The effect of bone density measurement with computed tomography on lumbosacral fusion and orientation of the sacral screw

Abstract

Objective: Sacral screw loosening is a common complication after lumbosacral fusion surgery. This study aims to determine the locations where screw loosening may be less with the help of computed tomography (CT)-derived bone density measurements in Hounsfield units (HU) in patients undergoing posterior lumbosacral fusion and to examine the effects of determining the trajectory of sacral screw placement on fusion success. Materials and Methods:The files of patients who underwent lumbosacral posterior fusion for different indications in our clinic between September 2017 and November 2020 were retrospectively reviewed. The patients' admission complaints, neurological examination findings, diagnoses, pre-operative HU values, and intraoperative and post-operative complications were evaluated. Results:The data of 50 patients were analyzed in this study. The study group predominantly consisted of patients with spinal stenosis (n=23). There were differences between the HU values of the right and left vertebral facets and the corpus vertebra (p<0.001). The subgroup analyses revealed higher HU values in the corpus vertebra (213.5) than in the right (82.5) and left (80.5) vertebral facets (p<0.001 and p<0.001, respectively), with no difference between the right and left HU measurements (p>0.999). The comparison between genders showed no significant difference (p>0.05). The mean follow-up duration of the patients was 29.3±14.12 (range, 10-48) months. Conclusion:We are of the opinion that pre-operative CT-derived bone density in HU provides the prediction of normal, osteopenic, and osteoporotic sacral segments, thus preventing screw loosening, which paves the way for surgical failure.