Rebound devices such as trampolines are associated with catastrophic spinal cord injuries. Cadaveric studies have reported thresholds for injuries that can be applied to the case of failed acrobatics such as backward somersaults. However, it remains unclear whether falls on rebound surfaces should be expected to cause neurological injuries in the majority of cases or only in unfortunate exceptions. The purpose of the current study is to demonstrate the risk of injury associated with a failed backflip performed on a rebound device such as a trampoline or tumbling trampoline.
Backward somersault kinematic data was acquired using subjects fitted with a safety harness. This data was then applied to a testing rig designed to set a Hybrid III Anthropometric Test Dummy (ATD) in rotation and released at precise timing so as to reproduce failed backward somersaults. The ATD was instrumented to measure rotational rate, head acceleration as well as stresses in the lower cervical region.
The axial compression, shear force and flexion moment measured on average (SD) were respectively 1700 (470) N, 909 (667) N, and 360 (122) Nm while the threshold for bilateral facet joint dislocation (BFD) shown by previous cadaver studies showed a significantly lower threshold (p <0.001). Combined results have shown a likelihood of BFD for failed somersaults on tumbling trampolines ranging from 47 to 99%.
Failed backward somersaults causing BFD are also likely to cause neurological damage. Therefore, use of rebound devices requires the need for progressive skill achievement; supervision for beginners and the use of additional safety measures must be emphasized to prevent inverted vertical falls resulting in the specific combination of forces necessary to cause BFD.