Understanding Spinal Pain

Soft tissue trauma to a person’s spine stimulates the peripheral nerves located within the muscles and joints of the spine. These nerves are typical ‘A-Delta’ or ‘C’ fibres and they may respond to a stimulus such as tissue injury or direct pressure. At the peripheral level of the nervous system, tissue damage may result in the release of chemical mediators such as potassium, prostaglandin and bradykinin. These chemicals facilitate inflammation as part of the response to injury and they may induce swelling and engorgement. In addition to this, they stimulate peripheral nerve endings and can induce hypersensitivity. Thus areas of tissue that have not been damaged directly may become sensitised ( this is known as hyperalgesia and allodynia.)

How is Spinal Pain Caused?

Changes to the nerves (or neuroplasticity) may occur within the spinal cord after a peripheral injury. There may be an expansion in the size of the receptive field of the secondary neuron, which means that the nerve will now respond to a stimulus from adjacent areas. The threshold required to generate a nociceptive impulse (or pain signal) is reduced and in addition to this, the impulse produced is of greater size and lasts longer than before. There is also a lowering of pain thresholds so that a previously painless stimulus can now trigger neural impulses (pain signals) thus leading to the sensation of pain.

Injury and pain themselves can increase muscle tension around the spine and even trigger spasms of adjacent muscles. This is thought to be a primitive protective mechanism akin to the splinting of an injured body part. However, the tension may outlast the injury and actually exacerbate the symptoms. This may be associated with changes in posture and biomechanics that perpetuate the cycle of back pain.

The spine is a dynamic and sophisticated structure and physical activity is important to maintain optimal function even in the presence of back pain. If the patient rests too much following an injury this may worsen the condition by allowing loss of muscle strength. Specifically, stabilising muscles may be less effective in preventing joint wear and tear and may fatigue more easily and generate discomfort in their own right. Patients who remain active and strengthen the muscles of their back have a better outcome than those who rely on passive treatments.

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