Virginia Research Day 2021

A NOVEL INSTRUMENTATION PACKAGE TO QUANTIFY RIB BIOMECHANICS DURING OSTEOPATHIC MANIPULATION Stefan M. Duma, Andrew Kemper, P. Gunnar Brolinson

Results and Discussion For small displacements the rib strains varied between 1000 and 2000 microstrain and well below potential rib fracture values. Each rib responds with an individual strain profile depending on the type of thoracic loading. To measure the most extreme case – and beyond forces used for manipulation – extreme compressions were performed and the strain gages were able to measure exact rib fracture timing. These strains were much higher and varied by location. The strain values were higher for the female PMHS compared to the male PMHS (Figure 4).

Osteopathic manipulation of the thorax involves complex loading and subsequent displacements along individual ribs, sternum, and clavicles. The objective of this research was to develop a novel instrumentation package that can quantify the rib biomechanics during simulated manipulations. Materials and Methods Introduction For this study two human post-mortem human cadavers (PMHS) (one male, one female) were instrumented with 26 single axis strain gages on the ribs, sternum, and clavicle (Figures 1 and 2). The strain gages allow for direct measurement of local rib strain as well as fracture timing. The thorax of each PMHS was placed on a custom spine support bracket designed to support the thorax on either side of the spinous process, thereby allowing free motion at the costovertebral joints. In addition, the support bracket raised the thorax above the flat base plate, which could otherwise constrain the deformation and motion of the posterior region of the rib cage. The spine support bracket constructed of modular sections of varying height. This provided the ability to customize the bracket to the spinal curvature of a specific PMHS. Overall thoracic deflection of the thorax was measured using a string potentiometer at the sternum. The PMHS were then loaded using a custom table-top belt loading system that generated thoracic displacement through a belt system across the sternum (Figure 3).

Figure 2: Strain gages shown on a synthetic skeleton for illustration, 26 gages across the thorax.

String potentiometer

Accelerometer

Belt

Cadaver

Load cell plate

Conclusions This instrumentation package and these experiments illustrate that the rib biomechanics can be quantified during simulated osteopathic manipulation. Future experiments could utilize this technique to examine specific manipulations. Figure 4: Force versus chest compression indicating rib fractures for the female (above), male (below).

Load cell

Loading table

Load cell

MTS

Slack reducer

hydraulic

actuator

Figure 1: Strain gage placement on ribs (left) and latex covering to protect signal from moisture (right).

Figure 3: Thoracic loading system using hydraulically loaded belt system for compression control.

Presented at the VCOM Research Day, Blacksburg VA, February 26, 2021

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