What is Kyphosis?

By , MD, PhD

Kyphosis is a term used to describe marked curvature of the spine in the sagittal plane that results in an abnormally rounded back. Certain degree of kyphosis is normally present at the thoracic and sacral spinal segments. If the curve of a person's thoracic spine exceeds 40 to 45 degrees, it is considered abnormal.

Degenerative disc diseases, inflammation, trauma, developmental anomalies and infectious diseases are the known causes of kyphosis. It can be generally divided into two types: low degree kyphosis (such as postural roundback) and high degree kyphosis (Scheuermann's disease, angular gibbus deformity, congenital kyphosis, Pott disease). Kyphosis may also develop due to the muscular and neuromuscular diseases.

Common types of kyphosis

Postural kyphosis (round back) is a flexible kyphosis typically not associated with pain. Slouching during childhood affects the normal development of the spine, causing it to curve forward. This type of kyphosis is often accompanied by hyperlordosis of the lumbar spine – an excessive curvature of the lower spine in the opposite direction.

A postural kyphosis corrects itself when lying down on a horizontal surface, or when the spine is hyper-extended. No vertebral abnormalities are seen on X-rays, because this kypohsis is not caused by deformity or structural damage. In fact, the condition is rather easily corrected with education about proper posture, strengthening the back muscles and retraining on how to sit and stand correctly.

Scheuermann's kyphosis (or Scheuermann's disease) is defined as thoracic kyphosis greater than 45 degrees with greater than 5 degrees of anterior wedging in 3 adjacent vertebrae. It represents the most common severe form of thoracic kyphosis in adolescence, with reported prevalence of 1 to 8%. Schmorl's nodes (small herniations of intervertebral dics) are also present at the ends of the affected vertebrae.

The biggest difference from postural kyphosis is that a patient suffering from Scheuermann's kyphosis cannot consciously correct posture due to the rigidity of the curve. Although the exact cause remains unclear, there are many possible theories about its development. Most researchers consider that the process is started by some sort of damage to the growth area of the vertebrae, resulting in an abnormal growth and subsequent excessive kyphosis.

Congenital kyphosis refers to inherited abnormal development of the spine when the individual is born with some sort of defect that can lead to a severe abnormal kyphosis. This kyphosis also represents the most common non-traumatic, non-infectious cause of paraplegia. There is a strong association of such congenital abnormalities with the body's urinary tract, which can be helpful in diagnosing this condition.

Spinal tuberculosis (Pott’s kyphosis) is the most common cause of a kyphotic spinal deformity in large parts of the world. Tuberculosis has a preference for the anterior segment of the vertebral column in more than 90% of the patients, and the most severe deformities are seen in children involving the thoracolumbar spine. Such kyphosis can progress even after healing of the spinal infection.

Injury of the spine can result in both progressive kyphosis and nerve problems. When there is a vertebral fracture in the thoracic or lumbar spine, in 90% of cases some degree of kyphosis will ensue. It can also arise following surgery of the spine due to other indications. Degeneration of the lumbar spine results in a gradual development of kyphosis.

Ways to diagnose the condition

Taking patient's history is a first step in making a accurate diagnosis and ruling out other conditions, as early detection of kyphosis is pivotal for successful treatment. The clinical interview is used to collect important information, such as the date of onset of the deformity, the occurrence of pain, eventual progression over time, any treatments used so far, as well as other health problems in the patient or family.

During the exam, the health-care provider will try to get a proper understanding of the spinal curve and the way it is affecting the patient. The spine should be assessed from the sides, front and back after the patient is undressed. If the deformity disappears completely when the child is asked to stand up, the most likely diagnosis is postural kyphosis.

Usually full-length antero-posterior and lateral radiographs are ordered that allow proper visualization of the spinal structure. Computerized tomography (CT) of the spine provides supplemental information on eventual bone abnormalities predating or caused by the kyphosis. With magnetic resonance imaging (MRI) it is possible to assess junction of the spinal joints as well as to asses if there is an impingement on the spinal canal of bone structures.

A detailed neurological evaluation is often obligatory. Special attention should be given to assess deep tendon reflexes, superficial abdominal reflexes and eventual presence of hypertonia. Other specific investigations may be attained when needed, such as lung function testing, a spinal cord arteriogram, an intradermal tuberculin test, ultrasonography of the kidneys, echocardiography or other.

Further Reading

Last Updated: Nov 30, 2014

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