title: Will immediate postoperative imbalance improve in patients with thoracolumbar/lumbar degenerative kyphoscoliosis? A comparison between Smith-Petersen osteotomy and pedicle subtraction osteotomy with an average 4 years of follow-up.
abstract: METHODS
  A retrospective radiographical study.
  
  
  OBJECTIVE
  To compare compensatory behavior of coronal and sagittal alignment after pedicle subtraction osteotomy (PSO) and Smith-Petersen osteotomy (SPO) for degenerative kyphoscoliosis.
  
  
  BACKGROUND
  There was a paucity of literature paying attention to the postoperative imbalance after PSO or SPO and natural evolution of the imbalance.
  
  
  METHODS
  A retrospective study was performed on 68 consecutive patients with degenerative kyphoscoliosis treated by lumbar PSO (25 patients) or SPO (43 patients) procedures at a single institution. Long-cassette standing radiographs were taken preoperatively, postoperatively, and at the last follow-up and radiographical parameters were measured. The lower instrumented vertebral level and level of osteotomy were compared between the patients with and without improvement.
  
  
  RESULTS
  Negative sagittal vertical axis (SVA) was observed in the PSO group postoperatively, implying an overcorrection of SVA. This negative SVA improved spontaneously during follow-up (P < 0.05). Coronal balance was found to worsen immediately postoperatively in the SPO group (P < 0.05). At the last follow-up, spontaneous improvement was observed in 15 patients and the average coronal balance decreased to 16.35 mm. For the 15 patients with improved coronal balance, fusion at L5 or above was more common compared with the 11 patients with persisted postoperative imbalance (P = 0.027), whereas no difference in term of levels of osteotomy was found (P > 0.05).
  
  
  CONCLUSIONS
  The overcorrection of SVA is more often seen in the PSO group. The coronal imbalance is more likely to occur in the SPO group. The postoperative sagittal imbalance often spontaneously improves with time. Lower instrumented vertebra at S1 or with pelvic fixation should be regarded as potential risk factors for persistent coronal imbalance in patients with SPO.
  
  
  METHODS
  3.
authors.affiliation: From the Spine Surgery, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China.
authors.forename: Hongda
authors.initials: H
authors.lastname: Bao
authors.forename: Shouyu
authors.initials: S
authors.lastname: He
authors.forename: Zhen
authors.initials: Z
authors.lastname: Liu
authors.forename: Zezhang
authors.initials: Z
authors.lastname: Zhu
authors.forename: Yong
authors.initials: Y
authors.lastname: Qiu
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
mesh_terms: D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000009:adverse effects / Q000379:methods*; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology; D011859:Radiography; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome