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Analysis of Preexistent Vertebral Rotation in the Normal Quadruped Spine

Kouwenhoven, Jan-Willem M., MD*; Vincken, Koen L., PhD; Bartels, Lambertus W., PhD; Meij, Björn P., DVM, PhD; Öner, F Cumhur, MD, PhD*; Castelein, René M., MD, PhD*

doi: 10.1097/01.brs.0000240209.85498.01

Study Design. In this CT study, vertebral rotation was analyzed in the transverse plane of the normal, nonscoliotic canine spine with a computer-based measurement method.

Objectives. To determine if a rotational pattern exists in the normal, nonscoliotic quadruped spine, similar to what is seen in humans.

Summary of Background Data. Idiopathic scoliosis does not occur in quadrupeds. In humans, the normal, nonscoliotic spine shows a preexistent pattern of vertebral rotation, which corresponds to the most prevalent curve types of idiopathic scoliosis. Since this rotational tendency has only been demonstrated in humans, it is not clear if it can be considered as a part of the pathogenesis of idiopathic scoliosis or as a normal anatomic feature.

Methods. CT scans of the thorax of 42 dogs without clinical or radiologic evidence of scoliosis were used to measure axial vertebral rotation from T1–T13 with a previously developed computer-based CT measurement method.

Results. The results of this study demonstrated a predominant rotation to the right of the upper, mid, and lower thoracic vertebrae of the normal canine spine. The mean vertebral rotation angles differed significantly from zero degrees rotation at level T1, from level T4–T7, and from T11–T13.

Conclusions. The normal spine of quadrupeds shows rotation of the thoracic vertebrae with a preferred direction to the right, similar to what is seen in humans. Since idiopathic scoliosis does not exist in quadrupeds, this preexistent rotation seems to be a physiologic process in normal spinal development, independent of the pathogenesis of scoliosis.

Vertebral rotation was analyzed in the transverse plane at level T1–T13 in the normal, nonscoliotic canine spine by using a previously developed CT measurement method. The results demonstrated a rotational tendency to the right, which corresponds to the preexistent rotational pattern in the normal human spine.

From the *Department of Orthopedics and the †Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands; and the ‡Department of Clinical Sciences of Companion Animals, Utrecht University, Utrecht, The Netherlands.

Acknowledgment date: March 8, 2006. Acceptance date: April 24, 2006.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Corporate/Industry 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.

This study was supported by AnnaFonds and Biomet.

Address correspondence and reprint requests to René M. Castelein, MD, PhD, Department of Orthopedics, G05.228, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands; E-mail:

© 2006 Lippincott Williams & Wilkins, Inc.