Biomechanical Evaluation of a Growth-Friendly Rod Construct

Area of Science:

• Biomechanical Engineering
• Orthopedic Surgery
• Pediatric Spine Deformity

Background:

• Distraction rods are used to stabilize the thorax and improve lung function in pediatric patients with spinal deformities.
• The optimal amount of stability provided by these rods and the thoracic cage's requirement for stability remain undetermined.

Purpose of the Study:

• To investigate the biomechanical effects of a specific growth-friendly unilateral distraction rod on thoracic spine stability.

Main Methods:

• Five human cadaveric thoracic spine specimens were tested for range of motion and stiffness in multiple planes before and after the application of a unilateral distraction rod.
• Motion, stiffness, and intervertebral disc pressure were measured using optical markers and pressure transducers.
• Statistical analysis involved paired t-tests to compare intact and construct states.

Main Results:

• The distraction rod construct increased stiffness in the T1-T4 segment during extension by 30%.
• It reduced the range of motion in the T8-T12 segment during flexion by 63%.
• A significant decrease of 24% in elastic zone stiffness was observed in the T8/T9 segment during axial rotation.

Conclusions:

• The tested distraction rod device did not induce substantial biomechanical changes in the thoracic spine.
• Achieving the desired therapeutic biomechanical alterations while avoiding adverse effects presents a significant clinical challenge.