The discs serve as strong cushions between the bones of the spine. They are complex and consist of a central nucleus of crabmeat consistency and surrounding circular fibers that are tough and arranged in crisscross patterns. The discs provide support, while at the same time allowing for the motion of the spine. Tears can form within the discs through the degenerative process or through injury. When these tears reach the outer circular (annular) fibers of the disc, where there are nerve endings and blood vessels, pain can arise. Disc pain tends to feel worse when there is increased pressure in the disc, such as with forward bending, sitting, coughing or sneezing, or lifting.
The treatment of disc-related pain can be challenging. Relative, but not complete, rest is only indicated for a short time (days) after an initial injury or flare-up. Some activity, such as walking or other person specific forms of exercise, can be quite good for the discs. Core exercises and attention to proper posture and activity technique can be helpful in symptom management. Some people respond to specific directional movements, which can be explored with a trained physical therapist.
Exciting biological treatments, such as the injection of stem cells, are being explored for the treatment of disc pain. When disc pain is especially severe and disabling, a spine fusion of the painful level can provide relief.
Chronic low back pain is most commonly caused by pain from the lumbar discs. Lumbar disc pain, otherwise known as discogenic pain, is the source of pain in approximately 40% of those with chronic low back pain, whereas the lumbar facet joints represent a prevalence of 10-30% and the sacroiliac joint 15-40% of cases of chronic low back pain. In some instances, the exact diagnosis cannot be determined or there are multiple sources of pain. Approximately 80% of people will have at least one episode of low back pain in their lifetime which leads to missed work and the seeking of medical care. When low back pain conditions become chronic, they can lead to a significant degree of chronic pain and disability, which often requires considerable utilization of health care and causes a decrease in quality of life. It is thus important to appropriately diagnose the source of low back pain, when possible, so that specific symptom management and treatment plans can be developed and carried out.
There are certain clinical clues which point to the possible diagnosis of lumbar discogenic pain. These include increased pain with sitting, forward bending, lifting, coughing, and activities which require forceful use of the arms and legs. These have in common the increase in pressure within the disc. Diagnostic (and therapeutic) spinal injections can be used to help determine the exact cause of back pain. Often, we start with injections that rule in or out the presence of facet or sacroiliac joint pain, if the clinical picture is not clear. The clinical picture, diagnostic imaging such as MRI and x-ray, and the use of these injections are helpful. The gold standard test for determining whether one or more discs are painful is lumbar discography. There are some who question the use or safety of this test, but when performed properly, the test is quite accurate and useful for treatment planning. Lumbar discography must be carried out using pressure manometry and at least one control level as per the International Spine Intervention Society (ISIS) Guidelines. An experienced practitioner, making use of these guidelines and narrow gauge needles, can provide the highest diagnostic yield and minimize the risks of the procedure.
Lumbar discography is carried out by first placing needles into the center of one or more discs. Contrast is then injected into the discs, while the pressure of each disc injection is measured. If a disc is found to have a tear or degenerative change, and is very sensitive to the injection of the contrast at low pressures, then it is likely that this is a source of pain. The degree of tearing, the pressure at which the pain arises, and the presence of normal control discs are all taken into consideration when making the diagnosis. The risks of infection or nerve injury are minimized by using sterile technique and careful navigation of the needle using fluoroscopic guidance. There is one published paper in which the author describes the possibility of the procedure itself causing an increased risk of disc injury and subsequent herniation, bulge or degeneration of the disc. There are others who question the validity of these findings and further research is needed to answer this question.
Discs develop internal tears and degenerative changes through a combination of mechanical stresses, cellular changes and biochemical changes. Internal tears can develop through repetitive stress injury with microscopic tears that extend (lengthen) gradually. Sudden bending, lifting or twisting injuries can occur, as well, extending the tear. When the tear involves the outer circular or annular fibers it reaches the nerve endings and blood vessels. This becomes painful, but also may induce an inflammatory response. The inflammatory response, if left unchecked, can result in progression of degenerative changes. Likewise, progressive degenerative changes can lead to a weakening of the internal structure of the disc, making it predisposed to mechanical trauma and tears. There are cells and chemical processes within the disc which can lead either to a healthy rebuilding status, known as anabolism, or a chemically unhealthy scenario where the balance is in favor of breaking down the disc, known as catabolism. There are known cellular reactions and proteins that promote healthy regrowth or anabolism, but also known chemicals that can be released which promote further degradation or catabolism within the disc.
The goal of regenerative therapies for discs, such as the use of platelet-rich plasma (PRP), fibrin sealant, or mesenchymal stem cells is to provide growth hormones, cells and proteins that influence (in the long run) the inflammatory status of the disc, and tip the disc back towards that of healthy regeneration (anabolism). There is ongoing research looking at the effect of injecting each of these into injured discs. These treatments show promise, although remain in experimental stages. Platelet-rich plasma (PRP) is the most practical and cost-efficient of the choices. This choice also makes good theoretical sense in terms of potentially returning the disc to a state of regeneration through its growth hormones and other healthy chemicals. It may have additional benefits such as possibly promoting disc cell activation and possibly even the reinforcement of sealing of disc tears. These are all theoretical actions of PRP, which may promote a return towards a healthier regenerative status within the disc.
The use of stem cells that are taken from a person and multiplied in a lab or supplied from sources other than the patient’s own stem cells are currently being studied. These involve companies with proprietary methods and are in clinical trial phases. These are heavily regulated by the FDA and not readily available outside of research studies at this time. The alternative is to obtain stem cells from individual patients. Stem cells can be obtained at the same time as the reintroduction (injection) of the stem cells into injured discs or other tissues. These can come from bone marrow aspirates or from adipose tissue (fatty tissue). These cells are then centrifuged (spun) to separate out the stem cells, which can then be injected into injured areas, including discs. This involves some local soreness at the harvest site and more expense than PRP. The cell counts vary with the various harvest techniques, although in general tend to be lower cell counts than with the commercial products. Since the cells come from the individual patient’s bodies and are not altered, there no need for FDA regulation and thus this option is more readily available.
The use of fibrin sealants or clotting chemicals from the blood is a promising option. A commercially derived product is currently being researched. There are other fibrin/thrombin clotting products on the market that are used for surgical indications that could be considered for intradiscal use at this time. This would be a reasonable option although can be costly.