Anatomy

Before exploring the causes of and treatment for neck and back pain, it is important to understand a bit about the make-up — or anatomy — of the spine. The spine is composed of a complex arrangement of bones, muscles, ligaments, and blood vessels surrounding the nerves and spinal cord. This complex structure allows for flexible movement and provides protection for the nerves and spinal cord that convey information about the body to the brain. The spine is often considered the "axis" upon which the rest of the body, including the skull and limbs, are built. Viewed from the side, a normal spine is shaped like a gentle double S curve. The curves are necessary for normal balance and posture.

The spine is divided into five basic vertebral groups. In order from top to bottom, they are:

• The Cervical or neck area – consisting of seven segments or vertebrae
• The Thoracic or dorsal area – consisting of twelve segments or vertebrae each associated with a rib.
• The Lumbar or low back area – consisting of the largest five vertebrae
• The Sacrum – consisting of five segments joined together before birth and joins together the pelvic bones
• The Coccyx – generally consisting of four (and sometimes less or more) segments, which in other animals form the tail

Each vertebra has two main parts: the vertebral body and, behind but attached to the vertebral body, the vertebral arch that forms the roof of the spine or lamina, the junction or joints between the vertebrae known as facets, and the posts, known as pedicles, which attach these structures to the vertebral body. The sensitive spinal cord passes through this arch and is protected by it. Each vertebral body is separated from the other by a structure known as a disc. This somewhat complicated structure consists of an outer covering that is quite strong called the annulus. The word annulus means ring in Latin and describes how this structure looks under the microscope. Inside the annulus and surrounded by it is a soft cushion-like material known as the nucleus pulposus. The disc acts like a shock absorber, supporting about 90 percent of the weight of the upper body and allowing flexibility. Several strong ligaments in the front, sides, and back of the vertebral discs protect and join them to the vertebral body. Strong muscles attached to the spinal column provide stability and strength to the spine.

It is important to recognize that each segment of the spine works in conjunction with all other parts of the spinal column. The spine is a complex and marvelously dynamic structure constantly in movement. This structure allows for bending forward (flexion), bending backward (extension), bending sideways (lateral flexion), and rotational movement (twisting).

The spinal column, as previously described, contains the spinal cord that begins in and is attached to the lower part of the brain and ends at about upper lumbar vertebra. This structure carries messages to and from the brain and different parts of the body.  Such messages are carried in nerves that divide at the spine into nerve roots entering and leaving the spinal column through openings known as windows or foramina. These openings often are narrowed by disease, such as arthritis, or swelling, bulging or herniation of the vertebral discs, leading to the term "pinched" nerve.

Back pain may arise from one or more  spinal structures. Despite advances in technology, in up to 80 percent of cases it is extremely difficult to diagnose the origin of the pain. Back pain can arise from any of the following areas:

·         Bone and joint pain – often described as a "rusty hinge" sensation that can be worse during cold weather and in the mornings, and gets a little better with movement and a hot shower. Such pain can be associated with a fracture of the spine, dislocation of bones, arthritis (inflammation) of the facet joints, infection of the bone, or, in a very small number of cases,  with abnormally developed bones in the back or neck.

·         Soft tissue pain – often called muscle or ligament pain and described as "aching, cramping and knotty." Such pain is associated with recent activity and improved with stretching and massage. Discogenic pain, in which the soft material inside the disc breaks out through a tear in the annulus, may be included here. This condition often is described as a "burning sensation with an underlying aching feeling." Pressure from disc material on the overlying nerve root can result in the burning, stinging, radiating, and sometimes electric-shock-like pain known as nerve root or radicular pain. In the legs, this type of pain is known as sciatica. The nerve roots involved often proceed down the back of the leg into the foot where this pain is felt. A similar type of pain can be felt in the arms when pressure is placed on a cervical nerve root in the neck area.

·         Nerve pain – in fact all pain results from an interpretation by the brain of information traveling in nerves. A feeling of pain occurs when a nerve is swollen, "angry," compressed or restricted by scar tissue and is injured or about to be injured. Nerve pain often is described as "sharp," "knifelike" and "piercing." (See discogenic pain, sciatica.)

·         Discogenic pain - a structural abnormality within the disc itself, this pain may be termed an annual tear or central disc herniation.

·         Other Causes – Back and neck pain may be a symptom of disease or inflammation of other organs such as the uterus in the pelvis, a kidney stone, an aneurysm or swelling of the aorta, the major abdominal blood vessel, or a warning symptom of cancer, infection or trauma. Most often such back pain is not related to activity or rest. It consistently may be worse at night, or during a specific time of day.

Soft Tissue and Bone Pain

Three mechanisms are primarily responsible for this type of pain: thermal, chemical and mechanical irritants. This means that excessive heat, irritating chemicals and abnormal mechanical forces, such as excessive stretching, crushing or breaking, cause the pain and the accompanying inflammation. In medical terms, muscle/bone pain is called nociceptive because receptors for these irritants are activated and send messages warning of tissue damage or impending tissue damage to the brain. The receptors may be activated on the exterior of the body, such as muscles and joints, or inside the body as in the abdominal organs or viscera and other areas. 

Nerve Pain

Nerve pain usually is not—but can be—inflammatory or related to muscle and bone (nociceptive). The technical term for pain due to nerve injury is neuropathic pain.  Such pain typically is described as "knifelike, sharp, lightning bolt", rather than as the "rusty hinge" sensation associated with bone pain or the "knotted rope" feeling of muscle pain.  Nerve pain is sub-classified as peripheral nerve pain or central nerve pain. Some authorities add a third category known as sympathetically mediated nerve pain, or pain involving the autonomic nervous system.

Often, in the case of back and neck pain, nerve pain radiates into the legs from the back or into the arms from the neck. In terms of back and neck pain, nerve pain typically results from the irritation of the nerve by substances such as leaking material from a degenerated or herniated disc; by pressure on the nerve caused by infection, disc herniation or a tumor; and by a nerve being entrapped by scar tissue or other body structures, such as ligaments.

 Nerve pain also can be caused when a nerve is damaged from an injury, surgery, diseases such as diabetes or herpes zoster (shingles), or by the toxic effects of chemicals, such as chemotherapy and radiation used in cancer treatment.

In each of these cases, damaged nerves send abnormal pain signals, even after the associated injury or damaged tissue has healed.

Traumatic and Non-Traumatic Causes of Pain

For diagnostic purposes, after classifying the pain as nociceptive (muscle/bone) or neuropathic (nerve), some physicians further divide back or neck pain into traumatic (resulting from an accident or injury) or non-traumatic in origin.

Traumatic causes are then subdivided into two main causes—micro and macro:

• Micro causes are typically overuse injuries such as physically stressful activities and strains and sprains. 

•  Macro causes are injuries resulting from a single event such as a blow or injury.

Non-traumatic causes are defined as degenerative, caused either by aging or related to diseases such as arthritis, and systemic such as infections or resulting from a cancer.

Traumatic Causes- Examples include:

•  Physically stressful repetitive activities or overwork.

• Disc-related injuries.

• Fractures.

• Ligament sprains and strains.

• Fractures caused by osteoporosis.

• Compressions of nerves and spinal cord structures.

Non-traumatic Causes

• Poor posture or being overweight.
• Menstruation.
• Degenerative problems caused by the aging process, forms of arthritis and degenerative disc disease.
• Muscle spasms.
• Inflammation from strains and sprains.

•  Hematoma (a swelling caused by bleeding within the tissues).

• Infections in various parts of the body, such as the kidney, bladder or teeth.
• Infectious diseases such as meningitis.
• Neoplasm, or soft tissue tumors, and bone cancer.
• Discitis, an inflammation in the disc, usually related to infection and may be spontaneous or related to a medical procedure carried out within the disc.
• Congenital problems of the spine that lead to instability or dislocation when associated with degenerative changes or trauma. One such relatively common example is spondylolysis (an absence of the bony connection between the lamina or roof of the spine and the joint), which may lead to spondylolisthesis (a forward slippage or dislocation of the spine as spondylolysis triggers the loss of disc support).