Enhancing spinal bone anchor pull-out resistance with an L-shaped anchor

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Spinal Implants

Background:

• Spinal fusion surgery success relies heavily on spinal bone anchor fixation strength.
• Current anchors face limitations in pull-out resistance, potentially impacting surgical outcomes.

Purpose of the Study:

• To evaluate an innovative L-shaped spinal bone anchor designed for enhanced fixation.
• To assess the anchor's ability to create a macro-shape lock with the vertebral cortical bone layer.

Main Methods:

• Pull-out experiments were conducted on lumbar vertebra phantoms (L1-L5).
• The L-shaped anchor was tested in four perpendicular orientations (lateral, medial, superior, inferior).
• Pull-out force and anchor displacement were measured to determine maximal and initial pull-out forces.

Main Results:

• The L-shaped anchor demonstrated a maximal pull-out force of 123 N ± 25 N.
• Initial motion of the anchor required a force of 23 N ± 16 N.
• Maximum pull-out force was achieved when the anchor engaged the cortical bone layer.

Conclusions:

• The L-shaped spinal bone anchor with a macro-shape lock offers increased pull-out resistance.
• This fixation method shows potential for significantly enhancing spinal bone anchor stability.
• Combining this macro shape-lock with pedicle screws could further improve fixation strength in spinal fusion procedures.