title: Risk factors of sagittal decompensation after long posterior instrumentation and fusion for degenerative lumbar scoliosis.
abstract: METHODS
  A retrospective study of clinical results of operative treatment for degenerative lumbar scoliosis.
  
  
  OBJECTIVE
  To determine the risk factors of sagittal decompensation after long instrumentation and fusion to L5 or S1.
  
  
  BACKGROUND
  Little is known about the risk factors for sagittal decompensation, which was defined in this study as sagittal C7 plumb falling anterior >8 cm from the posterosuperior corner of the sacrum.
  
  
  METHODS
  Forty-five patients (mean age: 64.4 year) with adult degenerative lumbar scoliosis were reviewed retrospectively with a minimum 2 years. The mean number of levels fused was 6.1 +/- 1.6 segments. The upper instrumented vertebra ranged from T9 to L2. The lower instrumented vertebra was L5 and S1 in 24 and 21 patients, respectively.
  
  
  RESULTS
  Sagittal decompensation (SD) developed in 19 patients. The most significant risk factors of SD were preoperative sagittal imbalance and high pelvic incidence. The preoperative sagittal C7 plumb was more positive (67.9 mm) in the decompensation group than in the balance group (37.0 mm) (P = 0.002). There was a significant difference in pelvic incidence between 61.7 degrees in the decompensation and 54.9 degrees in the balance group (P = 0.01). The preoperative lumbar lordosis was hypolordotic in the decompensation group, however, it was not found to be a risk factor. Pseudarthrosis was identified at the lumbosacral junction in 5 patients, and 4 of them (80%) had SD. SD developed in 55% of patients who had loosening of the distal screws and 50% of patients with hypolordotic lumbar fusion. Distal adjacent segment disease was more likely to cause SD than proximal adjacent segment disease.
  
  
  CONCLUSIONS
  Sagittal decompensation is common after long posterior instrumentation and fusion for degenerative lumbar scoliosis. It is mostly associated with complications at the distal segments, including pseudarthrosis and implant failure at the lumbosacral junction. Restoration of optimal lumbar lordosis and secure lumbosacral fixation is necessary especially in patients with preoperative sagittal imbalance and high pelvic incidence in order to prevent sagittal decompensation after surgery.
authors.affiliation: Department of Orthopaedic Surgery, Inha University Hospital, Incheon, Republic of Korea.
authors.forename: Kyu-Jung
authors.initials: KJ
authors.lastname: Cho
authors.forename: Se-Il
authors.initials: SI
authors.lastname: Suk
authors.forename: Seung-Rim
authors.initials: SR
authors.lastname: Park
authors.forename: Jin Hyok
authors.initials: JH
authors.lastname: Kim
authors.forename: Suk-Bong
authors.initials: SB
authors.lastname: Kang
authors.forename: Hyung-Suk
authors.initials: HS
authors.lastname: Kim
authors.forename: Seung-Jae
authors.initials: SJ
authors.lastname: Oh
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000209:etiology*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D012447:Sacrum / Q000601:surgery*; D012600:Scoliosis / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation; D018709:Statistics, Nonparametric; D013904:Thoracic Vertebrae / Q000601:surgery*