Comparison of pre-operative correction X-rays with post-operative correction achieved in adolescent idiopathic scoliosis

Aim: To determine how accurately pre-operative stress radiographs predict the final outcome in adolescent idiopathic scoliosis surgery. Methods: Records of 20 patients were reviewed retrospectively. Pre-operative correction was measured by comparing the initial Cobb angle of the main structural curves on plain standing radiographs to values measured at corresponding levels after correction on traction and fulcrum bending radiographs. Post-operative correction was obtained by measurements at corresponding levels of the instrumented and uninstrumented curves. Results: Mean correction of the main instrumented curve by traction was 24.2° (40.9%), and by fulcrum bending 32.3° (56.0%). Post-operative correction yielded a mean value of 41.1° (68.2%). Expressing pre-operative values as a percentage of final correction, traction views predicted 60%, and fulcrum bending radiographs 82% of the final correction. If agreement within 10° of preand post-operative values is regarded as clinically significant, only 18% of traction and 45% of fulcrum bending views came within that range. Discussion: We concluded that fulcrum bending views are of superior predictive value in terms of surgical correction to be expected, but still correlate poorly with final surgical correction achieved. Introduction Pre-operative assessment of the flexibility of scoliotic curves provides the surgeon with some information regarding the levels to be included in arthrodesis, the amount of correction that can be achieved safely if an anterior release is required, and whether a secondary curve should be treated with arthrodesis or not. Unfortunately the results of these stress views often bear little relation to the final surgical correction achieved. Methods employed to determine the flexibility of the curves include Cobb angle comparisons between standing and supine radiographs, traction radiographs, push prone radiographs, lateral bending radiographs with the patient supine or standing, and fulcrum bending radiographs. SAOJ Summer 2009 11/26/09 4:35 PM Page 18