Quantifying changes in standing body segment alignment following spinal instrumentation and fusion in idiopathic scoliosis using an optoelectronic measurement system

Study Design. Longitudinal case studies before and after posterior spinal instrumentation and fusion (PSIF) in idiopathic scoliosis (IS). Objectives. To quantitate the changes in body seg ment alignment following PSIF using standard radiographic techniques and an optoelectronic measurement system. Summary of Background Data. Evaluation of surgical correction following PSIF is traditionally performed radiographically. Radiographic film cannot reliably document transverse and coronal plane pelvic, torso, and shoulder orientation resulting from the global effect of vertebral malalignment. Methods. Thirty-three subjects with IS were evaluated radiographically and with an optoelectronic measurement system before and 13 months after PSIF. All subjects had a primary right thoracic curve pattern. Thirteen :subjects without scoliosis were evaluated as controls. Symmetry measures and transverse and frontal plane orientation relationships were measured and compared preop, postop, and with controls. Results. The major curve decreased from 60 degrees to 24 degrees after surgery. The magnitude of C7 decompensation from the sacrum decreased following PSIF. Control subjects demonstrated neutral coronal acid transverse plane alignment. Preoperatively, patients had an elevated and protracted right shoulder. Postoperative data showed correction in-both the coronal and transverse planes. Ten out of 33 subjects were within 5 degrees of neutral shoulder protraction before surgery. Twenty-six out of 33 were within 5 degrees of neutral following surgery. Conclusions. Optoelectronic measurement of body Segment alignment may be a useful noninvasive technique in the evaluation of scoliotic deformity. This is a new method of evaluating the global effect of vertebral malalignment on body segment alignment and can be used to quantify changes following PSIF.