The defect in the pars interarticularis in spondylolysis and
spondylolisthesis is most often the result of repeated trauma, stress, and
factors other than acute fracture. These fatigue fractures develop early in
life, may have a strong hereditary basis, and most often represent
incidental roentgenographic findings. Attention should be given to the
youngster or adolescent with low-back pain and paraspinal muscle spasm. If
these patients are followed closely, the incidence of pars interarticularis
defect is higher than appreciated. The lesion in some of these individuals
may progress to significant vertebral slipping. If the developing defect is
recognized early, treatment can be quite satisfactory.