288. Bone mineral density mapping of iliosacral region: the use of Hounsfield units to optimize trans-sacral screw trajectory

Abstract

BACKGROUND CONTEXT Trauma, degenerative and neuromuscular deformities often require placement of implants into sacrum for construct stability. In these scenarios, fixation to the ilium if often added. To date, multiple studies have validated the correlation between Hounsfield units (HU) as measured on computed tomography (CT) and bone mineral density (BMD) on dual-energy X-ray absorptiometry (DXA) to assess bone quality and fracture risk. PURPOSE We sought to map the BMD of the iliosacral region at the S1 and S2 levels using HU. STUDY DESIGN/SETTING Observational. METHODS HU measurements taken from the anterior and posterior ilium, sacral ala and sacral body using a best fit circle encompassing a maximal amount of cancellous bone of 100 pelvic CT scans. Following the collection of all data points, an analysis of variance (ANOVA) model was created to test the means and standard deviations of each anatomic region. RESULTS The highest mean BMD was found in the following locations (in descending order): S1 sacral body (279.72 HU, 95% CI, 261.75-297.69), S1 anterior ilium (254.45 HU, 95% CI, 236.64-272.27), S2 anterior ilium (229.88 HU, 95% CI, 211.39-248.36), and the S2 sacral body (191.58 HU, 95% CI, 173.31-209.85). Comparing the anterior ilium to the sacral ala, there was a higher BMD measurement at both the S1 level by 151.7 HU (p CONCLUSIONS The findings indicate that there is significantly higher BMD of the anterior ilium and sacral body when compared to the sacral ala at both the S1 and S2 levels. Given this, fixation through the lumbopelvic region should include implant placement within the anterior ilium and/or the sacral body to ensure fixation through densest cancellous bone. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.