Measuring Hounsfield units (HUs) from computed tomography (CT) scans has recently been proposed as a tool for assessing vertebral bone quality, as it has been associated with bone mineral density, compressive strength, and fracture risk. Vertebral bone quality is believed to be an important determinant of outcome and complication rates following spine surgery and potentially influences success of interbody spinal fusion.
The purpose of this study was to investigate the association between HU on CT scans and fusion success in patients with lateral transpsoas surgery for lumbar interbody fusion (LIF).
The CT scans of 28 patients with a combined 52 levels of stand-alone LIF were evaluated at a minimum of 12 weeks postoperatively. Coronal and sagittal images were evaluated for evidence of fusion, and HU values were collected from axial images. HU measurements were also taken from vertebral bodies proximal to the construct to evaluate global bone quality.
Of the 52 LIF levels, 73% were assessed as fused and 27% were nonunited at the time of evaluation. The successful fusion levels had significantly higher HU measurements than the nonunion levels (203.3 vs. 139.8, p < 0.001). Patients with successful fusion constructs also had higher global bone density when vertebral bodies proximal to the construct were compared (133.7 vs. 107.3, p < 0.05).
With the aging population and increasing prevalence of osteoporosis, preoperative assessment of bone quality prior to spinal fusion deserves special consideration. We found that a successful lumbar fusion was associated with patients with higher bone density, as assessed with HU, both globally and within the fusion construct, as compared to patients with CT evidence of nonunion.
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Conflict of Interest:
Joseph J. Schreiber, MD and Fadi Taher, MD have declared that they have no conflict of interest. Alexander P. Hughes, MD receives personal fees from NuVasive, outside the work. Federico P. Girardi, MD receives personal fees from DePuy Spine, LifeSpine, NuVasive, Ortho Development Corp., Centinel Spine, Healthpoint Capital, Paradigm Spine, Small Bone Innovations, Spinal Kinetics, LANX Spine, SpineArt, Wenzel Spine, LDR Spine, and Ethicon, outside the work.
All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 .
Informed consent was waived from all patients for being included in the study.
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Level of Evidence: Prognostic Study Level III: See Levels of Evidence for a complete description.
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Schreiber, J.J., Hughes, A.P., Taher, F. et al. An Association Can Be Found Between Hounsfield Units and Success of Lumbar Spine Fusion. HSS Jrnl 10, 25–29 (2014). https://doi.org/10.1007/s11420-013-9367-3
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