A) Preoperative radiograph of a 17-year-old female after an unsuccessful attempt at fusion for severe slip at 13 years of age (slip, 100%; lumbosacral kyphosis, 60 degrees). B) Lateral radiograph after staged L5 vertebra resection, reduction using halofemoral traction, and instrumented fusion of L4 onto S1. (Operation performed by Dr T. Laine, ORTON Orthopaedic Hospital, Helsinki, Finland.)