THE EFFECTS OF PADDED SURFACES ON THE RISK FOR CERVICAL-SPINE INJURY

Study Design. This is an in vitro study comparing cervical spine injur ies produced in rigid head impacts and in padded head impacts. Objecti ves. To test the hypothesis that deformable impact surfaces pose a gre ater risk for cervical spine injury than rigid surfaces using a cadave r-based model that includes the effects of the head and torso masses. Summary of Background Data. It is widely assumed that energy-absorbing devices that protect the head from injury also reduce the risk for ne ck injury. However, this has not been demonstrated in any experimental or epidemiologic study. On the contrary, some studies have shown that padded surfaces have no effect on neck injury risk, and others have s uggested that they can increase risk. Methods. Experiments were perfor med on 18 cadaveric cervical spines to test 6 combinations of impact a ngle and impact surface padding. The impact surface was oriented at -1 5 degrees (posterior impact), 0 degrees (vertex impact), or +15 degree s (anterior impact). The impact surface was either a 3-mm sheet of lub ricated Teflon or 5 cm of polyurethane foam. Results. Impacts onto pad ded surfaces produced significantly larger neck impulses (P = 0.00023) and a significantly greater frequency of cervical spine injuries than rigid impacts (P = 0.0375). The impact angle was also correlated with injury risk(P < 0.00001). Conclusions. These experiments suggest that highly deformable, padded contact surfaces should be used carefully i n environments where there is the risk for cervical spine injury. The results also suggest that the orientation of the head, neck, and torso relative to the impact surface is of equal if not greater importance in neck injury risk.