Postoperative displacement of ceramic spacers implanted during double-door laminoplasty

Double-door laminoplasty is widely used to treat compressive cervical myelopathy. In the original procedure, bone block grafts from the iliac crest were used to keep the split spinous processes separated, but several donor-site problems led to the use of artificial hydroxyapatite spacers (HA) instead. Although there have been reports of migration of implanted HAs, its true incidence and the cause of the migration have never been elucidated. The subjects of this study were 86 patients with compressive myelopathy treated by double-door laminoplasty in whom a total of 278 HAs were fixed between opened laminae with sutures. Antero-posterior (A-P) HA displacement developed in 42% of the patients, and axial HA rotation was found in 38%. In addition, the opening angle of the laminae augmented with an HA significantly changed in 34%. HAs installed far from the dura and/or in a rotated position were susceptible to postoperative displacement. (author)