Reconstruction of critical-sized
defects (CSDs) in bone shafts
remains a major challenge in orthopedics. Honeycomb (HC) scaffolds
are considered promising as their uniaxial channels bridge the amputation
stumps of bones and promote the ingrowth of bone and blood vessels
(BV) into the scaffolds. In this study, the ability of the HC scaffolds,
composed of the bone mineral or carbonate apatite (CAp), was evaluated
by reconstructing 10, 15, and 20 mm segmental defects in the rabbit
ulnar shaft. Radiographic and μ-computed tomography evaluations
showed that bony calluses were formed around the scaffolds at 4 weeks
post-surgery in all defects, whereas no callus bridged in the ulna
without scaffolds. At 12 weeks post-surgery, the scaffolds were connected
to the host bone in 10 and 15 mm defects, while a slight gap remained
between the scaffold and host bone in the 20 mm defect. New bone formation
and scaffold resorption progressed over 12 weeks. Histological evaluations
showed that mature bones (MB) and BV were already formed at the edges
of the scaffolds at 4 weeks post-surgery in 10, 15, and 20 mm defects.
In the central region of the scaffold, in the 10 mm defect, MB and
BV were formed at 4 weeks post-surgery. In the 15 mm defect, although
BV were formed, a few MB were formed. It is concluded that CAp HC
scaffolds have good potential value for the reconstruction of CSDs.