RADIOLOGICAL ASSESSMENT OF BONY UNION AFTER OCCIPITOCERVICAL FUSION

Abstract

Study design: Assessment of posterior occipitocervical fusions, based on the post-operative (postop) follow-up radiographic findings. Objectives: To investigate an objective radiological evaluation method of the occipitocervical stabilization and fusion. Summary of Background data: For evaluation of the union of the non-instrumented or instrumented stabilization and bony fusion of the occipitocervical segments, only a few studies have been performed by some previous authors. Material and Methods: Occipitocervical fusions were performed in 20 patients from 1995 to 2007. The patients underwent occipitocervical fusions with 4 different surgical methods; autogenous iliac bone grafts and wire fixation (seven cases), loop and sublaminar wire fixation (five cases), Cotrel–Dubousse (CD) occipitocervical rod (two cases), and contoured reconstruction plate and screw systems (six cases). The stability and established union of the fused segment and the instrument failure or loosening were evaluated with flexion/extension lateral radiograms. The stability was evaluated by alignment change in degrees and distances between a point of the occiput and cervical vertebrae on the sagittal plane radiograms, taken at postop three months ago. Angular motion over 2[Formula: see text] and 2[Formula: see text]mm of displacement on radiograms were defined to be unstable and/or ununited. When there was no such motion of the fused segment and the instrument breakage or loosening, the fused segment was judged stable and fused. Results: Diagnosis of nonunion was made in three out of seven patients who have undergone fusion with autogenous bone grafts with wire fixation. In the other patients, we were unable to determine the presence of a solid fusion mass at the fusion site, because of overlapping of the instrument and graft bones. In all rigidly instrumented cases, stability was obtained. Conclusion: The occipitocervical fusion segments were judged clinically to be stabilized rather than fused, if the flexion/extension radiographs, taken at postop three and six months, did not demonstrate motion at the fusion site.