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Discogenic Back Pain

What is Discogenic Back Pain?

Discogenic pain is one of the most common causes of lower back pain. Intervertebral discs act as shock absorbers between the two spinal vertebrae. As people age, the intervertebral discs undergo wear and tear like the cartilages of joints. It is a natural process whose exact cause is unknown. As a result, the physical and chemical properties of discs change over time, decreasing spine stability and flexibility. The prominent symptom of these changes is lower back pain. However, not everyone with intervertebral disc degeneration has lower back pain—a phenomenon yet to be explained.

Clinically Relevant Anatomy

The intervertebral disc (IVD) is the principal joint between two vertebrae in the vertebral column.


Each IVD is composed of three structures:

  1. The nucleus pulposus (NP), a gelatinous inner part;
  2. The annulus fibrosus (AF), an outer ring of fibrous tissue that encloses the nucleus pulposus;
  3. Two endplates of hyaline cartilage. 

 

The endplates serve as an interface between the disc and the vertebrae, they cover the upper and lower level of the annulus fibrosus and the nucleus pulposus.
The cells in the outer region of the annulus fibrosus are fibroblast-like cells which are disposed parallel to the collagen fibers, while those in the inner annulus fibrosus are chondrocyte-like cells.

The nucleus pulposus is made from randomly arranged collagen fibers and radially organized elastin fibers surrounded in a highly hydrated aggrecan-containing gel. There are a few chondrocyte-like cells in the nucleus pulposus. 

The intervertebral disc is mechanically similar to a thick-walled fiber-reinforced pressure vessel absorbing strain energy and transferring loads down the spine. The outer annulus fibrosus provides structural stability as the vessel wall with collagen fibril families layered in concentric lamellae of diversified orientation (between 45° and 65° off spinal axis), it is primarily a tensile member.

The nucleus pulposus mainly consists of hydrophilic proteoglycans; which absorb water and pressurize the disc, it also distributes weight to the annulus fibrosus and vertebral endplates and conserves disc height.


The graded properties of the disc change with degeneration and this can be visualized morphologically, biochemically and mechanically. 

Discogenic pain is attributed to degenerative changes in the intervertebral disc due to ageing or trauma. The healthy disc of an adult has scattered nerves which are mainly restricted to the outer lamellae. Degenerated discs have nerves that go through deeper intradiscal structures till the inner third of the annulus and the nucleus. These nerves contain nociceptive neurotransmitters and initiate production of cytokines, provoking nociceptive information from within the disc. 

What happens in Lumbar Discogenic Pain?

The intervertebral discs have three parts: the inner nucleus pulposus, the outer annulus fibrosus, and there are end plates above and below. The inner part (nucleus pulposus) has no nerve supply. But the nerve supply of the outer third of the annulus fibrosus makes it susceptible to pain upon any damage to it. Due to the process of degeneration, cracks appear in the outer part. The gelatinous material of the nucleus pulposus enters these cracks and irritates the nerve supply. The degenerating disc also releases many pain-causing substances in addition to growth factors that result in nerve growth into the disc. All these factors lead to the inflammation of the nerves and cause pain in the lower back.

What are the causes of Discogenic Back Pain?

Many factors increase the risk of getting this condition, such as:

  • Sitting positions and vibratory forces
  • Bending for excessive periods
  • Physical activities that increase stress on the discs
  • Being a male
  • Tobacco smoking
  • Obesity
  • Genetics and family history

 

 

What are the symptoms of Lumbar Discogenic Pain?

As the name suggests, the pain is felt in the lower back (lumbar area). Everybody experiences back pain differently. The general characteristics of lumbar discogenic pain include:

  • Acute or chronic low back pain
  • Pain increases with activities that increase pressure on the discs, such as sitting, bending, twisting, lifting, coughing, and sneezing.
  • Patient suffers from pain goes away by changing position or walking.
  • Pain does not radiate into the buttocks or leg (although it may radiate in chronic cases)

Other symptoms include tenderness, back weakness, muscle spasms, and the feeling of back instability. Some people also experience numbness and tingling sensation.

How to make a diagnosis of Lumbar Discogenic Pain?

Your doctor will make the diagnosis of lumbar discogenic back pain based on a combination of the following:

  • Signs and symptoms of lower back pain, weakness, numbness, etc
  • Medical history of your activities such as excessive driving, lifting heavy objects, bending for excessive periods, tobacco smoking, etc.
  • Physical examination to check for tenderness, numbness, and the range of back motion. The doctor will observe your gait and ask you to bend or twist your back to check for the range of back motion.
  • X-rays don’t help diagnose lumbar discogenic back pain but help rule out other spine-related conditions.
  • MRIs and CT discography can make a diagnosis. These tests can clearly show the degeneration of intervertebral discs and damage to other soft tissues.

What is the prognosis of Lumbar Discogenic Pain?

The prognosis of lumbar discogenic back pain is good with conservative treatments. Physical therapy, exercise, pain medications, and modifying activities relieve symptoms successfully. If pain and other symptoms remain for a longer duration (more than six months), surgery may be necessary.

What are the treatments of Lumbar Discogenic Pain?

There is no permanent cure for degenerating intervertebral discs. The goal of treatment is to manage symptoms and slow disease progression. Your doctor may recommend the following for this purpose:

  • Over-the-counter anti-inflammatory and pain medications such as ibuprofen to relieve pain initially.
  • Prescription pain medications such as muscle relaxants and opioids to relieve acute intense pain. Due to their addictiveness, these are used cautiously.
  • Rest and reducing or modifying activities that aggravate the pain
  • Applying heat and ice alternatively to the back every two or three hours when awake to relieve pain
  • Massage therapy and manual manipulation of the back to reduce tension in the back muscles and joints for pain relief
  • Intradiscal electrothermal therapy (IDET) – This is a minimally invasive treatment option between conservative nonoperative management and spinal surgery. Remaining clinical improvements can be realized in patients with mild disc degeneration. It may offer some pain relief for a small group of patients. This procedure appears to offer sufficiently symptom progress without additional complications. It also offers functionally significant relief in 50% of chronic discogenic low back pain patients. 
  • Radiofrequency annuloplasty – There is minimal evidence supporting the use of radiofrequency annuloplasty. 
  • Intradiscal biacuplasty (IDB) – The clinical benefits observed in the study of Kapural et al. are the result of non-placebo treatment effects given by IDB, but there is minimal evidence supporting the use of IDB in other studies. This should be recommended as a selection method for patients with chronic discogenic low back pain. 

Other treatments are:

  • Bi-annular pulsed radiofrequency disc method – The bi-annular pulsed radiofrequency disc method with consecutive P-RF, appears to be a safe, minimally invasive treatment option for patients with chronic discogenic low back pain. 
  • Intradiscal steroid injections – This method has not been proved to determine long-term benefits. 
  • Intradiscal radiofrequency thermocoagulation – No benefits have been found for the intradiscal radiofrequency thermocoagulation. 
  • Spinal fusion – If a spinal fusion surgery is performed, its aim is to stop the motion at a painful vertebral segment. There are many different approaches but they all involve the following process: firstly they add bone graft to a segment of the spine, secondly, they set up a biological response that causes the bone graft to grow between two vertebral elements. This creates a bone fusion which leads to one fixed bone replacing a mobile joint, so it will stop the motion at that segment. 
  • Ramus communicans block – A block in the ramus communicans is able to interrupt the passage of painful information from the discs to the central nervous system. 
  • Disc cell transplantation – Disc cell transplantation is in the experimental stage, it has the potential to become useful for the prevention and treatment of discogenic pain.

 

  • Physical therapy consisting of stretching exercises, strengthening exercises, and low-impact aerobic exercises is recommended. These are to relieve pressure on the back and build a healthy posture of the back. A physical therapist may help devise an individualized exercise plan.
  • Surgery is the last resort to relieve lower back pain. The standard surgery for relieving pain is lumbar spinal fusion, in which two spinal vertebrae are grafted together. The doctor may also recommend removing part of the disc or replacing the disc with an artificial one. But surgery has long list of side effects and is the last option.