Myths and truths about low back pain

General information

Low back pain, also known as lumbago, is pain located in the lower part of the spine. This segment groups the vertebrae between L1 and S1.

The spine is a complex biomechanical system formed by the union of vertebrae, discs, ligaments and muscles. Likewise, in the spine, or through it, runs the spinal cord which is part of the central nervous system from which nerves enter and exit that give sensory and motor information to all parts of the body. Thus, many structures may be involved in an episode of low back pain. In most cases, there is not one, but several structures involved in the origin and perpetuation of the pain, and that is why it is fundamental to find which one or which ones are not the foci of low back pain.

Myths and truths about the causes of low back pain

Myths:

Many people think that the cause of low back pain is a spinal deformity, or the presence of a herniated intervertebral disc, but the truth is that in most cases low back pain is much more complex and spinal deformities are not precisely the most frequent cause. On the other hand, disc problems, including herniations, are not necessarily the primary cause of pain in most cases, and a more complete evaluation of the painful phenomenon is necessary to take into account a greater number of elements. Some years ago a study was carried out, which grouped the results of several studies (meta-analysis) on the results of MRIs of asymptomatic individuals, that is, without pain, and it was shown that there may be significant problems in the lumbar spine in people who do not express pain. In this study it was possible to document the presence of herniated discs and other significant problems in the lumbar spine (distensions and protrusions of the discs) in people who otherwise did not have pain. Thus it was demonstrated that the presence of problems in the intervertebral discs does not necessarily imply the presence of pain. Similarly, it is common to see people complaining of low back pain who otherwise have no evidence of damage or disease significantly affecting the spine.

Truths:

Very often low back pain is caused by inflammation of small joints that contribute to the stability of the spine, known as apophyseal joints or lumbar facets. Most authors are of the opinion that inflammation and especially overloading of the apophyseal joints is the main cause of mechanical low back pain in adults. The apophyseal joints are the connections between the different vertebrae and are the ones that allow the mobility of the spine, allowing flexion, extension and rotation movements. These small joints are formed by a capsule, surrounded and reinforced by ligaments that provide resistance to the joint. The facet joints are located in the posterior part of the vertebrae, while the discs are located in the anterior part. The discs have a rather elastic behavior and allow mobility in different axes. The discs are the ones that allow the absorption of the axial weight of the spine. The facets on the other hand have a more mechanical behavior. The facet is protected by the joint capsule, whose nerve endings carry information about the position and load of the joint.

Sometimes the main back problems are inflammatory, due to osteoarthritis of the facet joints mentioned above, or due to the presence of a herniated intervertebral disc. Frequently, herniated discs can advance towards the spinal canal or even partially occlude the holes through which the spinal nerves enter and exit the spine and produce irritation of these nerves.

In the case of the lumbar segment, compression of these nerves can lead to an episode of sciatica, which is a rather neuropathic type of pain that commonly radiates along the path of the nerve or nerves in question into one or both legs. When low back pain is associated with an episode of sciatica, it is known as lumbo sciatica and management may include infiltration of potent anti-inflammatory drugs such as corticosteroids into the epidural space, or even, eventually, surgical intervention.

However, most of the time, low back pain is mechanical and segmental. That is, it behaves as a rather localized pain in the lumbar region radiating diffusely to the posterior pelvis or the root of the thighs. It is usually a dull, sustained, bar-shaped pain. It worsens with trunk extension or rotation. In these cases, the most common elements involved are the facet joints as mentioned above and with involvement of the muscles of the lumbar spine, such as the axial muscles of the spine, or larger, deeper muscles such as the quadratus lumborum or iliopsoas. Lumbar pain with muscle involvement is usually very postural and is accompanied by stiffness and clicking that people often perceive as if something has broken or slipped out of place. The muscle fasciae, which are connective tissue structures that surround the muscles, often become inflamed and produce these clicks when they rub against each other as we move or adopt certain postures. The treatment of muscle contracture associated with mechanical low back pain should always be part of the integral management of this type of pain and often involves the intervention of rehabilitators or physical therapists.

At other times, less frequently, severe low back pain may hide a bone injury due to fracture and crushing of vertebrae. The vertebrae may break or collapse due to trauma or posture. This type of pain is quite intense, often sudden, and rarely responsive to conservative treatment. Loss of bone density due to aging is the most frequent cause of vertebral fractures. These fractures often make pain chronic and hinder the process of improvement and recovery. Fragility fractures should be suspected in very old, debilitated people, with osteoporosis or with debilitating chronic diseases, especially respiratory diseases. Other times vertebral fractures should be suspected after falls, trauma and accidents. For the diagnosis of these injuries it is necessary to resort to special imaging tests such as magnetic resonance imaging or computed tomography. Vertebral fractures are not uncommon. However, they are more frequent in the middle segment of the spine such as the dorsal part.

Osteoarthritis and the degenerative process of aging causes the intervertebral discs to become dehydrated and may grow tall. One of the functions of these discs is to absorb the axial weight of the spine. The loss of disc height increases the load on the facet joints, which become inflamed (arthritis) and form bone spurs that often occupy the space for the nerve root openings. These spurs or osteophytes can compress the nerve roots adding sciatica-like affectations to mechanical low back pain. Osteoarthritis of the spinal joints causes pain and stiffness that tends to perpetuate over time.

A rupture of the annulus fibrosus or a herniated disc can cause low back pain. The disc has a tough covering (annulus fibrosus) and a soft, jelly-like interior. If a disc is repeatedly overloaded by the vertebrae above and below it (such as when a person bends forward, especially when lifting a heavy object), the outer layer can tear (rupture) and cause pain. The contents of the disc can migrate through the tear and bulge outward (herniate). This bulge can compress, irritate and even damage the adjacent spinal nerve root, causing more pain and symptoms felt in one or both legs. A ruptured or herniated disc affecting the nerves also causes sciatica. However, imaging studies such as magnetic resonance imaging (MRI) often show bulging discs in people who have no symptoms or problems, as mentioned above.

Another frequent problem, often of a degenerative nature, is the narrowing of the lumbar canal. The spinal canal, located in the center of the spinal column, is the channel through which the bundle of nerves that make up the spinal cord extends. Narrowing of this canal is a frequent cause of low back pain in older people. Although there may also be people who were born with a narrow spinal canal. In people with narrow spinal canal there is usually sciatica type pain and intermittent claudication with walking associated with low back pain.

Conclusions

In short, low back pain is a complex phenomenon in which there is often no single cause. There are people with a lot of pain and with relatively correct imaging tests. In the same way that there are people with severe problems in the vertebrae or in the discs, without these people having pain. Degenerative problems of the joints and vertebral discs associated with aging are certainly the most frequent cause of low back pain in the elderly.

At MIVI Salud we normally receive patients suffering from these types of pathologies. By studying each case, we can provide a specialized solution to each type of pain.

 

Dr. David Garcia

Doctor of the Pain Unit of Mivi Sant Cugat, Mivi Sabadell and Mivi Lleida.