Assessment of scoliosis correction in relation to flexibility using the fulcrum bending correction index

Abstract

Study Design. A prospective study on adolescent idiopathic scoliosis to assess a new method of describing frontal plane correction. Objective. To assess the difference between using the correction rate and using the new fulcrum bending correction index when describing scoliosis correction. Summary of Background Data. A description of the outcome of scoliosis surgery based on the correction rate does not take into account the curve's flexibility. Methods. The fulcrum bending correction index is calculated by dividing the correction rate by the fulcrum flexibility (based on the fulcrum bending radiograph) and is expressed as a percentage. The fulcrum bending correction index was compared with the correction rate in 35 patients with adolescent idiopathic scoliosis undergoing surgical correction. These patients were divided into a stiff and a flexible group based on a fulcrum flexibility of 50% to show the advantage of the fulcrum bending correction index over the correction rate. Results. The difference in correction rate between the flexible (66%) and the stiff group (45%) was significant (P < 0.05). The difference in the fulcrum bending correction index between the flexible (96%) and the stiff group (107%) was not significant (P = 0.2). Conclusions. The fulcrum bending correction index takes into account the curve flexibility and is therefore better than the correction rate for comparing curve correction and use of instrumentation systems between different series of patients. A fulcrum bending correction index of close to 100% suggests that the instrumentation has taken up all the flexibility revealed by the fulcrum bending radiograph. It is recommended that the fulcrum bending correction index be used in the future as part of the postoperative assessment of frontal plane correction in cases of thoracic scoliosis.