TITANIUM CAGES AND ALLOGRAFTS FOR ANTERIOR THORACOLUMBAR SPINE RECONSTRUCTION: CT ANALYSIS

Abstract

Purpose of the study: Titanium cases are used to achieve mechanical stable spinal reconstruction immediately after corpectomy. Bone grafts is often associated to ensure long-term success. Plain x-rays do not allow correct visualization of the graft within the cage, hindering evaluation of the fusion. The objectives of this study were to obtain a precise evaluation of the graft outcome within the cage using computed tomography (CT) and to search for factors affecting bone fusion.

Materials and methods: This was a retrospective analysis of a consecutive series of patients undergoing anterior reconstruction of the thoracolumbar spine with a titanium cage and a bone autograft. 3D CT reconstructions were obtained at least three months after reconstruction surgery. Three independent observers (two surgeons and a radiologist) analyzed the images. Standard CT criteria for graft fusion are not described in the literature for this type of arthrodesis so the criteria used were based on a descriptive analysis of the CT slices. A statistical analysis was then conducted to search for factors affecting fusion: epidemiological features, etiology, type of graft, size of the case, number of levels reconstructed, associated posterior arthrodesis. The regional angle was analyzed postoperatively and at last follow-up to determine how the sagittal correction was maintained.

Results: Twenty-eight cases were reviewed. Reconstructions had been performed for burst fractures, tumor resection, or deformed callus. CT analysis demonstrated three fusion zones to be examined: the upper, middle and lower part of the cases. Bony bridges were noted at the extremities in all cases. The middle part of the cage generally presented a heterogeneous image which was insufficient to confirm fusion. Loss of correction was not significant. No co-factors could be identified which influenced fusion.

Discussion and conclusion: Most of the cases reviewed did not present a continuous bony bridge from one end to the other of the cage yet the sagittal correction was satisfactory and persistent. The structure of the cages might be modified with a solid intermediary zone which could «spare» graft material.