An experimental study of chest compression during chiropractic manipulation of the thoracic spine using an anthropomorphic test device.

PURPOSE: Chiropractic manipulation of the thoracic spine may induce chest deformations in the anterior-posterior direction. Yet, few studies have examined the biomechanical response of the chest associated with these manipulations. Consequently, an experimental analysis was undertaken to quantify chest compressions resulting from chiropractic thoracic spine manipulations and to estimate amount of risk for injury.

METHODS

A 2-part study approach was used with a Hybrid III anthropomorphic test dummy. In part 1, the dummy was positioned prone on a chiropractic table and subjected to thoracic spine manipulation by 2 experienced doctors of chiropractic. Chest compressions were quantified in the anterior-posterior direction. Manipulation forces were self-selected, with "typical" and "maximum" efforts examined. In part 2, the dummy was positioned beneath a force-instrumented mechanical piston device. Using the piston, chest compressions were induced with magnitudes identical to those recorded during chiropractic manipulation as well as magnitudes sufficient to induce injury. In all trials, force measurements were recorded.

RESULTS

Thoracic manipulations incorporating the typical and maximum efforts by the chiropractors resulted in maximum chest compressions attaining 1.8% and 4.5% of total chest depth, respectively. According to previously developed correlations between chest compression and injury severity defined using the Abbreviated Injury Scale (AIS), maximum chest compression measured during this study was only 22.7% of the compression required for greater than 10% risk of an AIS 1 injury. Abbreviated Injury Scale 1 level injuries are graded as minor severity and correspond to sternum contusion or fracture of a single rib.

CONCLUSIONS

Results from this preliminary study showed that maximum chest compression during thoracic spine manipulation corresponded to minimal risk of AIS 1 level injuries.