Comparison of push-prone and lateral-bending radiographs for predicting postoperative coronal alignment in thoracolumbar and lumbar scoliotic curves

Study Design. A comparative evaluation of supine right and left lateral-ben ding radiographs and push-prone radiographs in patients with thoracolumbar and lumbar scoliosis to determine postoperative correction of the curve. Objectives. To determine the difference in the ability of the push-prone ra diograph and the supine lateral-bending radiograph to predict postoperative coronal alignment for primary thoracolumbar and lumbar curves managed with an anterior spinal instrumentation and fusion. Summary of Background Data. Right and left supine side-bending radiographs are the standard means of evaluating curve flexibility before surgery in id iopathic scoliosis. A push-prone radiograph also has been obtained at the a uthors' institution as a single dynamic radiographic assessment of forced c orrection of the primary curve and resultant effects on compensatory curves above and below the fusion. Methods. Preoperative standing, supine right and left lateral-bending, and push-prone radiographs were performed in 40 patients who underwent anterior spinal instrumentation and fusion, Postoperative standing radiographs of t he spine were obtained at 3 months after surgery. Measurements on all the r adiographs included the coronal Cobb angle, the angle of the lowest instrum ented vertebra to the horizontal, the rotation of the lowest instrumented v ertebra, and the distance of the midpoint of the lowest instrumented verteb ra from the center sacral line. Results. The lateral-bending and the push-prone radiographs predicted less correction of the Cobb angle and the angle of the lowest instrumented verte bra to the horizontal than was achieved after surgery. However, the posh-pr one radiograph was superior to the lateral-bending radiograph in accurately predicting the postoperative;l-correction of the rotation of the lowest in strumented vertebra as well as the translation of the lowest instrumented v ertebra from the center sacral line. Conclusions. The push-prone and lateral-bending radiographs are similar in predicting less correction of the Cobb angle after anterior spinal surgery. The push-prone radiograph helps in determining the effects that correction of the primary curve has on the curves above and below the level of fusion by better predicting the translational correction of the lowest instrument ed vertebra and the rotation of the lowest instrumented vertebra.