[Histological investigation on hydroxyapatite ceramics as materials of artificial bone grafts in the cervical spine]

The purpose of this study is to understand the utility of the hydroxyapatite (HA) ceramics as artificial bone graft substances in the cervical spine.

Dense and porous HA were implanted into the vertebral body and intervertebral space of the adult dog cervical spine and the implanted cervical bones were removed 4, 8 and 24 weeks after implantation and examined by contact microradiography (CMR), and histological observations of the non-decalcified material stained with Van Gieson's and decalcified material stained with hematoxylin and eosin.

1. Sufficient formation of new bone with the bone marrow was recognized on the surface and in the pores of the porous HA being implanted to the cervical vertebra. 2. Dense HA was inadequate for the implantation into cervical areas because of its physical nature, such as glass-like smooth surface and the extreme hardness. 3. HA was not fit for usage in the intervertebral space of the cervical spine because of its total ineffectiveness in the functions such as the supporting heavy weight of the head and the mobility and its histologically poor activity of the new bone formation in the intervertebral space.