After road traffic accidents and falls, sport accidents are the most frequent cause of traumatic spinal injuries (TSI) (1), with alpine winter sports representing about 20% of these (2–4) and the cervical spine being implicated in about 50% of cases (5, 6). Worldwide, the overall incidence of TSI is approximately 10.5 cases per 100 000 persons annually and around 37.3% of these have an associated spinal cord injury (SCI) (7, 8). Considering the potentially serious sequelae of TSI, historical pre-hospital and hospital guidelines recommend the application of full spinal immobilization using various orthotic devices (e.g. cervical collars (CC), sandbags, straps, backboards, splints, vacuum mattresses, etc.) during mobilizations and transfers of individuals with a suspected TSI (5, 9–14).
Recent data suggests the aim of pre-hospital care should be to achieve spinal motion restriction (SMR) rather than full immobilization (13). SMR objective is to reduce motion which may be achieved using manual in-line stabilization (MILS) without the addition of a cervical collar. Orthotic devices may be used as well but are not mandatory considering data now shows that the proposed benefits of full immobilization do not always outweigh the related risks (10, 15–19). Spinal immobilization with a CC may lead to serious complications such as pressure ulcers, airway difficulties, increased intracranial pressure, increased imaging and radiation exposure (14, 20–27); neurologic aggravations in ankylosing spondylitis (28, 29) and elderly patients (30, 31); and increased mortality in penetrating trauma patients (18, 32). Moreover, CCs installation requires precious time as well as winter clothing and helmet removal, inducing higher risks of CCs inappropriate use, victim cold exposure, and other hazardous events (33).
The prehospital benefits of cervical collar (CC) use for the application of SMR in wilderness settings remain thus strongly debated in clinical guidelines, which affect practices in the field. The Canadian ski patrol follows the National Institute for Health and Care Excellence (NICE) guidelines (5). According to these, ski patrollers should use a CC for rescues unless they can safely clear the C-spine before the victim extrication by assessing the risk factors for C-spine injuries. This is partly in line with the recommendations by the Wilderness Medical Society (17) which despite its main recommendation in favor of the cervical collar, mentions that in some situations "[the cervical collar] should not be considered necessary if adequate immobilization can be accomplished by other means" which include manual in-line stabilization (MILS) (17). Kornhall, D.K. et al. recently published prehospital Norwegian Guidelines emphasizing the limited evidence on CCs efficacy and supporting a selective approach to achieve timely rescues (10). The First Aid Task Force in their 2020 revised recommendations on cervical motion restriction and manual in-line stabilization suggests against the use of cervical collars by first aid providers (weak recommendation, very low-quality evidence) and concluded that there is insufficient evidence for or against manual in-line stabilization (34).
Current guidelines advising for or against the use of CC offer mostly weak recommendations based on low-quality evidence that is often not specific to the context of alpine rescue (14, 15, 18, 22, 32, 35–37). Thus, more data is needed and should be collected in real-life alpine skiing rescue situations to strengthen evidence and acknowledge geographic and meteorological conditions unique to their harsh environment.
Best practices studies on SMR application can be performed from an epidemiological perspective using observational design (cross-sectional surveys, cohort, or case-control studies), or in the form of biomechanical, pre-experimental, simulation-based studies with simulated patients, cadavers, or mannequins. Gathering accurate cervical spine motion (CSM) data during SMR application in a simulated patient, in a safe and convenient manner is challenging (38, 39). Various 3D motion capture technologies exist including optical motion capture, magnetic tracking systems, and inertial movement systems (40–43). Optical systems remain the gold standard but require a clear sightline to markers, making it technically difficult to use in situations with multiple rescuers crowding the victim. Magnetic systems operated under constrained volumes are not ultra-responsive to fast motion and might be affected by ferrous elements around the area (44, 45). Both optical and magnetic systems are almost inoperable in outside field conditions and are limited to a fixed experimental volume. Wearable Inertial measurement units (IMU) offer more flexibility to study SMR under field conditions (46–48), have good accuracy for short data recordings (45), but require a sensor to body calibration (IMUs’ record orientation in a global coordinate system that is not anatomically aligned with a specific joint coordinate system) which can affect their accuracy. In this study, we used a high-fidelity humanoid simulation mannequin with a 4-segment mechanical cervical spine instrumented with motion sensors to accurately capture CSM.
The aim of this study was to evaluate CSM variations occurring in alpine skiing rescues depending on the use or not of a cervical collar (CC versus MILS) during simulated extrications (EXs) and downhill evacuations (DEs) on real-life ski mountain terrains with this high-fidelity simulation mannequin.