Quantifying the Risk of Spinal Injury in Motor Vehicle Collisions According to Ambulatory Status: A Prospective Analytical Study

Abstract

Background

The association between ambulation at the scene of a motor vehicle collision (MVC) and spinal injury has never been quantified.

Objective

To evaluate the association between ambulation and spinal injury in patients involved in a MVC.

Methods

Prospective analytical-observational cohort study. Inclusion: patients sustaining traumatic injury in a MVC. Exclusion: < 18 years old, pregnancy. Primary outcome: spinal injury defined as injury to the cervical, thoracic, or lumbar spinal cord, bones, or ligaments. Secondary outcome: Injury resulting in neurological deficit, need for surgery, or death. A generalized linear model was used to evaluate the association between outcome and predictor variables. Risk ratios [RR] were reported with a point estimate and 95% confidence interval (CI). A two-tailed alpha of < 0.05 was the threshold for statistical significance.

Results

There were 704 patients analyzed. Nonambulatory patients were 2.29 times more likely to sustain a spinal injury, compared to ambulatory patients (RR 2.29, 95% CI 1.34–3.91). Patients ≥ 65 years of age were 3.27 times more likely to sustain a spinal injury (RR 3.27, 95% CI 1.66–6.45). Patients with a Glasgow Coma Scale score ≤ 8 were 4.93 times more likely to sustain a spinal injury (RR 4.93, 95% CI 1.86–13.10).

Conclusion

In this prospective analytical-observational study evaluating the association between ambulatory status and spinal injury in patients involved in MVCs, we observed that those patients who were nonambulatory were more than two times as likely to have a spinal injury compared to those patients who were ambulatory at the scene.

Introduction

Spinal immobilization has historically been considered standard practice in the prehospital setting for patients sustaining traumatic injury and is one of the most frequently performed Emergency Medical Services (EMS) procedures, with over 5 million immobilizations performed annually 1, 2, 3. The rationale behind this procedure is to limit motion of an injured spine, thereby minimizing the potential to worsen an injury or the patient's neurologic outcome. This approach to spinal immobilization in the prehospital setting has been implemented as the standard of care for decades, with little scientific evidence justifying the practice 4, 5, 6. Although the benefits of spinal immobilization have been generally accepted on a theoretical and practical basis with limited data, there is growing evidence that this practice is not without risk, and is, in fact, harmful to some patients.

The risk of spinal immobilization for patients sustaining traumatic injury has been described in recent studies that have questioned the universal use of spinal immobilization backboards. In a 5-year retrospective study examining the effect of emergency immobilization on neurologic outcome in patients sustaining blunt traumatic spinal injuries, the authors found less neurologic disability in unimmobilized patients when compared to the universally immobilized patients (4). In penetrating trauma, spinal immobilization has been associated with twice the mortality compared to those patients not immobilized. The authors calculated the number needed to treat with spine immobilization to potentially benefit one patient at over 1030, and the number needed to harm with spine immobilization to potentially contribute to one death was 66 (7). Spinal immobilization has also been shown to contribute to pain, the development of pressure necrosis, and has been associated with restriction of normal respiration 8, 9, 10, 11. A Cochrane review evaluating the utility of spinal immobilization challenged the concept of universal spinal immobilization, stating that its effects on mortality, neurological injury, spinal stability, and adverse effects in trauma patients remains uncertain (12).

There is now agreement in the medical community that spinal immobilization is not needed for all patients sustaining traumatic injury. It is the position of the National Association of EMS Physicians and the American College of Surgeons Committee on Trauma that patients with penetrating trauma to the head, neck, or torso and no evidence of spinal injury should not be immobilized on a backboard (13). In light of this consensus, the relevant public health question now becomes what subgroup of the population sustaining traumatic injury indeed do need spinal immobilization? Increasing the diagnostic accuracy for which healthcare providers identify those high-risk patients is vital for preventing further injury for those patients who may benefit from spinal immobilization. Identifying those risk factors and exposures that increase the risk of spinal injury in patients sustaining traumatic injury is the first step in answering the ultimate question of who may potentially benefit from immobilization.

One component of the prehospital evaluation that may have implications for spinal injury is the ambulatory status of the patient at the scene. Although the position statement of the National Association of EMS Physicians and American College of Surgeons Committee on Trauma state that spinal precautions may be appropriate for this group, there is, to our knowledge, no literature that quantifies the incidence and relative risk of spinal injury according to ambulatory status in this population. The objective of our study is to evaluate the association between ambulatory status and spinal injury in patients involved in a motor vehicle collision; to quantify what has never been quantified in the literature. The quantification of the incidence and relative risk of spinal injury in this population has the potential to aid in the development of treatment recommendations and guidelines that maximize the ability to identify high-risk patients while minimizing spinal immobilization of those who do not need it.