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Time-dependent changes in the lumbar spine's resistance to bending
1Comparative Orthopaedic Research Unit, Department of Anatomy, University of Bristol, Bristol, UK.
Clinical Biomechanics (Bristol, Avon)
|June 1, 1996
Summary
Loading speed and duration significantly impact back injury risk. Faster movements increase stress, while prolonged or repeated loading reduces the spine
Area of Science:
- Biomechanics
- Spinal Injury Research
- Occupational Health
Background:
- High bending stresses on the lumbar spine are linked to intervertebral disc and ligament injuries.
- Soft spinal tissues are viscoelastic, implying stress depends on loading rate and duration.
- Previous research has not fully quantified the impact of time-dependent factors on spinal bending stress.
Purpose of the Study:
- To investigate the influence of time-related factors on the risk of back injury.
- To quantify how loading rate and duration affect bending stress in the lumbar spine.
- To determine the relationship between movement speed, loading history, and spinal injury risk.
Main Methods:
- Mechanical testing of 45 cadaveric lumbar motion segments.
- Simulated in-vivo movements and postures using combined bending and compression.
- Measured bending moment at varying loading rates and after sustained/repeated loading.
Main Results:
- Rapid flexion increased peak bending moment by 10-15%.
- Repeated flexion over 5 minutes reduced peak bending moment by 17%.
- Sustained flexion or 2 hours of compression reduced peak bending moment by up to 42% and increased flexion range by 12%.
Conclusions:
- Time-dependent factors (loading rate, history) significantly influence lumbar spine injury risk.
- Spinal injury risk is not solely dependent on applied loads but also on temporal aspects.
- Findings highlight the importance of considering dynamic and historical loading in preventing back injuries.