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Measurement of Cadaver Lumbar Spine Motion Segment Stiffness

Brown, Mark D. MD, PhD; Holmes, David C. MS; Heiner, Anneliese D. PhD

Biomechanics

Study Design. Prospective.

Objectives. To measure lumbar spine motion segment stiffness and relate it to the degree of disc degeneration.

Summary of Background Data. The association between the instability of the lumbar spine motion segment and disc degeneration remains unclear. The traditional method for determining motion segment instability at the time of decompressive surgery is a manual test performed by the surgeon. To quantify instability of the lumbar spine, a vertebrae distractor was developed in the authors’ laboratory to measure motion segment stiffness by applying a defined load at a constant rate.

Methods. Lumbar stiffness was measured by subjecting cadaver lumbar spine motion segments to a constant rate flexion–traction load and recording the magnitude of the resistance to distraction versus the range of motion. Disc degeneration was measured by pressure–volume discography and by grading of disc morphology.

Results. Motion segment stiffness decreased with the initial stages of disc degeneration and then increased with severe disc degeneration. This measure of motion segment stiffness correlated well with a manual stiffness measure.

Conclusions. The observed results follow an accepted hypothesis of motion segment instability associated with disc degeneration.

From the Department of Orthopaedics and Rehabilitation, University of Miami School of Medicine, Miami, Florida.

Acknowledgment date: May 8, 2001.

Acceptance date: November 7, 2001.

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

Corporate/industry and institutional funds were received to support this work. One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, e.g., royalties, stocks, stock options, decision-making position.

Address correspondence to

Mark D. Brown, MD, PhD

University of Miami School of Medicine

Department of Orthopaedics and Rehabilitation (R-2)

P.O. Box 016960

Miami, FL 33101

E-mail: mbrown@med.miami.edu

© 2002 Lippincott Williams & Wilkins, Inc.