Back pain is a wide subject to cover as it is a term that holds a wide spectrum of conditions within.
The life time prevalence of Lower back pain is approximately 80% (1). A study was done in the United States showed that Low back is second only to the common cold as the reason patients cite for seeking medical attention (2).
It ranges from acute muscle spasms to degenerative changes of the discs and spinal joints (facet joints). The belief that DISC problems are the only cause of back pain no longer exists. There are many structures that can give rise to pain in the back. Muscles, joint capsules, ligaments, nerves, sacroiliac joints and the posterior (back) third of the disc all contain pain sensitive structures that give rise to pain when stressed or compressed.
Location and Nature of pain, onset, duration of symptoms, aggravating and relieving factors and the physical examination correlated by imaging (if needed) help to determine which structure(s) is at fault.
Mechanical vs Non mechanical back pain:
Mechanical pain. can be simply described as the pain aggravated or relieved with movement. It can be described as intermittent pain. For example, pain gets less or more on changing position from sitting to standing or during walking. Mechanical back pain could be due to tight tissues (muscles or fascia) disc problem, sacroiliac joint dysfunction, facet joint impingement, spinal stenosis, spondylolysthesis and osteophytes.
- Disc Pathologies: When we Flex (bend forward) the disc deforms posteriorly (backwards) or Posterolaterally (backward and to one side), in extension (bending backwards) it deforms anteriorly (forward) and when we bend to the right it deforms to the left and vice versa.
When the disc creeps posteriorly (backwards – central) or posterolateral ( backwards and to the side) it compromises the nerve root of the compressed side. When it creeps posteriorly (centrally) it presses the spinal cord. If it creeps anteriorly it presses the Anterior Longtudinal Ligament which is less significant compared to the first two directions.
It is when the disc presses the nerve root (posterolateral prolapse \ protrusion) or the spinal cord ( central) radicular symptoms such as pain, tingling, numbness and weakness result. This condition is called Radiculopathy. In Radiculopathy symptoms travel down the distribution of the nerve. Pressure of a nerve root in the neck will result in symptoms radiating to the upper limb. Pressure of the nerve root in the lower back result in symptoms radiating to the lower limb
Disc problems are commonly seen in the Lumbar spine more in the lower lumbar (L4-L5-S1) region where most of the body weight is transferred to. It’s less commonly seen in the Cervical region and rarely occur in the Thoracic region.
Disc pathologies can be classified into 3 main groups:
- Disc protrusions: in this group the annulus fibrosus is intact and the nucleus pulposus is contained but it protrudes through the weakened wall of the annulus .
- Disc prolapse: in this group the annulus fibrosus exhibits radial or circumferential fissuring allowing the nucleus pulposes to escape into the vertebral canal. The exposure of pain sensitive structures in the spinal canal to the leaked nucleus will result in irritation of the affected structure(s).
- Disc Sequestration: it’s a progression to prolapsed disc in which it degenerates and the intervertebral space height is reduced.
- Spinal stenosis: is a condition that results from the narrowing of either the intervertebral foramen thus producing unilateral (one side) symptoms or narrowing of the vertebral (spinal) canal and thus compressing the spinal cord giving rise to pain , parasthesia ( tingling\numbness\burning) and/or weakness. Narrowing of the canal is the result of degenerative changes and/or to central disc protrusion. The result of this narrowing is symptoms (pain or parasthesia) that radiates to the lower limbs with walking. The only relieving movement in this condition is flexion. In flexion the canal widens thus decompresses the spinal cord. As a result of this patients present with a flexed (forward bended) posture and tight hip flexors. On examination their back will be limited in extension but other tests will fail to give positive results.
- Osteophytes: also called “bone spurs” are bony projections that results from degenerative changes of the vertebrae. These projections develop at the peripheral margins of the disc or facet joints. They might end up causing spinal stenosis or compressing the nerve root at its exit.
- Facet Joint Impingement: As a general rule these joints open with bending forward and close with bending backwards. When the body bends to the right, the right facet joint closes while the left facet joint opens. The opening and closing of these joints becomes more complex with combined or twisting movements of the back increasing the possibility for these joints to get impinged. They cause pain on movement and result in limited motion at the level of affected segment(s). pain is mainly felt with motion at certain angles. In acute cases it might disturb sleeping.
Several factors can result in failure of these joints to open or close which results in pain and limit the motion.Main causes of facet joint impingement:
- Degeneration of the facet joints with aging.
- Guarding muscle spasm.
- Poor mechanics of the facet articular surfaces.
- Sudden moves.
- Spondylolisthesis: It’s a condition that results when one vertebra slips on the one below. This can be a since birth defect or acquired. The stacked up formation of Facet joints form what is called “Pars Interarticularis”. Failure at any level results in the slippage of the vertebra(e).
generally speaking, pain is provoked with standing for a long time and with exercising and the lower back motion is limited and painful in extension (backward bending of the spine) and Pain is alleviated by sitting.
Non-Mechanical Back Pain.
- Inflammation – chemical pain. Compression of a nerve root, locked facet joint (facet joint impingement), strained muscle will include irritation of the involved tissues. This inflammation is part of the healing process which is triggered by the body in response to injury. Inflammatory pain is almost felt constantly and subsides once the inflammatory process ceases.
- Postural syndrome – Ischemic Pain. This kind of pain is triggered by assuming poor posture. When someone slouches for example, muscle groups which are responsible of maintaining
the curvature of the spine will lose their optimal length. Some of these muscles shorten while other muscles lengthen. In both cases the blood flow to these tissues is compromised and as a result no enough oxygen is delivered. This kind of pain is triggered when tissues are put under sustained stretch or under sustained shortening and is alleviated when these tissues are brought back to their optimal length and position.
- Neoplasm. It is not a common cause of back pain. Patient general condition differs, looks ill, loses weight and complains of night sweating and pain that is aggravated during night (nocturnal pain). Pain is constant and progressively worsen with time.
- Viscero-Somatic pain: it is the pain that originates from internal organs and is referred to the back mimicking pain that is caused by somatic ( from the musculoskeletal system) dysfunction.