An Association Can Be Found Between Hounsfield Units and Success of Lumbar Spine Fusion

HSS Journal: Volume 10, Issue 1

Joseph J. Schreiber, MD

Department of Orthopedic Surgery, Spine and Scoliosis Service, Hospital for Special Surgery
Weill Cornell Medical College

Alexander P. Hughes, MD

Assistant Attending Orthopedic Surgeon, Hospital for Special Surgery
Assistant Professor of Orthopaedic Surgery, Weill Cornell Medical College

Fadi Taher, MD

Department of Orthopedic Surgery, Spine and Scoliosis Service, Hospital for Special Surgery


Federico P. Girardi, MD

Associate Attending Orthopaedic Surgeon, Hospital for Special Surgery
Associate Professor of Orthopedics, Weill Cornell Medical College
Associate Scientist, Research Division, Hospital for Special Surgery

Abstract

Background

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.

Questions/Purposes

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).

Methods

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.

Results

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).

Conclusion

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.

Level of Evidence: Prognostic Study Level III: See Levels of Evidence for a complete description.

This article appears in HSS Journal: Volume 10, Issue 1.
View the full article at springerlink.com.

About the HSS Journal

HSS Journal, an academic peer-reviewed journal published three times a year, February, July and October. The Journal accepts and publishes peer reviewed articles from around the world that contribute to the advancement of the knowledge of musculoskeletal diseases and disorders.


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