Abstract
Background
Epidemiological studies have found associations between lifting, lifting and twisting
and twisting alone with increased incidence of disc herniation. This study investigated
the role of repeated dynamic axial torque/twist combined with repeated flexion on
the disc herniation mechanism.
Methods
Porcine cervical spines were tested in one of the following four testing protocols:
flexion–extension only; axial torque/twist only; flexion–extension followed by axial
torque/twist; or axial torque/twist followed by flexion–extension. Plane film radiographs
and computed tomography with contrast in the nucleus were obtained at regular intervals
during and following the mechanical testing process together with final dissection
to determine the disc injury patterns.
Findings
Axial torque/twist in combination with repetitive flexion extension motion, regardless
of order, encouraged radial delamination within the annulus (67.5% of specimens).
Alternatively, repetitive flexion motion alone encouraged posterior or posterolateral
nucleus tracking through the annulus. Axial torque/twist alone was unable to initiate
a disc herniation. Both X-ray images with contrast and computed tomography were not
good at detecting radial delamination observed during dissection.
Interpretation
The clinical relevance is that twisting may cause more radial delamination while repeated
flexion causes more posterior tracking of the nucleus giving guidance for both prevention
and rehabilitation decisions. In addition, X-ray images with contrast are not effective
at detecting the radial delamination which was exacerbated by combined loading in
flexion extension and axial torque/twist.
Keywords
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Article Info
Publication History
Published online: October 08, 2009
Accepted:
September 9,
2009
Received:
April 27,
2009
Identification
Copyright
© 2009 Elsevier Ltd. Published by Elsevier Inc. All rights reserved.
