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Trans-endplate nucleotomy increases deformation and creep response in axial loading
Wade Johannessen1, Jordan M Cloyd, Grace D O'Connell
1Department of Orthopaedic Surgery, McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA 19104-6081, USA.
Annals of Biomedical Engineering
|February 17, 2006
Summary
Removing nucleus pulposus material significantly impacts spinal disc mechanics, increasing deformation and altering motion. Functional disc evaluations must assess range of motion and creep behavior alongside stiffness.
Area of Science:
- Biomechanical Engineering
- Spinal Mechanics
- Regenerative Medicine
Background:
- Understanding the nucleus pulposus's mechanical role is vital for developing effective disc treatments.
- Previous studies on disc mechanics after nucleotomy may be confounded by concurrent annulus fibrosus disruption.
Purpose of the Study:
- To determine the mechanical contribution of the nucleus pulposus to axial load support.
- To investigate the effects of trans-endplate nucleotomy on spinal motion segment mechanics.
Main Methods:
- Sheep motion segments were divided into control, limited nucleotomy, and radical nucleotomy groups.
- Mechanical testing included compression-tension cycles, a 1-hour creep test, and a compressive ramp test.
- Axial deformations, neutral zone, range of motion, and creep behavior were analyzed.
Main Results:
- Nucleotomy increased axial deformations, widened the neutral zone, and expanded the range of motion.
- A graded response in elastic properties was observed relative to the amount of nucleus pulposus removed.
- Nucleus pulposus swelling was noted in the limited nucleotomy group but not the radical group.
Conclusions:
- Nucleus pulposus removal significantly alters spinal disc biomechanics, affecting stiffness, motion, and viscoelasticity.
- Functional assessments for nucleus pulposus replacements and disc implants should incorporate range of motion and creep measures.
- The extent of nucleus pulposus removal influences the mechanical response and swelling behavior of the disc.
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