It is important to understand the anatomical arrangement in our lumbar spine (low back) in order to understand how and where problems can occur. Only after this, can effective treatment be applied.
The lumbar spine is typically composed of 5 vertebrae. They are numbered as L1-L5 from the top to the bottom.
In each vertebra there is…
1. A vertebral body in the anterior (front) aspect
2. An intervertebral disc between the vertebral bodies (above and below)
4. Transverse and spinous processes
5. Facet joints
The vertebral bodies are secured by a thick layer of an anterior longitudinal ligament in the front and posterior longitudinal ligament in the back between the vertebral bodies and the spinal cord in the spinal foramen.
In the center of the intervertebral disc is the nucleus pulposus in which gel-like fluid is contained. Numerous rings of ligaments called annulus fibrosis surround this gel sac for protection. This structural arrangement makes it possible for the spine to have a variety of range of motions—flexion (bending forward), extension (bending backward), lateral flexion (side bending), rotation and the combination of some of these movements.
The spinal cord travels through the spinal foramen behind the posterior ligament vertically from the cervical spine to the sacrum behind the posterior ligament. There is also a nerve root that exits from each side of the spinal cord and travels behind each side of the intervertebral disc. These nerve roots from the lumbar spine collectively become a bundle called the sciatic nerve. In brief, the sciatic nerve is responsible for the motor and sensory functions of the lower extremities (legs).
The Movement Mechanism
When flexion—forward bending—occurs, pressure is applied in the anterior aspect of the vertebral bodies causing the fluid in the nucleus pulposus to move posteriorly, or toward the back. Examples of forward bending are numerous in our daily activities, such as reaching down and stretching forward. In addition, sustained forward bending positions (as in prolonged sitting) can produce the same, or more magnified, effect as the flexion movement itself. Read more about this in the article we recently published: Bending Forward: the Risks.
In the same principle, in extension—backward bending—force is applied in the posterior aspect of the intervertebral disc, causing fluid in the nucleus pulposus to travel anteriorly. The most common activity involving extension is walking. The same principle applies to lateral flexion as well. Read about the benefits of walking.
Herniated Disc is believed to be the most common cause of low back pain as well as neck pain. When forward bending movement occurs too excessively, too frequently, or is sustained for too long, the fluid in the nucleus pulposus is forced to travel posteriorly and remain there. When such force continues to be applied, or increased, then the fibers in the annulus fibrosis begin to tear and the nucleus pulposus begins to bulge out. While the posterior longitudinal ligament protects the spinal cord in the middle from being pressed by the posterior force of the disc, lesions usually occur in the posterolateral aspects, through which nerve roots travel.
Local pain can result from the inflammatory process and calcified deposit. Movements would also be affected or often obstructed. Neurological symptoms can be seen when a nerve root is involved. Sciatica is one form of neurological involvement. Typical neurological symptoms can be tingling, numbness, sharp pain, referred pain (pain in any patch of the leg), radiating pain (pain shooting down the leg) in any part of the lower extremities, gait (walking) abnormality and muscle weakness, such as foot drop.
Back Bending For Treatment
While forward bending creates force pushing the lumbar disc to bulge posterolaterally as mentioned, backward bending creates the opposite effect. In the case of a posterolateral bulging disc where the herniation is not too wide or too large, backward bending can help cause the fluid from the bulge to flow back centrally to the nucleus pulposus.
The position in which this is performed should be carefully and precisely monitored. For example, due to body weight, the force applied to the disc when back bending is much greater standing than lying prone (lying down on the abdomen). Applying force that is excessive or too soon can result in an adverse outcome. The opposite can also occur. If inadequate force is applied, minimal progress is seen and symptoms persist.
If the herniation is large or wide, then further assessment is needed to precisely reduce it in a different direction. Back bending would then not be advised as a reductive regimen. Applying the right amount of force at the right time with the right progression and precautions can cause soft tissue lesions to reduce and heal within 2 weeks.
Active patient involvement makes Mechanical Diagnosis and Therapy the most effective treatment available for low back pain.