Biomechanical Analysis and Mid-Term Clinical Outcomes of the Dynamic-Transitional Optima Hybrid Lumbar Device

Area of Science:

• Spine surgery
• Biomechanical analysis
• Degenerative spinal disease

Background:

• Static spinal fusion can lead to adjacent segment disease (ASD) due to increased load on adjacent segments.
• Dynamic stabilization systems, like the Dynesys system in a dynamic-transitional optima (DTO) hybrid configuration, are investigated to mitigate ASD.
• Understanding load-sharing properties of dynamic stabilizers is crucial for preventing junctional complications.

Purpose of the Study:

• To investigate the effectiveness of a DTO hybrid configuration using the Dynesys system in reducing ASD and improving clinical outcomes.
• To analyze the mechanical performance and intermediate-term clinical effects of the DTO hybrid lumbar device.
• To assess how load-sharing properties of Dynesys stabilizers impact junctional complications in patients with varying disc degeneration.

Main Methods:

• Combined biomechanical finite element (FE) analysis and experimental analysis were employed.
• A two-level DTO hybrid procedure (L4-L5 static fixation, L3-L4 dynamic stabilization) was performed on 31 patients with lumbar spinal stenosis (SS).
• Radiological assessments measured disc height, listhesis, and angular changes; FE analysis simulated mechanical responses under controlled conditions.

Main Results:

• The DTO hybrid device reduced stress and motion at the transition segment, with greater compensatory effects at cephalad segments.
• The Dynesys cord-spacer configuration enhanced dynamic function at L3-L4, increasing motion and reducing disc stress and facet contact forces.
• Optimal cord stiffness varied with disc degeneration; pedicle screw motion contributed to interface stress, influenced by degeneration.

Conclusions:

• Modulating cord pretension in DTO instrumentation effectively reduced screw-vertebra interface stress and adjacent facet joint stress.
• The modified DTO system demonstrated potential for reduced pedicle screw loosening, ASD, and revision rates.
• This dynamic stabilization approach appears biomechanically favorable and clinically effective for managing transitional degeneration over the mid-term.