SEATBELT SIGN; ITS CLINICAL SIGNIFICANCE...A REVIEW OF THE RECENT LITERATURE


Road traffic collisions (RTC) are a leading cause of preventable death in the U. S. ; killing more than 1.2 million people per year between the ages of 15 and 44 worldwide. There are more than 50 million non-fatal road traffic collisions every year, causing disabling injuries despite changes in legislation to improve seatbelt awareness, head restraint design, and vehicle crashworthiness (7).
The proper use of seatbelts reduces mortality in high speed RTC’s by 50-80% by preventing vehicle occupants from striking the interior of the vehicle. Seatbelts also prevent occupants from being ejected from the vehicle or rear seat occupants from becoming projectiles with a potential of injuring other vehicle occupants.
In high speed collisions, however, seatbelts have the potential to cause serious or fatal injury. The appearance of either cervical or lumbar seatbelt sign should alert the examining clinician to the possibility of spinal, neurovascular, or intra-abdominal injury (1). This literature review aims to illustrate the clinical significance of seatbelt sign. Although seen more commonly in the emergency room setting, family physicians, chiropractic, and orthopedic physicians will often discover it first in the outpatient setting. Until proven otherwise, a high index of suspicion for more serious injury must be maintained (3).


What Is Seatbelt Sign?


The seatbelt sign is characterized by patterned bruising on the chest or abdominal wall corresponding to the horizontal and diagonal positioning of the seatbelt on the occupant (1). This pattern can extend to the left or right side of the neck, depending on where the occupant is seated in the vehicle at the time of collision. Studies have demonstrated association between seatbelt sign and increased risk of vascular injuries to the neck, fractures of the cervical or lumbar spines, injuries to the abdominal organs or mesentery, vascular injuries of the abdomen, and injuries to the bladder, sternum, aorta, clavicle, and shoulder (1-3, 6).
Front seat passengers presenting with seatbelt sign are twice as likely to sustain intra-abdominal injuries (2). In one study, out of 117 patients injured in (mixed-type) road traffic collisions, (either front, side, or rear impact crashes) 12% had a seatbelt sign, 64% of which had abdominal injuries (2).
Seatbelt sign has a slightly different clinical significance when present in children due to increased potential for cervical spine fractures, spinal cord, or intra-abdominal vascular and hollow viscous injury. A lap belt placed improperly across the abdomen or across the shoulder / neck of a child has potential for serious or fatal injury. education and greater public awareness about the correct use of seatbelts and child restraint systems is necessary.


The Physical Examination


Cervical Seatbelt Sign: Careful physical examination of the patient with cervical seatbelt sign should include more than palpation of the posterior muscle groups and cervical range of motion.

  • Cranial nerves: A thorough cranial nerve examination takes only a few minutes and should be performed in the evaluation of every patient involved in a road traffic collision.
    1. olfactory nerve (CN1): smell; use peppermint or coffee bean
    2. optic nerve (CN2): pupillary constriction and accommodation, ophthalmologic exam
    3. oculomotor nerve (CN3): visual fields; superior, medial and inferior recti mm
    4. trochlear nerve (CN4): visual fields, superior oblique mm
    5. trigeminal nerve (CN5): mm of mastication, facial sensation (V1-V3 distributions)
    6. abducens nerve (CN6): visual fields, lateral rectus mm
    7. facial nerve (CN7): mm of facial expression, taste to anterior 2/3 of tongue
    8. vestibulocochlear nerve (CN8): hearing; tuning fork (Rinnes, Weber)
    9. glossopharyngeal nerve (CN9): taste to posterior 1/3 of tongue
    10. vagus nerve (CN10): sensory / motor to palate, pharynx, larynx, visceral motor fxn
    11. spinal accessory nerve (CN11): elevation of shoulders, sternocleidomastoid mm
    12. hypoglossal nerve (CN12): tongue protrusion / palate elevation

  • Cerebellar function: Cerebellar evaluation should include visual observation of gross and fine motor skills during the consultation / examination, as well as finger to finger / nose, heel to toe walk, and Rhomberg’s maneuver.

  • Deep Tendon and Pathologic Reflexes: The presence of pathologic reflexes; clonus, hyper-reflexia, or muscle spasticity could indicate spinal cord injury. Flaccidity, or gross motor weakness of an upper extremity should raise suspicion of possible disc herniation or brachial plexus injury.

  • Cervical Spine: Auscultation of the carotid arteries is recommended. Palpation of the anterior cervical spine for rigid unilateral muscle spasm or severe restrictions in range of motion, tracheal deviation, or dysphagia / hoarseness is also suggested. The presence of dizziness with transitioning or neck movement could indicate vascular injury, (vertebral or carotid arteries) upper cervical spine fracture, or dislocation.

  • Plain film X-ray: In addition to standard AP and lateral plain films of the cervical spine, an AP open mouth view is recommended in order to evaluate the odontoid process for fracture / dislocation. Flexion / extension views of the cervical spine as well as oblique views are useful in ruling out posterior arch fractures or spinal instability (injuries to the anterior or posterior longitudinal ligaments). Plain films of the chest and upper ribs may be indicated based on your patient’s presenting complaints.

  • MRI or CT: In my personal opinion, the presence of cervical seatbelt sign warrants imaging; closed high-field MRI of the cervical and upper thoracic spines. Vascular studies of the carotid and vertebral arteries may be indicated as well as MRI imaging of the brain.

Lumbar Seatbelt Sign

The presence of lumbar seatbelt sign should be evaluated equally as carefully as cervical seatbelt sign. Seatbelt syndrome is defined as a seatbelt sign associated with lumbar spine fracture and bowel perforation. This is caused by hyper-flexion of the lumbar spine around the lap belt in sudden deceleration leading to crushing of the intra-abdominal contents between the spine and seatbelt (1-3). Fixed portions of the bowel such as the jejunum and distal ileum are particularly susceptible to this type of injury.

  • Abdominal examination: Careful abdominal examination including aortic auscultation is recommended. Abdominal tenderness in combination with bruising over the lower abdomen warrants immediate referral for CT of the abdomen. Lower abdominal tenderness or changes in bladder function or hematuria require further evaluation / work-up.
  • Neurologic exam:
    -Motor strength: bilateral exam
      L4; tibialis anterior (ankle dorsi-flexion / inversion
      L5; peroneus longus (ankle dorsi-flexion / eversion)
      S1; extensor halluces longus (toe extension)

    -Deep tendon reflexes: bilateral exam
      L4; knee jerk
      S1; ankle jerk
  • -Pathologic reflexes: (upper motor neuron / CNS injury or pathology)
      Babinski, Clonus
  • Palpation, range of motion, and orthopedic maneuvers: Lumbar paraspinal muscles may spasm due to trauma. Root tension maneuvers such as the straight leg raise may elicit lower back pain with or without leg pain. The absence of leg pain does not rule out the possibility of disc herniation. In fact there is a higher incidence of disc herniation in patients between the ages of 25-45 years. Unilateral lower back pain worsened by transitioning from sit to stand or vice versa, is suggestive of sacroiliac injury. Lower back pain with or without radiation to the thighs is most suggestive of facet / zygapophyseal joint injury as the primary nociceptive structure in patients older than 55 years (9). Pain that is present with cough, strain, or sneeze is suggestive of possible internal disc disruption / disc herniation or facetogenic pain.
  • Co-morbidities: In either case of cervical or lumbar seatbelt sign, the presence of co-morbidities such as advanced age, osteoporosis, prior spine surgery, history of disc herniation, spinal stenosis, T2D, advanced cardiovascular disease; carotid artery or abdominal aortic aneurysm, or prior abdominal surgery must be factored into your clinical decision making regarding referral for imaging or consultation.

“Detection of active inflammation within and surrounding the facet joints (facet synovitis) is possible using a frequency selective fat saturation technique with or without contrast. It is not possible to reliably detect active inflamma-tion in the facets on routine MR imaging, without the use of fat suppression. It is recommended that MR imaging sequences with fat suppression be implemented in the routine protocol for MR imaging of the spine.
High field strength MRI units provide better spatial and contrast resolution and allow for more accurate interpretations than low field strength units; these findings may affect clinical treatment” (10).

Poor Outcome Is Associated With Whiplash Associated Disorders (WAD)


Accurate and credible assessment of long term outcome following WAD is based on initial presenting pain levels, psychological status of the patient following the accident, (including pain catastrophizing or presence of post-traumatic stress symptoms; hyper-arousal or startle reaction), and initial scores on the Neck Disability Index (NDI).
Previously considered factors such as neck range of motion, sensori-motor deficits, and collision dynamics (vehicle damage) have been determined as consistently UNRELIABLE throughout the peer reviewed research. Yet, auto insurers continue to argue outcome based on these factors. The use of such factors has no credibility.

Rear impact collisions produce HORIZONTAL SHEAR across vertebral endplates and facet joint capsules. Damage to these structures produces sustained abnormal mechanoreceptor signaling that is responsible for chronic pain. High-field MRI with fat-suppression technique is recommended in order to demonstrate injury to the facets and related anatomy: capsular ligaments and multifidus muscle attachments.Lewert   Seatbelt Sign Newsletter

References
1. Seatbelt sign and its significance. Amit Agrawal, Praveenkumar Ishwarappa. Journal of Family Medicine and Primary Care. 2013:Jul-Sep;2(3):288-290.
2. Seatbelts and road traffic collision injuries. Alaa K Abbas, Ashraf F Hefny.World Journal of Emergency Surgery. 2011;6:18.
3. Seatbelts: A double edged sword. P Raychaudhuri, N.K.Cheumg, C. Bendinelli.Case Reports in Pediatrics. 2012:326936.
4. Multivariable analysis of the relationship between pain referral patterns and the source of chronic low back pain. Ben L. Laplante, DO, Jessica M Ketchum, PhD, Thomas R. Saullo, MD, Michael J .DePalma MD.Pain Physician 2012;15:171-178.
5. The role of tissue damage in whiplash associated disorders. Michele Cutatolo, M.D., Nikolai Bogduk, M.D., et al. Spine. December 2012:S309-S315.
6. Late sequelae of whiplash injury with dissection of cervical arteries. Hauser V, Zangger P, et al. Eur Neurology 2010;64: 214-218.
7. The economic cost of road traffic crashes. Connelly L, Supangan R. Accid anals Prev. 2006; 38:1087-1093.
8. Course and prognostic factors for neck pain in whiplash associated disorders (WAD) results of the bone and joint decade 2000-2010 task force on neck pain and its associated disorders. Carroll L, Holme L, Hogg-Johnson S, Cote P, Haldeman S. Spine 2008; 33:583-592.
9. Structural etiology of chronic low back pain due to motor vehicle collision. DePalma M, Ketchum J, et al. Pain Med 2011 Nov12(11):1622-1627.
10. MR Imaging of facet synovitis and facet-related pain in the cervical and lumbar spine: The diagnostic value of fat-saturated magnetic resonance imaging. Czervionke, L, Fenton D, American Society of Spine Radiology, Blog Arch. Res. 2005, L, Fenton D, American Society of Spinev