the proximal tibia of 24 rabbits and randomly divided into two groups. Allogeneic bone segments of the same size as CSDs were obtained from another 12 rabbits and then inactivated. In group Ⅰ, an ipsilateral pedicled vascularized fibula was dissociated and transferred into the intramedullary cavity of allograft to assemble a composite for CSD reconstruction (Capanna technique), while group Ⅱ received a reconstruction with allogeneic bone alone. Radiographic evaluation was performed every week after the operation to assess union status. All animals were sacrificed at 16th week, and the specimens were histologically analyzed. All animals survived without severe intraoperative complications. There was one rabbit (8.33%) in group Ⅰ developed a postoperative infection and died, while three rabbits (25%) had postoperative complications in group Ⅱ (two died of infection and one died of internal fixation fracture). Radiographically, the mean time to union at the allograft-host junction in group Ⅰ was 12.8±1.80 weeks, significantly shorter than in group II (>15.18±1.12 weeks; p<0.001). The grade of graft union of group Ⅰ was significantly higher than that of group Ⅱ both at 8th and 16th week (8th week: p=0.035; 16th week: p=0.033). Fully bone union at the junctions was histologically confirmed in all specimens in group Ⅰ and 66.67% (8/12) in group Ⅱ. Combined allograft and intramedullary vascularized fibula transfer in rabbit's tibia represent an ideal model that accurately simulates the Capanna technique for CSD reconstruction.