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Lumbar Axial Loading Device Alters Lumbar Sagittal Alignment Differently From Upright Standing Position: A Computed Tomography Study

Hioki, Akira MD*†; Miyamoto, Kei MD, PhD†‡; Sakai, Hiroshi MD, PhD*; Shimizu, Katsuji MD, DMSc†

doi: 10.1097/BRS.0b013e3181bb8188
Diagnostics

Study Design. A study was performed using an axial loading device in healthy young subjects.

Objective. To determine whether sagittal alignment during axial loading using a compression device can accurately simulate the standing posture.

Summary of Background Data. Axial compression devices are widely used for simulation of standing position during magnetic resonance imaging (MRI) or computed tomography (CT) scans. However, images taken during axial loading have not been compared with those obtained in a standing posture.

Methods. The study population comprised 14 asymptomatic healthy volunteers (7 men and 7 women: age 21–32, mean 27 years). Lumbar lateral radiograph films obtained in the standing posture (standing condition), lumbar CT images with axial loading using a DynaWell compression device (axial loading condition), and CT images without loading (control) were compared. Changes in spinal length, lumbar disc height, segmental lordotic angle, and total lumbar lordotic angle were compared among the conditions.

Results. Spinal length was significantly decreased in both the axial loading and standing conditions compared with controls. The magnitude of the changes was greater in the standing condition than in the axial loading condition. Segmental lordotic angle at L2/3 and L3/4 was significantly increased in both axial loading and standing conditions. However, disc lordotic angle at L5/S was significantly decreased in the axial loading condition, while the standing condition showed no significant change. Consequently, the pelvic angle showed a significant decrease in the axial loading condition.

Conclusion. The compression device simulates the lumbar segmental alignment change from supine to standing posture in L1/2, L2/3, L3/4, and L4/5. However, in L5/S, axial loading using the DynaWell altered lumbar segmental alignment with a kyphotic change, while no significant difference was observed in this level between standing and supine positions. Awareness of these phenomena are essential for accurate interpretation of imaging results.

Changes in lumbar alignment during axial loading were analyzed. The alignment changes on axial loading and standing were similar except disc lordotic angle at L5/S in which a significant decrease was observed during axial loading. Awareness of these phenomena are essential for accurate interpretation of imaging results.

From the *Department of Orthopaedic Surgery, Ibi Kousei Hospital, Gifu, Japan; †Department of Orthopaedic Surgery, Gifu University Graduate School of Medicine, Gifu, Japan; and ‡Department of Reconstructive Surgery for Spine, Bone, and Joint, Gifu University Graduate School of Medicine, Gifu, Japan.

Acknowledgment date: March 2, 2009. Revision date: July 12, 2009. Acceptance date: July 20, 2009.

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

Institutional funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address correspondence and reprints requests to Kei Miyamoto, MD, PhD, Department of Reconstructive Surgery for Spine, Bone, and Joint, Gifu University Graduate School of Medicine, 1–1 Yanagido Gifu 501–1194, Japan; E-mail: kei@bg8.so-net.ne.jp.

© 2010 Lippincott Williams & Wilkins, Inc.