Congenital Kyphosis
Definition and Classification
In the first six to eight weeks of embryonic life, a genetic mistake occurs that results in the failure of formation or failure of segmentation on the front part of one or more vertebral bodies and disc. This defect causes the spine to develop a sharp forward angulation as it grows. The forward bend of the spine is called kyphosis and is considered to be congenital as it occurred prior to birth. Congenital kyphosis does not appear to be inherited but rather something that happened for no known reason.
There are two basic types of congenital kyphosis: failure of formation and failure of segmentation. The failure of formation (Type I deformity) of a portion of one or more vertebral bodies most often occurring in the thoracolumbar spine, results in a kyphosis that usually worsens with growth (Figure 1). The deformity is usually visible at birth as a lump or bump on the infant's spine. The failure of segmentation deformity (Type II deformity) occurs as two or more vertebrae fail to separate and to form normal discs and rectangular bones. This type of congenital kyphosis is often more likely to be diagnosed later, after the child is walking.
Figure 1: Congenital kyphosis at the junction of the thoracic and lumbar spine
Evaluation
As with congenital scoliosis, the potential for defects in other organ systems is present. After x-rays confirm the diagnosis, the physician may order additional tests to determine if occult abnormalities are present in the spinal cord, kidneys, cardiac or gastrointestinal system. The MRI provides additional information regarding the abnormal growth potential and may assist in predicting progression of the spinal deformity.
Prognosis
Failure of formation deformity can present with 30 to 60 degree deformities. With the rapid growth of the skeleton in the first year of life, progression is highly likely. Failure of separation (segmentation) deformity has a slower rate of worsening and may not become a surgical curve until adolescence.
Figure 2:
Left: Failure of Formation deformity
Right: Failure of Separation deformity