A destructive bone lesion involving the affected vertebral arch and/or vertebral body prior to clinical onset or aggravation of Spondylolysis or Spondylolisthesis
For posterior spinal decompression surgery to cause Spondylolysis or Spondylolisthesis, the surgery may occur any time before clinical onset of either condition.
Type I. Dysplastic: This type results from congenital abnormalities of the upper sacral facets or inferior facets of the fifth lumbar vertebra that allow slipping of L5 on S1. There is no pars interarticularis defect in this type. The sacrum is not strong enough to withstand the weight and stress. Thus, the pars and inferior facets of L5 are deformed. If the pars elongates, it is impossible to differentiate it by x-ray from the isthmic (type II b) Spondylolisthesis. If the pars separates, it becomes impossible to differentiate it by x-ray from the isthmic lytic (type II a) Spondylolisthesis. This type is also associated with sacral and neural arch deficiencies. It has a familial tendency.
The lytic (subtype a) results from the separation or dissolution of the pars. The incidence of this type of Spondylolisthesis increases from less than 1 percent in children 5 years of age to 4.5 percent in children 7 years of age. The remaining 0.8 to 1 percent increase occurs between the ages of 11 to 16 years, presumably because of stress fractures caused by athletic activity. Extension movements of the spine, with lateral flexion, can increase the shearing stress at the pars interarticularis and result in Spondylolysis.
Spondylolysis and Spondylolisthesis usually cause no symptoms in children; however, many seek medical evaluation because of a postural deformity or gait abnormality. Pain most often occurs during the adolescent growth spurt and is predominantly backache, with only occasional leg pain. Symptoms are exacerbated by high activity levels or competitive sports and are diminished by activity restriction and rest. The back pain probably results from instability of the affected segment, and the leg pain is usually related to irritation of the L5 nerve root.
Spondylolisthesis by its nature causes instability of the spine. This instability has an adverse effect on the disc immediately below the displaced vertebra and can influence the development of degenerative changes to a moderate to severe degree.
Posterior spinal decompression surgery, at the level of the involved vertebra, prior to clinical onset or aggravation of Spondylolysis or Spondylolisthesis