title: Correlation between preoperative spinopelvic alignment and risk of proximal junctional kyphosis after posterior-only surgical correction of Scheuermann kyphosis.
abstract: BACKGROUND
  Surgical correction of Scheuermann kyphosis (SK) is challenging and plagued by relatively high rates of proximal junctional kyphosis and failure (PJK and PJF). Normal sagittal alignment of the spine is determined by pelvic geometric parameters. How these parameters correlate with the risk of developing PJK in SK is not known.
  
  
  OBJECTIVE
  The study aimed to investigate the relationship between preoperative and postoperative spinopelvic alignment and occurrence of PJK and PJF.
  
  
  METHODS
  This is a retrospective observational cohort study.
  
  
  METHODS
  The sample included 37 patients who underwent posterior correction of SK from January 2006 to December 2012.
  
  
  METHODS
  The outcome measure was correlation analysis between preoperative and postoperative spinopelvic alignment parameters and the development of PJK over the course of the study period.
  
  
  METHODS
  Whole spine x-rays obtained before surgery, 3 months after surgery, and at the latest follow-up were analyzed. The following parameters were measured: thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). The development of PJK was considered the primary end point of the study. Patient population was split into a control and a PJK group; repeated-measures analysis of variance was used to assess group and time differences.
  
  
  RESULTS
  Seven patients developed PJK over the study period. Although the severity of the preoperative deformity (TK) did not differ significantly between the two groups, preoperative PI was significantly higher in the PJK group (51.9°C±8.6°C vs. 42.7°C±8.8°C, p=.018). Postoperative correction of TK was similar between the two groups (39.3% and 41.2%, p=.678) and final LL did not differ as well (53.6°C±9.2°C vs. 51.3°C±11.5°C). However, because PJK patients had larger preoperative PI values, a significant deficit of LL was observed at final follow-up in this group compared with the control group (ΔLL -10.5°C±9.8°C vs. 0.6°C±10.5°C, p=.013).
  
  
  CONCLUSIONS
  Scheuermann kyphosis patients who developed PJK appeared to have a significant postoperative deficit of LL (lumbopelvic mismatch). Lumbar lordosis decreases after surgery following correction of TK; therefore, TK correction should be planned according to preoperative PI values to avoid excessive reduction of LL in patients with higher PI values.
authors.affiliation: The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Rd, Nottingham NG7 2UH, UK. Electronic address: luigiaurelionasto@yahoo.it.
authors.forename: Luigi A
authors.initials: LA
authors.lastname: Nasto
authors.affiliation: The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Rd, Nottingham NG7 2UH, UK.
authors.forename: Ana Belen
authors.initials: AB
authors.lastname: Perez-Romera
authors.affiliation: The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Rd, Nottingham NG7 2UH, UK.
authors.forename: Saggah Tarek
authors.initials: ST
authors.lastname: Shalabi
authors.affiliation: The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Rd, Nottingham NG7 2UH, UK.
authors.forename: Nasir A
authors.initials: NA
authors.lastname: Quraishi
authors.affiliation: The Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Rd, Nottingham NG7 2UH, UK.
authors.forename: Hossein
authors.initials: H
authors.lastname: Mehdian
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000209:etiology*; D008141:Lordosis / Q000000981:diagnostic imaging / Q000209:etiology*; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D019637:Orthopedic Procedures / Q000009:adverse effects*; D010388:Pelvis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D012447:Sacrum / Q000000981:diagnostic imaging / Q000503:physiopathology; D012544:Scheuermann Disease / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000503:physiopathology; D017211:Treatment Failure
keywords: Kyphosis correction; Lumbopelvic mismatch; Proximal junctional kyphosis (PJK); Sagittal balance; Scheuermann kyphosis; Spinopelvic parameters