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Back pain and sciatica

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of back pain, including sciatica.

Alternative Names

Herniated disk; Sciatica

Introduction

Back pain is one of the most common reasons people visit their doctor. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, 8 out of 10 people have some type of backache.

Back pain can be acute or chronic.

• Acute pain develops suddenly and goes away within 6 weeks. Acute pain is the most common type of back pain.
• Chronic pain can come on fast or slow, but it lasts longer than 3 months. Back pain can occur in any area of the back, but it is more common in the lower part, which supports most of the body’s weight.

The Spine

The back is highly complex, and pain may result from damage or injury to any of various bones, nerves, muscles, ligaments, and other structures. Still, despite sophisticated techniques that provide detailed anatomical images of the spine and other tissues, the cause of most cases of back pain remain elusive.

Vertebrae. The spine is a column of small bones, or vertebrae, that support the entire upper body. The column is grouped into three sections.

• The cervical (C) vertebrae are the seven spinal bones that support the neck.
• The thoracic (T) vertebrae are the twelve spinal bones that connect to the rib cage.
• The lumbar (L) vertebrae are the five lowest and largest bones of the spinal column. Most of the body's weight and stress falls on the lumbar vertebrae.

Below the lumbar region is the sacrum , a shield-shaped bony structure that connects with the pelvis at the sacroiliac joints.

At the end of the sacrum are two to four tiny, partially fused vertebrae known as the coccyx or "tail bone."

Each vertebra is designated by using a letter and number, which allows the doctor to determine where it is in the spine.

• The letter reflects the spinal region where the vertebra is located: C=cervical (neck region), T=thoracic (chest, or middle back, region), and L=lumbar (lower back).
• The number signifies the vertebra's place within that spinal region. The numbers start with 1 at the top of a region and count up as the vertebrae descend within the region. For example, C4 is the fourth bone down in the cervical region and T8 is the eighth thoracic vertebrae.

The Disks. Vertebrae in the spinal column are separated from each other by small cushions of cartilage known as intervertebral disks . The disks have no blood supply of their own. They need to rely on nearby blood vessels to keep them nourished.

Each disk is 80% water and contains two structures.

• Inside each disk is a jelly-like substance called the nucleus pulposus.
• The nucleus pulposus is surrounded by a tough, fibrous ring called the annulus.

Processes. Each vertebra in the spine has a number of bony projections called processes . The spinal and transverse processes attach to the muscles in the back and act like little levers, allowing the spine to twist or bend. The particular processes form the joints between the vertebrae themselves, meeting together and interlocking at the zygapophysial joints (more commonly known as facet or z joints ).

Spinal Canal. Each vertebra and its processes surround and protect an arch-shaped central opening. These arches, aligned to run down the spine, form the spinal canal, which encloses the spinal cord.

Spinal Cord. The spinal cord is the central trunk of nerves that connects the brain with the rest of the body. Each nerve root passes from the spinal column to other parts of the body through small openings bounded on one side by the disk and the other by the facets. When the spinal cord reaches the lumbar region, it splits into four bundled strands of nerve roots called the cauda equina (meaning horsetail in Latin).

• Review Date: 3/19/2007
• Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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