Histological verification of bone bonding and ingrowth into porous hydroxyapatite spinous process spacer for cervical laminoplasty.

Three spinous processes of the cervical spine and implanted porous hydroxyapatite spacers were removed from a patient with a recurring intramedullary tumor at revisional laminectomy one year after spinous process splitting laminoplasty. Histological examination of undecalcified sections revealed direct bone bonding to the spacer at three of the six bone-hydroxyapatite interfaces. Bone ingrowth was observed up to 400 microns into the implant pores. Fibrous tissue was observed to intervene between the other three bone-hydroxyapatite interfaces. The suspected bone bonding with the spacer on CT scans before the revision was confirmed by the histological findings.