In vivo loads on a vertebral body replacement during different lifting techniques

Area of Science:

• Biomechanics
• Occupational Health
• Spinal Loading

Background:

• Repetitive heavy lifting is a known risk factor for low back pain (LBP).
• Debate exists regarding whether squat lifting reduces spinal loads compared to stoop lifting.
• The impact of lateral lifting on spinal forces versus anterior lifting is also debated.

Purpose of the Study:

• To compare in vivo lumbar spinal loads between stoop lifting and squat lifting techniques.
• To investigate the effect of lifting a weight laterally versus anteriorly on spinal loads.

Main Methods:

• Instrumented vertebral body replacements (VBRs) were used to measure in vivo lumbar spine loads.
• 104 stoop and squat lifting tasks were performed by three patients.
• 26 lateral lifting tasks were also performed.
• Trunk inclination and knee bending were estimated from recorded images.

Main Results:

• A small difference (4%) in resultant spinal force was observed between stoop and squat lifting.
• Significant differences in knee bending (10° vs. 45°) and trunk inclination (52° vs. 39°) were noted.
• Lateral lifting resulted in 14% less implant force on average compared to anterior lifting.

Conclusions:

• Current in vivo biomechanical data do not support substantial differences in spinal loads between stoop and squat lifting.
• The anterior-posterior position of the lifted weight relative to the spine is a critical factor in spinal loading.
• Lateral lifting may be a safer lifting strategy to reduce spinal forces.