Comparison of prehospital cervical immobilization devices using video and electromyography

Previous evaluations of prehospital devices intended for spinal immobilization have focused on the device's ability to restrict motion only. This study defines six relevant criteria for evaluation of cervical immobilization device (CID) performance.

To suggest relevant criteria for evaluation and use available technology to improve measurements for performance testing of prehospital-care devices.

Six parameters (motion restriction, access, ease of application, environmental performance, radiolucency, and storage size) were used to evaluate three types of CIDs: Device A--a single-use corrugated board; Device B--a reusable foam-block CID; and Device C--hospital towels and adhesive tape. To test motion restriction, the most frequently compared parameters for immobilization devices, 20 volunteers were asked to move their heads and necks through a series of motions (flexion, extension, lateral bending, and rotation). Their movements were videotaped, still images of each movement were generated, and the degrees of deflection recorded from these still images. To ensure a consistent level of force, electromyography (EMG) of the sternoclydomastoid and extensor muscles was employed.

Data were produced for each parameter and presented for comparison. The use of video to determine deflection proved to be a useful and highly accurate (+/- 1o) method for measurement. The use of EMG technology enabled force to be controlled indirectly when the subjects used moderate levels of exertion. Overall, Devices A and C restricted motion better than Device B. Although Device C required the shortest time for application, it took the longest to prepare for application. The total time required for preparation and application of A and B essentially were equivalent, with A requiring no preparation time but taking the longest for application, and B having an intermediate interval for application. Device A allowed for the best examination of the head and neck. No differences were detected in performance in extreme environmental conditions or in radiolucency for cervical spine X-ray examinations. Device A consumed the smallest storage volume, B the greatest storage volume, and C an intermediate volume substantially greater than that required for A.

Device evaluation should include examination of all relevant performance parameters using the most accurate and meaningful methods possible.