Backache is caused by trauma, inflammation or nerve injury. A pathophysiological change in nerve, muscles, ligament, and joint of spinal canal causes chronic backache.
Pathophysiology of Back Pain or Backache:
- Radicular Pain: Chronic pain caused by pinched nerve or irritation of the nerve at nerve root close to spinal cord or at foramina before its exit from the spinal canal.1 Radicular pain is associated with tingling, numbness or weakness. Pain, tingling and numbness are symptoms of sensory nerve injury called as radiculopathy. Sensory symptoms are associated with weakness if motor nerve is irritated or squeezed.
- Muscular Pain: Backache is also secondary to muscle spasm, muscle strains (pulled muscles) and tear in the back muscles. Backache is often observed in fibromyalgia and myofascial pain syndrome.2
- Facet (zygapophysial) Joint Pain: Facet joint pain is seen in older patients suffering with degenerative disk disease and in individuals following surgery or motor vehicle accident.
- Ligamentum Flavum Hypertrophy: This is observed after trauma, whiplash injury and surgery.
- Posterior Ramus Syndrome (PRS): Also recognized as Maigne syndrome or thoracolumbar junction syndrome. Cause of unexplained activation of the posterior ramus of thoracolumbar nerves is unknown.
- Referred Pain – Visceral pain from stomach, pancreas and kidney disease is often referred to lower back and mid back3:
- Pregnancy: Chronic low backache is a common complaint in second and third trimester.
- Spondylosis: Spondylosis occurs following thinning of the intervertebral discs because of loss of moisture and disc volume with age. Minor trauma under these circumstances causes inflammation and nerve root impingement, which can produce classic sciatica like pain without disc rupture.
- Metastatic Cancer: Metastasis of primary cancer of breast, lung, prostate, or colon is very often detected in the vertebral column. Tumor located on the spine may press against a nerve, resulting in radicular and back pain. Tumor may invade into facet joints and present symptoms like facet joint pain.4
- Spinal Stenosis: Narrowing of the spinal canal is called spinal stenosis and narrowing of foramina is called foraminal stenosis. Spinal stenosis eventually may cause spinal cord compression within the spinal canal. Spinal cord compression will result in symptoms of cauda equina syndrome.
- Foraminal Stenosis: Spinal foramen acts as a conduit to pass spinal nerves at each segment to distal organs. Foraminal are narrowed by protrusion of thick ligaments, facet joint hypertrophy, bony spurs and intervertebral disc herniation. Foraminal stenosis will squeeze the nerves causing pinched nerve symptoms.
- Spondylolisthesis: Also known as slipped disc or subluxation of the vertebrae.5 Anterior or posterior displacement will cause facet joint injury and dislocation as well as spinal stenosis.
- Degenerative Disc Disease: This is mostly observed in older patients. Thinning of discs causes foraminal stenosis and disc herniation.
- Disc Bulge and Herniation: Bulged disc is a result of protrusion of the jelly like central portion (nucleus pulposus) of the disc. Bulged disc pushes against a nerve root causing symptoms such as tingling, numbness and weakness in the dermatome of the injured nerve and group of muscles.
- Fracture of Vertebrae: Pain, numbness and weakness may be secondary to pinched nerve or spinal cord compression. Weakness, paralysis and autonomic dysfunction (bladder and bowel dysfunction) indicate spinal cord injury. Severe whiplash injury or fall can cause fracture and dislocation.
- Long-Term Steroids: Steroid treatment for long term will cause osteoporosis and osteoporosis may cause fracture of the vertebrae. Fractured vertebrae may lead to severe intractable chronic pain as described earlier.