The lordotic effect of the OSI frame on operative adolescent idiopathic scoliosis patients

Joseph G. Marsicano, Lawrence G. Lenke, Keith H. Bridwell, Michael Chapman, Purnendu Gupta, Joetta Weston

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Study Design. A prospective evaluation of adolescent idiopathic scoliosis patients undergoing operative treatment on the Orthopedic Systems Incorporated (OSI; Jackson) frame. Objectives. To investigate prospectively thoracic, thoracolumbar, and lumbar sagittal alignments in patients with adolescent idiopathic scoliosis who undergo an instrumented posterior spinal fusion on the OSi frame. Summary of Background Data. In several studies, it has been shown that patient positioning on various operative frames is an important component of ultimate lumbar sagittal alignment. However, these studies have all concentrated on the lumbar spine and no sagittal plane alignment data in adolescent idiopathic scoliosis patients have been reported in the thoracic and thoracolumbar junction as it relates to intraoperative positioning, correction maneuvers, and correlative postoperatively results. Methods. Thirty-nine patients with operative adolescent idiopathic scoliosis treated with an instrumented posterior spinal fusion on the OSI frame were prospectively evaluated. Standing preoperative intraoperative, and postoperative long-cassette lateral radiographs were reviewed with regional and segmental Cobb measurements of the thoracic, thoracolumbar junction, and lumbar spine obtained. Results. Thoracic kyphosis (T1-T12) measured +34°before surgery, +28°during surgery and +30°after surgery. Thus, a statistically significant decrease was noted in thoracic kyphosis secondary to prone positioning on the OSI frame (P < 0.05). Thoracolumbar spine measurements from T10 to L2 also showed a lordotic trend from +2°before surgery, to -4°, during surgery, to -8°after surgery, which was also statistically significant (P < 0.05). Total lumbar lordosis from T12 to S1 remained relatively unchanged from -60°before surgery, to -59°during surgery, to -60°after surgery. However, segmental lumbar lordosis measured from T12 to the lowest instrumented vertebra showed a statistically significant increase in lordosis from -17°before surgery, to -19°during surgery, to -23°after surgery (P < 0.05). Those patients in whom lumbar pedicle screws were used (vs. hooks alone) had the greatest increase in lumbar instrumented lordosis. Conclusions. Performing adolescent idiopathic scoliosis correction on the OSI from tends to decrease thoracic kyphosis, increase thoracolumbar lordosis, and increase segmental instrumented lumbar lordosis, while it maintains total lumbar lordosis.

Original languageEnglish
Pages (from-to)1341-1348
Number of pages8
Issue number12
StatePublished - Jun 15 1998


  • Intraoperative positioning
  • OSI (Jackson) frame
  • Sagittal alignment


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