Introduction

Low- and middle-income countries (LMICs) disproportionately bear the brunt of traumatic injury, accounting for over 90% of the world’s nearly 6 million annual injury-related deaths [1]. Mortality is increasing due to continued industrialization and motorization, now accounting for 32% more deaths than malaria, tuberculosis, and HIV/AIDS combined [1]. In 2019, the Global Burden of Disease Traumatic Brain Injury and Spinal Cord Injury Collaborators group found that traumatic spinal cord injury (TSCI) constitutes a considerable portion of this global injury burden, with more than 27 million cases in 2016, primarily caused by falls and road traffic injuries [2]. Morbidity and mortality from TSCI is also higher in LMICs due to inadequate prehospital care, limited inpatient specialty TSCI care, and a lack of post-TSCI rehabilitation [3]. Despite recent studies describing the deficit in training and resources to manage TSCI and need for alternative C-spine immobilization methods better suited to diverse LMIC environments [4], there are no large scale clinical trials to address use of a cheaper alternative for cervical-spine immobilization [5, 6].

While the disproportionate morbidity from TSCI in LMICs is multifactorial [3], a notable contributor to poor outcomes is a lack of prehospital emergency care [7]. Emergency medical services (EMS) are vital to provide immediate care and prevent secondary spinal trauma, which may occur in up to 25% of reported TSCI cases [8]. Yet, over half of the global population lives in areas without formal EMS [9], including 91% of the African population [10]. As a result, TSCI patients in LMICs rarely receive immediate spinal immobilization or are transported safely by trained personnel [11]. Most notably, cervical collar usage is particularly lacking in sub-Saharan Africa, even as compared to other LMICs [4], likely due to cost and resource limitations [12]. While it is known that well-organized EMS and prehospital care after injury are essential to improve TSCI outcomes [3, 13], the development of additional low-cost techniques for prehospital TSCI management are vital to address current gaps in TSCI care to improve outcomes in resource-limited African settings.

Prior studies have investigated the efficacy of traditional spinal immobilization techniques utilized in high-income settings [14,15,16]; however, there have been no trials of low-cost spinal immobilization alternatives focused on usage in resource-limited settings. Understanding the efficacy of low-cost alternatives that can address gaps in TSCI care in LMICs may expand scope of care and improve subsequent clinical outcomes. The present study evaluates the use of an alternative low-cost c-spine immobilization techniques.

Methods

Study design

Using a non-inferiority trial design, this study sought to evaluate alternative c-spine immobilization methods versus a c-collar, considered the gold standard [17]. Using thirty healthy young-adult volunteers with no history of spinal injury, we measured cervical range of motion (CROM) in six cardinal directions: flexion, extension, bidirectional lateral flexion, and bidirectional rotation in both seated and supine positions. A composite score generated from CROM across six cardinal directions with each factor weighted according to its proportional contribution to CROM was created to compare four immobilization methods and assess non-inferiority: cervical collar immobilization using a Laerdal collar, a folded towel technique, a pre-sized foam immobilizer made by OTC Professional Orthopedic, and no immobilization (control). Composite scores (CS) greater than 1 would surpass the non-inferiority margin and be deemed inferior.

Findings determined if the low-cost towel-based technique may serve as a non-inferior alternative means to immobilize the cervical spine in resource-limited settings where traditional c-collars are not available for prehospital use. This trial received ethical approval from the Washington University in St. Louis Institutional Review Board (IRB#: 202001119).

Study participants

Based on prior investigations of cervical-spine immobilization techniques [14, 15], we estimated a mean difference between cervical collar and towel groups to be ~10 degrees. As such, a sample size of n = 30 was determined to be sufficient for this study prior to commencement by using a power level of 0.8 and setting alpha to 0.05. Thirty healthy young-adult subjects with no history of spinal injury were recruited via snowball sampling through the Washington University Department of Biomedical Engineering. Participant medical records were screened prior to enrollment to ensure they did not meet any potentially confounding exclusion inclusion criteria, namely a past medical history of congenital spinal conditions or prior spinal trauma or a past spinal surgical history.

Novel immobilization technique

The immobilization technique investigated in this study required a full-sized bath towel. The following protocol was followed by an emergency medical technician trained in the technique for proper cervical-spine immobilization of each participant (Fig. 1):

  1. 1.

    A full-sized bath towel (80 cm × 150 cm) was folded in half twice vertically such that the length was unchanged.

  2. 2.

    The towel was wrapped around the posterior portion of the subject’s neck while each end of the towel was crossed around the chest such that the ends formed an “X” above the sternum.

  3. 3.

    Each end of the towel was tucked underneath the patient’s arms and held firmly by a first responder inferiorly to the axilla.

  4. 4.

    In the event in which the patient is unconscious, after crossing the wrapped towel over the sternum and passing both ends of the towel under the axillae, the towel ends are then tucked and held in place by the bodyweight of the torso while in the supine position.

Fig. 1: Towel immobilization protocol.
figure 1

In the supine position, the curvature of occipital bone of the skull naturally raises the cervical spine in an angle away from direct contact with the ground, thus creating a space posterior to the cervical column when the end of the wrapped towel may be passed.

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With this technique, the towel does not compromise the patient’s airway. Investigators ensured that traction was held constant on the towel to maintain proper c-spine immobilization. Participants were asked to immediately notify investigators if respirations became difficult while patients were simultaneously observed for accessory muscle use or sounds of upper airway obstruction or stridor as indicators of potential labored respiration, at which point the study would be stopped. Participants were also encouraged to adduct their arms to hold traction and keep the towel in place, especially in the supine position.

Data collection

Data was collected from a Performance Attainment Associates CROM device. Once fitted with each c-spine immobilization method, participants were seated in an upright position (Fig. 2) and instructed to move their neck in all six cardinal directions to the maximum possible extent.

Fig. 2: Sitting and Supine CROM experimental setup.
figure 2

Participant positioning for both seated and supine positions are shown along with CROM and immobilization device placement.

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The degree of movement was manually recorded from the CROM device after each movement when the participant indicated that they could not move their head further in the specified direction. Participants were then placed in a supine position and asked to repeat movements in four cardinal directions, which was again recorded using the CROM device and stored in Microsoft Excel (Microsoft Corporation, Redmond WA). Due to the reliance of universal inclinometers on gravity for measurements, lateral flexion could not be properly measured in the supine position. CROM data was analyzed in R (R Foundation for Statistical Computing, Vienna, Austria).

Data analysis

To define our non-inferiority margin, we utilized a fixed margin approach, preferred by regulatory authorities [18]. As a conservative estimate of the smallest effect size possible, M1 is defined either based on the pooled estimate or based on the limit of the CI that is the closest to the null effect. Given the fact that no placebo-controlled trials of the active comparator (c-collars) or meta-analyses of several placebo-controlled trials exist for cervical immobilization, we had no values upon which to base the definition of our non-inferiority margin. Therefore, the difference in spinal immobilization CROM measurements between the c-collar and the control (no immobilization) were compared in the six cardinal directions to determine M1. The median differences between c-collar and control states in each cardinal direction were calculated with between-group differences assessed using a Wilcoxon Rank-Sum Test with p < 0.05 deemed significant.

M2, also known as the “preserved fraction,” represents the largest clinically acceptable difference (degree of inferiority) of the test drug compared with the active control. In non-inferiority trials, the preserved fraction acts as a threshold to demonstrate non-inferiority [19]. The US Food and Drug Administration guidance for industry implicitly recommends to use a preserved fraction of 50% to determine M2 [18]. Factors influencing the choice of preserved fraction are the seriousness of the outcome measure (morbidity and mortality), the effect size, risk benefit‐profile and cost of the active comparator, the relative safety profiles of the test and the comparator, and whether it is believed that the effect of the active comparator has diminished over time (constancy assumption) [17, 20]. The higher, or more strict, the preserved fraction is, the more difficult it becomes to demonstrate non-inferiority. Preserved fractions of 50% are common practice in non-inferiority trials (cardiovascular, irreversible morbidity, and mortality outcomes), but stricter fractions have been used (90% M2 in antibiotics) [21,22,23,24]. With a higher percentage to be preserved (M1 = 70%, where M2 is 30% of M1), a stricter, more conservative non-inferiority margin is generated, meaning it is more difficult to conclude non-inferiority [20].

To calculate M2, clinical judgment informed by the morbidity and mortality associated with TSCI suggested the fraction of M1 that must be preserved by alternative spinal immobilization methods to remain non-inferior should be strict. Therefore, we determined 75% of M1 should be preserved to demonstrate non-inferiority, thus M2 = (1 − 0.75) × M1 = 0.25 × M1. Using CROM values, M2 values were then calculated in each of six cardinal directions of motion for the seated position and four cardinal directions of motion for the supine position using M1 values calculated above. Then, the median performance for both immobilization devices (towel and foam) measured by CROM values were subtracted from the corresponding c-collar values to compare relative performance. These new values were then divided by M2 to determine the percentage by which the difference would exceed the non-inferiority margin, with values >1 indicating the non-inferiority margin had been surpassed.

To then determine the overall performance of towel and foam immobilization devices in all CROM cardinal directions, we created a composite score, generated for both the seated and supine positions using the available six and four cardinal directions of CROM, respectively, with each factor weighted according to its proportional contribution to CROM (Equations 1 and 2). The composite score permits the comparison of immobilization methods and assessment of non-inferiority. Composite scores (CS) > 1 surpass the 25% non-inferiority margin and are deemed inferior.

Equation 1: Composite Score for Seated CROM measurements

$$CS\left( {seated} \right)= \,\left[ {\left( {1/8 \,\ast\, left\,lateral\,flexion} \right) \,+\, \left( {1/8 \,\ast\, {{{{{{{\mathrm{r}}}}}}}}ight\,lateral\,flexion} \right)} \right] \,+\, \left( {1/4 \,\ast\, extension} \right)\\ \, +\, \left( {1/4 \,\ast\, flexion} \right) \,+\, \left[ {\left( {1/8 \,\ast\, left\,rotation} \right) \,+\, \left( {1/8 \,\ast\, right\,rotation} \right)} \right]$$

Equation 2: Composite Score for Supine CROM measurements

$$CS\left( {{{{{{{{\mathrm{supine}}}}}}}}} \right)= \,\left( {1/3 \,\ast\, extension} \right) \,+\, \left( {1/3 \,\ast\, flexion} \right)\\ \, +\, \left[ {\left( {1/6 \,\ast\, left\,rotation \,+\, \left( {1/6 \,\ast\, right\,rotation} \right)} \right)} \right]$$

Equations 1, 2 were derived by consensus from senior authors. For Eq. 1, we proportionally divided each component equally to contribute 25% toward the overall score (flexion = 0.25, extension = 0.25, bilateral flexion = 0.25, and bilateral rotation = 0.25). Because lateral flexion and rotation are measured in two directions, both were further subdivided into left lateral flexion = 0.125, right lateral flexion = 0.125, left rotation = 0.125, and right rotation = 0.125), to generate Eq. 1. For Eq. 2, the same approach was utilized, by assigning each component an equal proportion toward the overall total: extension = 0.33, flexion = 0.33, bilateral rotation = 0.33. Bilateral rotation was further subdivided into left rotation = 0.1666 and right rotation = 0.1666, to generate Eq. 2.

Results

Participant demographics

Thirty healthy adults with a median age of 22 (IQR: 18, 24) participated in this study. Median participant height was 66.5 in (IQR: 64.25, 69.5), while median participant weight was 140 lbs (IQR: 124.25, 160) and median participant BMI was 22.26 (IQR: 20.28, 23.43). A total of 66.7% (n = 20) of the participants were female and 33.3% (n = 10) of the participants were male.

CROM measurement

Median values for each degree of rotation in each condition are shown in Table 1. The c-collar method yielded the greatest restriction of motion in all categories, followed in order by the towel, foam brace, and control (p < 0.01). Participants had a significantly higher range of motion when rotating right compared to left in all sitting conditions except when immobilized with a towel (p < 0.01). The towel immobilization protocol showed the greatest bilateral consistency across all conditions for both rotation and lateral flexion.

Table 1 Degrees of rotation from neutral.
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Composite scoring

As the composite score (CS) is generated from CROM across six cardinal directions with each factor weighted according to its proportional contribution to CROM and compares immobilization methods to assess non-inferiority, CS greater than 1 surpass the non-inferiority margin and suggest inferiority. Our findings demonstrated the seated CS of the folded towel technique and foam immobilization method were CSseated = 0.89 and CSseated = 2.35, respectively (Table 2). The supine composite scores of the towel and foam immobilization methods were determined to be CSsupine = 0.47 and CSsupine = 2.10, respectively (Table 3). Because the folded towel technique has composite scores less than 1 in both the supine and seated positions, our results suggest the folded towel technique is non-inferior, while the foam immobilization method is inferior because the composite score of CROM is greater than 1. Values in Tables 2, 3 represent CROM (measured in degrees) in each of the respective cardinal directions from initial neutral starting position between the four immobilization methods in seated (Table 2) and supine (Table 3) positions. These values measure the difference in degrees between the neutral starting position and the measured position at full range in each cardinal direction of CROM.

Table 2 Seated composite scoring.
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Table 3 Supine composite scoring.
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Discussion

Patients with cervical SCI have high propensity for respiratory compromise and thus are far less likely to survive compared to patients suffering from spinal cord injuries to the thoracic or lumbar regions [6, 25]. Given the increasing prevalence of mortality from SCI in medically underserved areas and the increasing risk for TSCI in low-income countries [26,27,28,29], innovative low-cost approaches are necessary for SCI management in the prehospital setting in LMICs. Our findings suggest the folded towel method is a low-cost alternative for immobilizing c-spine extension and rotation, but not flexion, when compared to cervical collars, while foam immobilization is inferior across all CROM measurements. In view of the inability of the folded towel to restrict flexion, we suggest that they be used in combination with spine boards for cervical immobilization. Further studies are needed to determine associated outcomes and whether non-inferior levels of c-spine immobilization in suspected TSCI patients may be achieved.

Previously, With current c-collars limited by the potential inadequate immobilization, restricted airway access and jugular vein compression, investigators are searching for alternative approaches to c-spine immobilization using various approaches to the evaluation of neck movement [30, 31]. A systematic review of methods for evaluating CROM in trauma settings found that biomechanical laboratory studies are being supplemented by new approaches using virtual reality, simulation, modern electromagnetic tracking technology, and miniature accelerometers, to more accurately investigate realistic, clinically-relevant trauma situations [30, 31]. Results of these studies have yielded findings suggesting that in healthy volunteers, soft and rigid c-collars provide similar restriction in CROM during 15 activities of daily living using a previously validated electrogoniometer device [32]. Further, CROM restriction using a rigid c-collar alone (versus c-collar and extrication device) in healthy volunteers reduces CROM in the sagittal plane during vehicle extrication, measured by 3-D infrared cameras calibrated around the vehicle to measure cervical-spine angle, angular speed and acceleration in the sagittal plane as well as surface wireless EMG electrodes to record superior trapezius, erector spinae and rectus abdominis muscle activity [33]. Spinal motion restriction (c-collar and securing to standard flat ambulance cot) has also been demonstrated to control cervical motion as well as traditional spinal immobilization (long spine board, head blocks, and c-collar) in a simulated prehospital ground transport setting by measuring cumulative integrated motion and peak range of motion [34]. C-collar use in the setting of back-boarding has further not been shown to reduce remaining movement of the c-spine in three subjects using a wireless human motion detector [35]. However, the use of these technologies in real life settings can be problematic and more research is needed, as few techniques for measuring CROM have been adapted to clinically-relevant scenarios [30, 31]. Our findings suggest that folded towels may provide adequate c-spine immobilization of extension and rotation compared to c-collars, which when used in combination with backboards may deliver affordable prehospital spinal cord injury management in resource-limited settings of LMICs where there exists a lack of access to cervical collars and thus limited cervical spinal immobilization.

In high-income countries, the majority of patients survive their first year after SCI. In fact, life expectancy has increased dramatically due to enhancements in medicine, prevention and treatment, including early acute management and long-term rehabilitation in high-income countries. However, there exists a large discrepancy in observed mortality between high-income and low-income countries, as cervical SCI patients are even less likely to survive the initial injury or hospitalization in resource-limited settings [6, 36, 37]. Patients with cervical, thoracic, and lumbar injuries have worse first-year survival rates than patients with similar injuries in high-income countries due to a lack of medical resources, healthcare access, and post-injury complications [38]. Among other social determinants of health, a lack of access, poverty, and lower literacy and education rates also contribute to a higher susceptibility to SCI [39]. In the prehospital setting of resource-limited areas, the ability to deliver timely acute care to SCI patients is lacking, as it is uncommon for an individual with an acute SCI to receive c-spine immobilization in the prehospital setting and be transported by trained personnel, which can further exacerbate neurological compromise [6]. Delays are quite common between the time of initial injury to the time of presentation for specialized care. A 10-year multicenter study in southeast Nigeria found c-spine to be the most commonly injured vertebral segment, which was associated with a higher mortality rate (16.7%) than those reported in high-income countries and attributed to a lack of EMS, critical care facilities, and greater incidence of high cervical injuries [40]. Meanwhile in the clinical setting of LMICs, an analysis of major postoperative complications for SCI has demonstrated that pressure ulcers, UTI, and septicemia are the most common complications and causes of premature death [39].

As described in prior studies, lay first responder programs serve as a highly cost-effective approach to address deficits in prehospital trauma care in LMICs [41,42,43,44,45]. The proposed towel immobilization is similarly frugal. This suggests alternative low-cost solutions may be employed by lay first responders providing prehospital care and transport, such as airway management and hemorrhage control. Alternative frugal solutions should continue to be investigated.

There were limitations to our study. Despite the homogenous nature of our sample with a young median age, our sample aligns with the main demographic disproportionately affected by trauma in LMICs, which are young people between the ages of 15 and 29 [46]. Though a sample size of thirty is relatively small, our sample was sufficient to demonstrate significance and is similar to sample sizes previously used in preliminary biomedical studies of efficacy of like techniques [14,15,16]. Additionally, we evaluated these immobilization techniques for short periods of time and did not measure their ability for use for larger durations of time intervals, though we do maintain a constancy assumption and do not expect a decay in efficacy over time given the mechanical nature of the intervention. The equations derived to determine CROM composite scores require further study for validation.

Conclusion

Limited cervical spinal immobilization and a lack of access to cervical collars in resource-limited settings of LMICs suggest alternative means of spinal immobilization are necessary to address morbidity related to TSCI disproportionately affecting LMICs. Our findings suggest folded towels may provide adequate c-spine immobilization of extension and rotation compared to c-collars. This low-cost method should be used in combination with backboards to deliver affordable and effective prehospital spinal cord injury management in resource-limited settings of LMICs.