Differences in bone mineral density of fixation points between lumbar cortical and traditional pedicle screws

Abstract Background Context The use of a novel lumbar pedicle cortical bone trajectory (CBT) screw has recently gained popularity, allowing for a minimally invasive approach and potentially improved screw purchase. However, to date, no studies have identified the ideal patient population to utilize this technology. Purpose This study reports the bone mineral density (BMD) using Hounsfield units (HUs) along a CBT screw pathway. Patients with a greater difference in density of bone in the lumbar vertebrae between the fixation points of the CBT and traditional pedicle screw may be optimal candidates to realize the advantages of this technique. Study Design/Setting A cross-sectional observational anatomic study was carried out. Patient Sample The sample comprised 180 randomly selected patients with lumbar computed tomography imaging from L1 to L5 spinal levels. Outcome Measures This study used computed tomography image-derived HUs as a metric for BMD. Methods A total of 180 patients without previous lumbar surgery with computed tomography imaging of the lumbar spine met the inclusion criteria. Patients were chosen randomly from an institutional database based on age (evenly distributed by decade of life) and gender. Hounsfield units were measured at the expected end fixation point for both a cortical (superior/posterior portion of the vertebral body) and traditional pedicle trajectory (mid-vertebral body). Results Hounsfield unit values measured at the end fixation point for the CBT screw were significantly greater than that of the traditional pedicle screw in all age groups. The relative difference in HU values significantly increased with each decade of age (p