• STUDY DESIGN
    • Retrospective study.
  • OBJECTIVE
    • To analyze the causes, prevalence of, and risk factors for sagittal thoracic decompensation in adult lumbar spinal instrumentation and fusion (from distal thoracic or upper lumbar spine) to L5 or S1.
  • SUMMARY OF BACKGROUND DATA
    • To our knowledge, no studies on sagittal thoracic decompensation following long adult lumbar spinal instrumentation and fusion (from distal thoracic or upper lumbar spine) to L5 or S1 have been published.
  • METHODS
    • A clinical and radiographic assessment of 99 patients with adult lumbar spinal deformity (average age 56.7 years) who underwent long (> or = 4 vertebrae; range 4-10/average 6.7) spinal instrumentation and fusion (from lower thoracic or upper lumbar spine to L5 or S1) at a single institution between 1985 and 2003 with a minimum 2-year follow-up (average 4.5 years) was performed. We defined sagittal thoracic decompensation as a progressive kyphotic deformity of the thoracic spine without pseudarthrosis after a long lumbar fusion, which subsequently resulted in a C7 plumb relative to the posterior aspect of the L5-S1 disc > or = 8 cm.
  • RESULTS
    • The prevalence of sagittal thoracic decompensation after long adult lumbar spinal instrumentation and fusion (from distal thoracic or upper lumbar spine) to L5 or S1 was 23% (23/99 cases). The etiologies were 14 acute sharp angular kyphoses and 9 long sweeping kyphoses above the instrumented fusion. Of the 14 sharp angular kyphoses, 10 occurred from severe disc degeneration and 4 were caused by compression fractures at the uppermost instrumented vertebra.
  • CONCLUSION
    • Risk factors for sagittal thoracic decompensation developing were sagittal imbalance at 8 weeks postoperatively (> or = 5 cm), smaller lumbar lordosis compared with thoracic kyphosis (< 10 degrees) at 8 weeks postoperatively, preoperative sagittal imbalance (> or = 5 cm), age at surgery (older than 55 years), and associated comorbidities. Sagittal thoracic decompensation adversely affected Scoliosis Research Society 24 outcomes scores.