The term, spondylolisthesis, is used to describe forward displacement of one vertebral body on another. Such a displacement frequently occurs at the lumbosacral junction in association with a defect, called spondylolysis. in the fifth lumbar (L5) isthmus (pars interarticularis) on each side. Spondylolisthesis may also develop secondary to degenerative changes of the facet joints and intervertebral disc between adjacent spinal segments; this frequently occurs between the L4 and L5 vertebral segments. Most patients with spondylolisthesis present with low back pain, and plain radiographs are usually sufficient for diagnosis. Although the majority of patients will obtain pain relief from conservative measures, some will require neural decompression, bony fusion, or spinal instrumentation.

Incidence

With the exception of 1 reported case, spondylolysis is not present at birth. One study reported a prevalence of 4.4% in children aged 6 years, with prevalence increasing to 5.4% by adulthood. It is presumed that the
increase is related to the adolescent growth spurt. In the same study, prevalence of spondylolisthesis was reported to be 2.6% and 4.0%, respectively.

Dysplastic spondylolisthesis represents approximately 14-21% of all cases of spondylolisthesis. Eskimos have a reported incidence of spondylolysis in adults of almost 50%, which is presumed to result from a combination of genetic and environmental factors.

Mortality/Morbidity

Mortality has never been reported in spondylolisthesis. Morbidity is not uncommon, since back pain and neural involvement, if severe enough, can affect activities of daily living.

Race

The white population is affected more frequently with spondylolysis than is the black population. Eskimos also have a high incidence. The degenerative form has a higher prevalence in the black population.

Sex

Spondylolysis has a 2:1 male-to-female predominance; the congenital and degenerative forms of spondylolisthesis have a female-to-male predominance of 2:1 and 5:1, respectively.

Age

Spondylolysis, with the exception of 1 reported case, is not present at birth. Its appearance develops with increasing age, in keeping with the presumed pathogenesis relating to increasing activity and spinal loading. At age 6 years, a 4.4% prevalence is reported; a 5.4% prevalence is reported in adulthood. Consequent spondylolisthesis has a reported prevalence of 2.4% and 4.0%, respectively. Congenital spondylolisthesis may be seen in early life, but patients usually present with symptoms during the adolescent growth spurt.

Anatomy

In a healthy person, the facet joint in the lumbar spine is, for the most part, in the coronal plane, with the inferior articular process (of the superior vertebra) located posteriorly and the superior articular process (of the inferior vertebra) located anteriorly. This configuration prevents forward movement of the vertebrae relative to each other. It locks in the superior vertebra relative to the inferior vertebra, which is important, since the center of gravity of the human body is located anterior to the spine. This mechanism exerts a forward slipping force on the spine, especially at the L5-S1 level. Furthermore, the anteriorly located center of gravity causes a rotating movement, with the axis of rotation oriented transversely at the L5-S1 level. Thus, in severe spondylolisthesis, a kyphotic deformity also develops.