Quantifying internal intervertebral disc strains to assess nucleus replacement device designs: a digital volume...

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Radiology

Background:

• Degenerative intervertebral disc (IVD) disease causes pain and biomechanical dysfunction.
• Nucleus replacement devices (NRDs) aim to restore IVD function, but clinical success is limited.
• Understanding NRD-tissue interactions is crucial for improving implant design and patient outcomes.

Purpose of the Study:

• To non-invasively quantify 3D strains in human cadaveric IVDs during nucleus replacement surgery.
• To evaluate the biomechanical effects of nucleus removal and subsequent NRD implantation.
• To assess the potential of NRDs to restore native IVD biomechanics.

Main Methods:

• Digital Volume Correlation (DVC) combined with high-field 9.4T MRI was used.
• Seven human cadaveric IVD specimens were axially compressed to 1 kN.
• Strains were measured in intact, post-nuclectomy, and post-NRD states.

Main Results:

• Nucleus removal significantly decreased disc height, which was restored by the NRD.
• Nuclectomy increased circumferential and shear strains in the annulus fibrosus.
• The NRD successfully restored these altered strain values to levels comparable to the intact state.

Conclusions:

• Nucleus replacement surgery can restore IVD height and normalize biomechanical strains.
• The DVC-MRI technique is a valuable tool for assessing NRD performance.
• These findings support nucleus replacement as a viable treatment for degenerate IVDs and guide future NRD design.