Introduction to Spondylolisthesis

Causes of Spondylolisthesis

Spondylolisthesis can be caused by various conditions including:

• Spondylolysis
• Congenitally dysplastic joints
• Genetic factors
• Trauma

Spondylolysis

Researchers believe that most children with spondylolysis may be born with a weak pars and repeated stress between the ages of 8 and 14 causes stress fractures that ultimately may evolve into spondylolisthesis. Biomechanical studies suggest that the pars is the weakest part of the posterior neural arch which may predispose it to injury with certain repetitive motions.

There is also evidence that slippage may be due to elongation of the pars which may result in repetitive microfractures with subsequent healing of the pars in an elongated position. Elongation of the pars can also be a congenital condition.

Congenitally Dysplastic Joints

Children who are born with dysplastic (underdeveloped) facet joints, which affect the stability of the vertebrae, may develop slippage of one vertebra over another.

Genetic Factors

Evidence of a genetic link can be ascertained by the increased incidence of spondylolysis in first-degree relatives of individuals with either congenital or isthmic spondylolisthesis. Certain ethnic groups have very high rates of spondylolysis that also indicates a genetic component. For example, spondylolysis occurs in up to 50% of Eskimos while African Americans only have an incidence of only approximately 1.5%.

Trauma

Trauma can lead to spondylolisthesis by a variety of different mechanisms:

• traumatic fracture of the pars interarticularis
• traumatic fracture of the articular processes of the vertebrae
• traumatic fracture of the facet joints
• traumatic subluxation or dislocation of the facet joints