The Spine

One in four people suffer from back pain at any one time. The indirect costs alone are substantial — some 2% of the U.S. workforce is compensated for back injuries each year. Eighty-five percent of back pain is thought to be soft-tissue (muscular or ligamentous) mechanical in cause, the remaining 15% due to:

  • nerve root (1%) — e.g. herniated disc
  • facet joint — e.g. osteoarthritis
  • bone — e.g. osteomyelitis

However, much of the soft-tissue back pain (e.g. from muscle spasm) is often secondary to one of the above three causes. Nonetheless, be watchful for inflammatory back pain in younger patients as a clue to ankylosing spondylitis (AS): morning stiffness; improvement with exercise; alternating buttock pain; awakening during the second part of the night only. Furthermore, musculoskeletal pain usually gets better with rest while malignant pain or pain from infection often persist and are worse at night.

The ligaments and intervertebral discs account for the spine’s flexibility, particularly in the cervical and lumbar spine (accounting for the greater risk of spinal injury in these regions) but less so in the thoracic spine — were they promote greater stability. The spinal cord itself is most frequently injured between C5 and C6 level.

The main concern for the physician, when seeing a patient with new-onset back pain, is to differentiate the life-threatening condition from that of a benign cause: is there a serious underlying systemic disease responsible for the pain? Moreover, is there neurologic compromise present that would indicate spinal cord injury and necessitate further imaging and surgical consultation? While lumbar pain is more common, thoracic back pain is potentially more concerning.

Most herniated discs occur at L4/5 and L5/S1 level, resulting in sciatica — pain radiating down the leg beyond the knee. Test for any leg weakness. The absence of sciatica makes a clinically significant disc herniation unlikely.

Red Flags for a Serious Cause of Back Pain

  • immunocompromised patient — DM, HIV, steroids, transplant
  • fever
  • history of IVDU
  • history of recent infection
  • pain at rest or worse at night
  • neurologic deficit
  • elderly
  • history of malignancy
  • weight loss
  • pain > 6 weeks
  • trauma
  • history of osteoporosis
  • bowel or bladder disturbance — especially urinary retention ± overflow incontinence
  • bilateral leg symptoms
  • saddle anaesthesia
  • motor deficits, particularly if at multiple levels
  • vasculopathic risk factors

Serious Cause of Back Pain

  • spinal epidural abscess or haematoma
  • malignancy — 2/3 of patients with spinal epidural metastases will have a h/o malignancy (usually of breast, lung, prostate, kidney, or thyroid).
  • spinal fracture(s)
  • thoracic aortic dissection or ruptured aortic aneurysms
  • compressive mass
  • spinal column injury (with / without cord compression)
  • cauda equina syndrome

Of the 33 vertebrae of the human spine — 7 cervical, 12 thoracic, 5 lumbar, 5 (fused) sacral, and 1 coccygeal — the atlas (C1) and the axis (C2) are unique.

  1. Atlas (C1): a ring-like structure that articulates with the skull and responsible for 50% of the neck’s ability to flex and extend
  2. Axis (C2): the odontoid process is secured to the anterior portion of the atlas and allows rotation

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The vertebral bodies gradually increase in size as they descend.

The intervertebral discs have a spongy centre (nucleus pulposus) encased by dense fibrotic material (annulus fibrosus). Small tears in the latter may allow for prolapse of the former and possible impingement of the spinal nerves or the cord itself.

Lateral aspect of lumbar spine showing herniated nucleus pulposus (red). The spinal nerve, as shown here exiting its intervertebral (spinal) foramen can be readily compressed by a posterior herniation of disc material. [Image: flickr]

The cord is largest in the cervical region and the canal narrows significantly in the thoracic region, were a relatively smaller amount of pathological narrowing is required to cause a significant neuropathy (spinal nerve injury) or myelopathy (cord injury).

Examination

  1. Vitals
  2. CVS and Respiratory exam
  3. Musculoskeletal — Cervical, Thoracolumbar
  4. Neurological — strength, sensation, reflexes ± anal tone, perianal sensation

Imaging

Routine imaging is not recommended in patients with non-specific low back pain (LBP) [ACP, APS]. Rather, imaging should be considered whenever any of the following are present:

  • recent trauma
  • age < 18 or > 50
  • h/o cancer
  • pain at night
  • fever, immunocompromised, IVDU
  • symptoms greater than 4-6 weeks
  • neurologic complaints or incontinence
  • neurologic deficits on examination

References

Sherman SC. Simon’s Emergency Orthopaedics. 7th ed. Chicago: McGraw-Hill; 2015. 630 p.

Featured Image

Pixabay: https://pixabay.com/en/backpain-back-pain-back-pain-1944329/

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