Adjacent level load transfer following vertebral augmentation in the cadaveric spine

Area of Science:

• Biomechanics
• Spinal Surgery
• Osteoporosis Research

Background:

• Osteoporotic vertebral compression fractures (VCFs) may stem from disease progression or increased adjacent level load transfer post-augmentation.
• Understanding load transfer is crucial for evaluating VCF treatment efficacy.

Purpose of the Study:

• To investigate whether augmenting osteoporotic vertebral compression fractures (VCFs) elevates load transfer to adjacent spinal levels.
• To compare biomechanical properties between normal and osteoporotic vertebral segments.

Main Methods:

• In vitro biomechanical testing of human cadaveric spinal segments (T3-T12).
• Segments were divided into normal and osteoporotic groups based on bone mineral density.
• Measurements included strain and centrum stress under intact, defect, and augmented VCF conditions.

Main Results:

• Osteoporotic segments showed reduced stiffness compared to normal segments.
• VCF augmentation partially restored compressive stiffness but did not alter adjacent level load transfer.
• Adjacent level loading was higher during subsequent VCFs, occurring at similar forces to initial VCFs.

Conclusions:

• Augmentation of VCFs normalizes adjacent level load transfer at physiological loads.
• Protection against adjacent VCFs diminishes as loads approach initial fracture levels.
• Subsequent VCFs are driven by extreme loading, not the augmentation procedure.