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Measurement of In Vivo Intradiscal Pressure in Healthy Thoracic Intervertebral Discs

Polga, David J., BA*†; Beaubien, Brian P., BME*; Kallemeier, Patricia M., MD*‡; Schellhas, Kurt P., MD§; Lew, Willam D., MS*; Buttermann, Glenn R., MD; Wood, Kirkham B., MD

doi: 10.1097/01.BRS.0000127179.13271.78
Biomechanics

Study Design. In vivo pressures were measured in radiologically healthy middle and lower thoracic discs in 6 adult volunteers.

Objectives. To quantify and compare intradiscal pressures from the middle and lower thoracic spine during various body positions and maneuvers, and to investigate the potential variation of these pressures with orientation of the measurement transducer.

Summary of Background Data. In vivo intradiscal pressures have been reported for the lumbar spine; however, the authors are unaware of any studies presenting intradiscal pressures in the thoracic spine.

Methods. A specially constructed pressure-sensing needle was inserted into the nucleus pulposa, and pressures were recorded during a variety of body positions and maneuvers in middle and lower thoracic discs in 6 study participants. In three of the body positions, pressures were measured with the needle in both vertical and horizontal orientations to investigate whether the measured pressures were directionally dependent.

Results. Intradiscal pressure varied significantly with body position and maneuver, with pressures being greatest in positions where study participants held 10-kg weights in each hand. Disc level and orientation of the pressure needle did not significantly influence intradiscal pressure. In some body positions, thoracic intradiscal pressures were significantly different from previously reported pressures from the lumbar spine.

Conclusions. Thoracic intradiscal pressure was significantly influenced by body position and maneuver but not disc level. Intradiscal pressures are useful for gaining greater insight into the biomechanics of the thoracic spine.

In vivo pressures in the intervertebral discs of the middle and lower thoracic spine were measured in a variety of body positions and maneuvers in six healthy volunteers. Thoracic intradiscal pressure varied significantly with body position and maneuver but not disc level.

From the *Orthopaedic Biomechanics Laboratory, Minneapolis Medical Research Foundation, †University of Minnesota Medical School, and ‡Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN; §Center for Diagnostic Imaging, St. Louis Park, MN; and ¶Midwest Spine Institute, Stillwater, MN.

Acknowledgment date: February 13, 2003. First revision date: June 20, 2003. Acceptance date: August 26, 2003.

Supported by the Midwest Orthopaedic Research Foundation and grants from AO North America and the Minnesota Medical Foundation.

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

Foundation 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 to Brian P. Beaubien, BME, Orthopaedic Biomechanics Laboratory, Minneapolis Medical Research Foundation, 914 S. 8th Street, Minneapolis, MN 55404; e-mail: bbeaubien@mmrf.org.

© 2004 Lippincott Williams & Wilkins, Inc.