Mechanical properties of a thoracic spine mannequin with variable stiffness control*

Abstract

Objective To test the posterior-to-anterior stiffness (PAS) of a new thoracic spine training simulator under different conditions of “fixation.” Methods We constructed a thoracic spine model using plastic bones and ribs mounted in a wooden box, with skin and soft tissue simulated by layers of silicone and foam. The spine segment could be stiffened with tension applied to cords running through the vertebrae and ribs. We tested PAS at 2 tension levels using a custom-built device to apply repetitive loads at the T6 spinous process (SP) and over adjacent soft tissue (TP) while measuring load and displacement. Stiffness was the slope of the force-displacement curve from 55 to 75 N. Results Stiffness in the unconstrained (zero tension) condition over the SP averaged 11.98 N/mm and 6.72 N/mm over the TP. With tension applied, SP stiffness increased to 14.56 N/mm, and TP decreased to 6.15 N/mm. Conclusion Thoracic model compliance was similar to that reported for humans. The tension control system increased stiffness by 21.3% only over the SP. Stiffness over the TP was dominated by the lower stiffness of the thicker foam layer and did not change. The mannequin with these properties may be suitable for use in manual training of adjusting or PAS testing skills.

Development of a mannequin lab for clinical training in a chiropractic program

“…Owens et al reviewed the recent uses of mannequins in chiropractic education and pointed out the need for a life-like mannequin that has similar material properties to human spinal tissue. 10 Indeed, Passmore et al 11 used bicycle inner tubes inflated to varying intensities to show that practitioners modulate the force and speed of their manipulative thrusts based on perceptions of the resistance to deformation of the material into which thrusts are delivered. While the FSTT system includes a Human Analog Mannequin (HAM) along with the force-plate table, the developers tested only the soft foam covering over the thoracic section, not the compliance of the undercarriage.…”

“…These presentations described the fixation mechanisms and compliance testing of the lumbar and thoracic sections. 10,[13][14][15] The first full-spine and pelvis mannequin was produced by combining those parts along with a newly developed cervical section in June of 2019. It was named PAT, the Palpation and Adjustment Trainer.…”