P40. Teriparatide treatment improves bone quality in the vertebral body out of proportion to the pedicles and lamina of the lumbosacral spine as measured by Hounsfield units

BACKGROUND CONTEXT Teriparatide treatment has been used to improve bone quality when considering spinal fusion surgery in patients with osteoporosis. This treatment has been shown to improve Hounsfield units (HU), a standardized measurement for radio density that can be obtained on CT scans, in lumbar vertebral bodies but its effect on other anatomic structures within the lumbosacral spine is unknown. STUDY DESIGN/SETTING Retrospective chart review. METHODS A retrospective chart review was performed from 1997 to 2018 across all campuses at our institution. We identified patients who had been treated with at least 6 months of Teriparatide with a lumbar or abdominal CT scan before and after therapy. HU were measured in the pedicles, lamina, and vertebral bodies from L1-S2. RESULTS Fifty-two patients (46 women, six men) were identified for analysis with an average age of 67 years who underwent an average of 20.9±6.5 months of Teriparatide therapy. Mean (± standard deviation) HU improvement in the vertebral bodies throughout the lumbosacral spine (L1-S2) was from 110±49 to 134±58 (p-value 0.029, 95% CI 2-44), a 22% improvement. HU in the pedicles increased from 222±98 to 255±102 (p-value 0.095, 95% CI -5 to 72), a 15% improvement. The lamina improved from 535±197 to 563±165 (p-value 0.44, 95% CI -43 to 98), a 5% improvement. CONCLUSIONS Teriparatide treatment improved bone quality as measured by Hounsfield units in the vertebral body, out of proportion to the improvement observed in the pedicles and lamina from L1-S2. This may indicate that improved screw fixation following Teriparatide therapy may be largely due to fixation within the vertebral body, but further biomechanical studies are warranted. FDA DEVICE/DRUG STATUS Unavailable from authors at time of publication.