Causes of Back Pain

The causes of back pain can be²:

Structural

• Mechanical or non-specific
• Facet joint arthritis or dysfunction
• Prolapsed intervertebral disc
• Annular tear of intervertebral disc
• Spondylolysis or spondylolisthesis
• Spinal stenosis

Neoplasm

Primary or secondary including multiple myeloma

Referred pain to spine from:

• Major viscera
• Retroperitoneal structures
• Aorta
• Hip

Infection

• Discitis
• Osteomyelitis
• Paraspinal abscess

Inflammation

• Spondyloarthropathies
• Sacroiliitis or sacroiliac dysfunction

Metabolic

• Osteoporotic vertebral collapse
• Paget’s disease
• Osteomalacea
• Hyperparathyroidism

The most important issue for emergency physicians is to be able to differentiate serious from less serious causes and, in particular, to be able to recognise cauda equina compression.

Cauda equina syndrome

Symptoms and signs of a cauda equina syndrome are:

• Acute low back pain (which may be superimposed on a history of chronic back problems)
• Radiation of pain to the legs (usually, but not always, bilateral)
• Lower limb weakness (frequently bilateral)
• Alteration of sacral and perineal sensation (usually, but not always, bilateral)
• Alteration of bladder and/or bowel habit leading to urinary retention and constipation

Not all patients will have all signs: the most sensitive are low back pain, perineal and sacral sensory loss and bladder disturbance.³ It is possible to have bladder dysfunction in the presence of intact anal tone. It may be missed if it is not considered and examined for and this is most likely to occur in the patient who walks into the department. Have a low threshold for requesting an MRI. A cauda equina syndrome (or spinal cord compression) is a surgical emergency that needs to be operated on within 24 hours after the onset of bladder symptoms. By the time the patient gets to the ED, bladder symptoms may have been present for many hours.

Non traumatic compression fractures

In women older than 50 years of age, the lifetime risk of vertebral fracture is estimated to be about one in three (including asymptomatic fractures). It may be very difficult (or even impossible) to date a fracture on X-ray especially as a previous fracture may have been asymptomatic; if there is no significant past history and the patient presents with acute back pain, it seems reasonable to assume the fracture is new / recent.⁴

Postmenopausal women with an initial fracture are at much greater risk of subsequent fractures.⁴

Other things that should be considered in patients with compression fractures but no history of trauma are metastases and multiple myeloma.

Spondylolisthesis

Spondylolisthesis is a forward slippage of one vertebra on another. The most common sites are a spondylolisthesis of L5 on S1 and L4 on L5.

The usual cause of the L5/S1 spondylolisthesis is a defect of the pars inter-articularis of L5 which allows slippage of the body of L5. This may be congenital or traumatic and tends to occur in young people.

Slippage of L4 on L5 is usually degenerative.

Spondylolisthesis may sometimes be seen as an incidental finding and so its presence in a patient with back pain does not necessarily mean that it is the cause of the pain. A CT may be helpful in determining the exact cause of the spondylolisthesis and its age.

Infection

Spinal infection, including tuberculosis (TB) is an uncommon cause of back pain but must be considered. Bone and joint TB accounts for about 1015% of non-respiratory tuberculous disease, and about half of this is in the spine. Spinal TB must, particularly, be considered in ethnic minority groups. The most common presenting symptom is back pain and there may be spinal tenderness and kyphosis. It may present with a paraspinal abscess as loin swelling or as a psoas abscess with spasm and hip flexion. Neurological symptoms can occur. Systemic symptoms such as weight loss and night sweats can occur but is not common in bony TB. There is no evidence to preferentially recommend CT or MR scanning for these patients.⁵

Malignancy

Patients with a history of malignancy may have non-specific back pain but metastasis should always be considered. The following symptoms and signs are suggestive of this:

• pain in the middle (thoracic) or upper (cervical) spine
• progressive lower (lumbar) spinal pain
• severe unremitting lower spinal pain
• spinal pain aggravated by straining (for example, at stool, or when coughing or sneezing)
• localised spinal tenderness
• nocturnal spinal pain preventing sleep

The investigation of choice is an MRI rather than plain X-rays.