A retrospective study is reported of 36 children and adolescents who had undergone spinal exploration and fusion for Type I of Type II spondylolisthesis of more than 10 per cent. The patients were examined and their radiographs studied. No progression of slip after operation was found even in the presence of a pseudarthrosis. Where altered mobility was present at the level above the fusion, this tended to be associated with pain. Posterolateral fusion relieved symptoms in 75 per cent, produced a sound fusion in 83 per cent and prevented further slip in all patients.

A study of spondylolysis and spondylolisthesis in 142 children and adolescents is reported. In twelve of the seventy-nine patients followed for over a year the affected vertebra slipped further by 10 per cent or more. Increasing slip occurred mainly during the adolescent growth spurt, and was greater when spinal bifida or other vertebral anomalies were present. If at presentation the slip is less than 30 per cent then further slip beyond 30 per cent is unlikely. Decompression posteriorly is advised when signs of nerve pressure are present. Indications for spinal fusion are suggested; the intertransverse method of fusion was used in sixty-nine patients.