A newly designed vertebral replacement implant to reconstruct the thoracolumbar spine anteriorly

Calcium phosphate compounds are becoming of increasingly great importance in the field of biomaterials and, in particular, as bone substitutes. In this way donor-side morbidity can be avoided. A type A lesion of the vertebral body can be the reason of a neurological deficit, requiring a corpectomy by means of an anterior approach, tricortical bone grafting and internal stabilization to get a fusion over time. It is our aim to introduce in this study a newly designed vertebral replacement device, tested in an animal model, using domestic pigs. Two biomaterials, Cementek and Biobon were primarily macroscopically and microscopically evaluated, using a critically sized bone defect of a vertebral body and compared with autologous bone grafts. The final tests consisted of two groups of four animals. A corpectomy at the level of L4 was created and stabilized by means of the newly designed vertebral replacement implant. Autologous bone grafts were applied in one group of animals and Cementek in the other to fill the remaining space. Fusion was studied using anteroposterior and lateral radiographs, followed by a computer tomography. The biocompatibility of the biomaterials and autologous bone grafts were in order of: Cementek > autologous bone grafts > Biobon. In the final tests after a six months period, a fusion was diagnosed in four cases, two delayed unions, and two obvious non-unions. An analysis of the failures in this animal study can possibly clarify the shortcomings of this concept. Perhaps, subtle changes of the design combined with other synthetic bone substitutes can possibly improve the fusion rate in the near future.