Graded thoracolumbar spinal injuries: development of multidirectional instability

Area of Science:

• Biomechanics
• Spinal Injury Research
• Orthopedic Surgery

Background:

• Thoracolumbar spine injuries are severe, leading to disability and significant societal costs.
• Clinical instability following these injuries is often assessed using range of motion (ROM) and neutral zone (NZ) parameters.
• The relative sensitivity of ROM and NZ in detecting thoracolumbar spinal injuries requires further investigation.

Purpose of the Study:

• To compare the sensitivity and effectiveness of ROM and NZ in identifying and quantifying thoracolumbar spinal injuries.
• To establish the injury threshold and progression patterns using both ROM and NZ measurements.

Main Methods:

• A graded spinal trauma experiment was conducted on ten human thoracolumbar spine specimens (T11-L1).
• Specimens were subjected to high-speed incremental trauma to determine injury thresholds and progression.
• Range of motion (ROM) and neutral zone (NZ) were measured for flexion/extension, lateral bending, and axial rotation at various trauma levels.

Main Results:

• The injury threshold was identified at 84 J (84 Nm) for all motion types, with NZ proving more sensitive than ROM.
• At the injury threshold, NZ increased by 566% compared to only 94% for ROM.
• Beyond the injury threshold, NZ demonstrated significantly greater increases (up to 3000%) than ROM (up to 425%) with increasing trauma.

Conclusions:

• The neutral zone (NZ) is a more sensitive indicator of thoracolumbar spinal injury than the range of motion (ROM).
• Current clinical assessments using ROM from radiographs may underestimate the severity of spinal column injuries.
• NZ measurements offer a more comprehensive evaluation of spinal instability following trauma.