A description of spinal fatigue strength.

Area of Science:

• Biomechanics
• Spinal Engineering
• Occupational Health

Background:

• Spinal fatigue failure understanding is vital for dynamic loading limits in occupational safety.
• Developing predictive models for spinal fatigue failure requires integrating experimental and published data.

Purpose of the Study:

• To develop a predictive model for spinal fatigue failure.
• To identify key parameters influencing spinal fatigue failure under cyclic loading.

Main Methods:

• Cyclic loading of 41 lumbar functional spinal units (FSUs) from cadavers under varying axial compression.
• Integration of published data from 70 thoracic and lumbar FSUs.
• Development of a fatigue model based on Wöhler analysis, incorporating endplate area, age, bone mineral density, and load parameters (Fmax, Fmin).

Main Results:

• A fatigue model combining Fmax, endplate area, and bone mineral density explained 61% of variation in fatigue failure (p<0.001).
• A model including Fmax, endplate area, and age explained only 28% of variation (p<0.001).
• Load-specific correction factors did not significantly improve prediction accuracy.

Conclusions:

• The study presents a basis for predicting specimen-specific lumbar spine fatigue failure.
• Endplate area and bone mineral density are key predictors of spinal fatigue failure.
• Accurate prediction requires considering specimen-specific properties and loading conditions.