What is the pathophysiology of kyphosis?

Updated: May 04, 2020
  • Author: R Carter Cassidy, MD; Chief Editor: Jeffrey A Goldstein, MD  more...
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Answer

The pathophysiology of kyphosis depends on the etiologic factor. The exact cause of Scheuermann disease is still imprecisely defined. Scheuermann postulated that the condition resulted from avascular necrosis of the apophyseal ring. Other theories include histologic abnormalities at the endplate, osteoporosis, [3] and mechanical factors that affect spinal growth. [4] A Danish study demonstrated an important genetic component to the entity. [5]

Postural kyphosis is present when accentuated kyphosis is observed without the characteristic 5° of wedging over three consecutive vertebral segments that defines Scheuermann kyphosis. [6] This is felt to be due to muscular imbalance leading to the round-back appearance of these individuals.

It is noteworthy that hyperkyphosis in persons older than 60 years is usually not due to underlying vertebral fractures, which are only found in a minority (≤37%) of patients with hyperkyphosis; it is more often due to disk degeneration, muscle imbalance, and overall change in the shape of the aging spine. This kyphosis is associated with increased fracture risk, poorer pulmonary function, poorer physical function, and increased risk of death, even in those without fracture and osteoporosis. [7]

Familial hyperkyphosis may be related to the inherited pattern of disk degeneration. As disk height is lost, as part of normal aging and degeneration of a disk, the kyphosis increases. As more disks become involved, the effect is potentiated, and the overall kyphosis becomes more significant. 

When focal kyphosis occurs after a fracture, more height is lost in the anterior aspect than in the posterior aspect; this is the typical fracture pattern. The angulation can increase as the fracture heals, placing pressure on the spinal cord and further pressure on the anterior column of the spine. Patients with fractures have historically been treated with laminectomy alone, especially in the thoracic spine, and they often had progressive kyphosis at the fracture site. [8, 9]

Postinfectious kyphosis occurs in a manner similar to that just described. Mechanical integrity of the anterior column is lost as a consequence of the infectious process. Bending forces then accentuate the normal sagittal contour.


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