Investigation of bone quality of the first and second sacral segments amongst trauma patients: concerns about iliosacral screw fixation

Abstract

BackgroundIliosacral screw fixation has become a common method for surgical stabilization of acute disruptions of the pelvic ring. Placement of iliosacral screws into the first sacral (S1) body is the preferred method of fixation, but size limitations and sacral dysmorphism may preclude S1 fixation. In these clinical situations, fixation into the second sacral (S2) body has been recommended. The objective of this study was to evaluate the bone quality of the S1 compared to S2 in the described “safe zone” of iliosacral screw fixation in trauma patients.Materials and methodsThe pelvic computed tomography scans of 25 consecutive trauma patients, ages 18–49, at a level 1 trauma center were prospectively analyzed. Hounsfield units, a standardized computed tomography attenuation coefficient, was utilized to measure regional cancellous bone mineral density of the S1 and S2. No change in the clinical protocol or treatment occurred as a consequence of inclusion in this study.ResultsA statically significant difference in bone quality was found when comparing the first and second sacral segment (p = 0.0001). Age, gender, or smoking status did not independently affect bone quality.ConclusionIn relatively young, otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment. This study highlights the need for future biomechanical studies to investigate whether this difference is clinically relevant. Due to the relative osteopenia in the second sacral segment, which may impact the quality of fixation, we feel this technique should be used with caution.Level of evidenceIII

Bone density of first and second segments of normal and dysmorphic sacra

“…A subgroup analysis showed similar results. These findings corroborate the earlier results by Salazar et al [20] in a study of 25 normal sacra in which S2 was 28.1% less dense. Further analysis of our results showed that density was highest in the anterior and lateral ROIs of S1.…”

“…A Hounsfield unit value for each sacral segment was then calculated adapting the methodology from Salazar et al [20]. For each sacral segment, four circular regions of interest (ROIs) were strategically placed utilizing the axial CT sections (Fig.…”

“…Computed tomography (CT) scan has attracted interest as a means of evaluating bone mineral density (BMD) from studies ordered for other diagnostic purposes. Recent studies have evaluated the application of this technique to the sacrum [19,20]. Zou et al compared CT-acquired Hounsfield unit (HU) values at S1 with validated gold-standard DEXA and CT at L1, establishing guidelines for the use of HU in the sacrum as a marker for osteoporosis [19].…”

“…Zou et al compared CT-acquired Hounsfield unit (HU) values at S1 with validated gold-standard DEXA and CT at L1, establishing guidelines for the use of HU in the sacrum as a marker for osteoporosis [19]. Salazar et al [20] studied otherwise healthy trauma patients showing relative osteopenia of S2 in comparison with S1, which may have implications for iliosacral screw fixation of pelvic ring injuries.…”

Opportunistic Computed Tomography and Spine Surgery: A Narrative Review

“…The authors compared trajectory-specific ROI analysis in L1-L5, again finding that the CBT ROIs were consistently denser via HU analysis than traditional pedicle tracts. 68 Salazar et al 69 performed a similar analysis of screw trajectories at S1 and S2 in 25 consecutive trauma patients. Their intent was to shed light on whether placing iliosacral screws through S1 versus S2 made any difference.…”