Extension creep in the lumbar spine

Area of Science:

• Biomechanics
• Spinal Anatomy
• Gerontology

Background:

• Sustained loading can induce viscoelastic deformation (creep) in spinal tissues.
• Previous research has characterized flexion creep; extension creep is less understood.
• Understanding lumbar spine biomechanics is crucial for managing spinal disorders.

Purpose of the Study:

• To investigate the in vitro extension creep of the human lumbar spine.
• To analyze how age influences lumbar spine extension creep.
• To correlate viscoelastic tissue properties with creep behavior under sustained extension.

Main Methods:

• Postmortem lumbar spines (n=25) from males were subjected to simulated extension and flexion loads.
• Sagittal range of motion and extension creep were measured over 20 minutes at end-range extension.
• Data were analyzed across three age groups: young adults, middle-aged, and elderly.

Main Results:

• Extension creep behavior was comparable to previously reported flexion creep.
• Elderly lumbar spines exhibited a trend towards greater extension creep than younger groups.
• Analysis of variance indicated no statistically significant differences in creep between age groups.

Conclusions:

• The viscoelastic properties of spinal ligaments, joint capsules, and intervertebral discs contribute to lumbar spine extension creep.
• The zygapophyseal joints may limit extension, potentially mitigating age-related changes in creep behavior.
• In vivo, even short durations of sustained extension loading could lead to significant lumbar spine extension creep.