A method to study lumbar spine response to axial compression during magnetic resonance imaging: technical note

Area of Science:

• Biomechanics
• Medical Imaging
• Spinal Physiology

Background:

• Standard lumbar MRI scans are performed with subjects in a relaxed supine position.
• Spinal stenosis symptoms can worsen with moderate spinal compression.
• Existing MRI loading devices lack calibrated load control and do not account for imaging artifacts like viscoelastic creep.

Purpose of the Study:

• To develop and validate an experimental methodology for directly studying the lumbar spine's response to controlled compression during MRI.
• To establish a reliable protocol for measuring lumbar load-response and estimating muscle force contribution.

Main Methods:

• Development of an MRI-compatible spine compression unit utilizing pneumatic elements for precise load application.
• Testing with young healthy males subjected to loads up to 140% body weight for 10 minutes.
• Estimation of muscle force contribution to spinal load using electromyography.

Main Results:

• The developed compression unit delivered loads with a standard deviation of +/- 29 N.
• Spinal viscoelastic creep stabilized by 6.5 minutes, allowing 3.5 minutes for image acquisition.
• Internal muscle forces were found to be negligible (135 N) during external compression, simplifying analysis.

Conclusions:

• The established lumbar loading and imaging protocol is feasible within time constraints imposed by viscoelastic creep and subject tolerance.
• This methodology enables direct measurement of acute lumbar mechanical responses under controlled loading conditions during MRI.