The bending stiffness of the trunk

Area of Science:

• Biomechanics
• Human Physiology
• Spine Research

Background:

• Extensive research exists on isolated human spine biomechanics.
• Limited understanding of the relationship between isolated spine properties and whole trunk properties in vivo.

Purpose of the Study:

• To review existing literature on spine biomechanics.
• To experimentally determine the in vivo bending stiffness of the human trunk in flexion.
• To compare trunk stiffness to isolated spine stiffness.

Main Methods:

• Literature review on spine physical properties.
• In vivo experiments measuring trunk bending stiffness in flexion.
• 150 measurements on unanesthetized subjects and 150 on anesthetized subjects.

Main Results:

• The bending stiffness of the whole trunk in vivo is significantly greater than that of an isolated spine.
• Trunk bending stiffness in vivo was found to be approximately 10 times greater than the mean bending stiffness of an isolated spine.

Conclusions:

• The whole trunk exhibits substantially higher bending stiffness in vivo compared to an isolated spine.
• This finding has implications for understanding spinal injury mechanisms and developing spinal implants.