Back pain often arises from lifting, bending at the waist or trauma, but can also appear suddenly unprovoked. Millions of people suffer from back pain each year and can afflict both young and old. It is the leading cause of workdays missed.
Understanding the spine’s anatomy helps explain the causes of back pain. Made up of 24 segments called vertebrae, the spine is divided into 3 sections. The cervical spine (neck) is made up of the first 7 vertebrae. The thoratic spine (torso) consists of the next 12 vertebrae and have a rib attachment on each side. The lumbar spine (lower back) contains the last 5 vertebrae.
With exception of the first vertebra located directly underneath the skull, each vertebra consists of a vertebral body in the front and a pair of smaller facet joints in the back. Discs (tough ligaments) connect the vertebrae together (except for the first two) at the vertebral bodies. Approximately 80% of the body’s weight is born by the vertebral bodies when standing, and the other 20% is born by the fact joints (allowing controlled movement such as bending and rotating).
5 layers of muscle surround the spine. These are: the multifidi, rotators, erector spinae, iliocostalis and quadrates lumborum. Working together, these muscles move and support the spine.
The cause of an individual’s back pain can be from one or more of several sources. The following is a brief description of some of the more common causes:
Soft tissue structures (muscle fibers, tendons and/or ligaments) can tear if the loads they are carrying exceed their strength capacity. Inflammatory products are released if these soft tissue structures are injured, leading to swelling and pain.
Underneath cartilage, the surfaces of the facet joints are imbedded with nerve endings. If degenerative joint disease or trauma causes the cartilage to be worn down, irritation of the nerve endings can occur, causing pain.
Discs have both an outer layer and an inner layer. The outer layer is called the annulus. The inner layer is a jelly-like material called the nucleus pulposus. The nucleus can puncture through the annulus if the annulus fibers weaken. While this can occur over time without any specific trauma, this more often occurs due to some type of trauma, such as from a lifting incident. If a protrusion of the nucleus presses against a nerve root, radicular pain can occur, radiating down the leg. Muscle strength and sensation can be affected in severe cases.
The annulus consists of concentric rings of collagen. If a fissure develops between rings, an inflammatory reaction can develop. When this type of pain occurs, it is deep within the spine and is aggravated by certain movements, especially twisting at the waist.
The spinal cord is located in a canal formed in the space between the vertebral body and facet joints. This canal can be narrowed by arthritic changes causing bony projections on the vertebral body. The Spinal cord can be pinched by this narrowing, causing numbness, tingling, weakness, muscle wasting and other neurological deficits in the lower extremities.
Trauma can cause fractures to the vertebral body. Additionally, spontaneous compression fractures can occur to older persons with osteoporosis. Due to its loss of normal height, the affected vertebra loses its ability to synergistically move with the other adjacent vertebrae. Compression fractures generally cause pain with certain movements and are generally easily noticeable on x-rays.
Trauma cause fractures can also occur to the facet joints, transverse process or spinous process.
During embryonic development, in some instances spinal segments do not separate completely into individual units, causing fusion of two or three segments. Normal biomechanics, in these situations, are thereby affected. Movements required to compensate for the lack of normal biomechanics can cause degenerative changes and pain.
Persons with this condition demonstrate a hunched posture and difficulty moving the neck. It is due to an inflammatory condition which leads to fusion of spinal vertebrae and the sacroiliac joints of the pelvis.
Two basic types of arthritis occur, and both are inflammatory. Found in weight bearing joints such as the spine, hips and knees, Osteoarthritis is advanced wear and tear of a joint. Rheumatoid arthritis, however, is an auto-immune disease. The finger joints and spine are typically affected.
Bone pathologies, including cancer, can cause back pain.
Chiropractic and other physiotherapy modalities can assist in reducing back pain if it is musculoskeletal in origin. If a pathology or organic etiology is suspected or determined, the patient will be referred to the appropriate specialist.