title: Acute proximal junctional failure in patients with preoperative sagittal imbalance.
abstract: BACKGROUND
  Proximal junctional failure (PJF) is a recognized complication of spinal deformity surgery. Acute PJF (APJF) has recently been demonstrated to be 5.6% in the adult spinal deformity (ASD) population. The incidence and rate of return to the operating room for APJF have not been specifically investigated in individuals with sagittal imbalance.
  
  
  OBJECTIVE
  The purpose of this study was to report the incidence of APJF in patients with preoperative sagittal imbalance and the rate of return to the operating room for APJF.
  
  
  METHODS
  This study is based on a retrospective review of prospectively collected database of ASD patients.
  
  
  METHODS
  One hundred seventy-three consecutive patients were included with preoperative sagittal imbalance according to one of the following common parameters: sagittal vertical axis (SVA) greater than 50 mm, global sagittal alignment greater than 45°, or pelvic incidence minus lumbar lordosis greater than 10°.
  
  
  METHODS
  Outcome measure was presence and/or absence of APJF defined as fracture at the upper instrumented vertebra (UIV) or UIV+1, failure of UIV fixation, 15° or more proximal junctional kyphosis, or need for extension of instrumentation within 6 months of surgery.
  
  
  METHODS
  We performed radiographic measurements on X-rays at preoperative, immediate postoperative, and 6-month follow-up visits. The APJF rate was reported for the entire patient population with preoperative sagittal imbalance. Acute PJF incidence was calculated postoperatively for each of the accepted sagittal balance parameters and/or formulas. Patients with persistent postoperative sagittal imbalance were compared with the sagittally balanced group. We also assessed for threshold values.
  
  
  RESULTS
  Acute PJF was observed in 60 of 173 patients (35%) and was least common in fusions with the UIV in the upper thoracic (UT) spine (p=.035). Of those who developed APJF, 21.7% required surgery. Proximal junctional kyphosis 15° or more was the most common form of APJF in fusions to the UT spine but least likely to need revision (p=.014). The most common mode of failure in lower thoracic (LT) or lumbar (L) fusions was UIV fracture. Postoperative SVA less than 50 mm was a significant risk factor for APJF (p=.009).
  
  
  CONCLUSIONS
  Acute PJF is more common in patients with preoperative sagittal imbalance (35%) than the general adult deformity patient population, and 37% of those with APJF require revision. It is least common when the UIV is in the UT spine, compared with the LT or L spine. Sagittal balance correction to an SVA 50 mm or less was a significant risk factor in patients with preoperative sagittal imbalance.
authors.affiliation: Department of Orthopaedics, University of Utah, 590 Wakara Way Salt Lake City, UT 84108, USA.
authors.forename: Micah W
authors.initials: MW
authors.lastname: Smith
authors.affiliation: Department of Orthopaedics, University of Utah, 590 Wakara Way Salt Lake City, UT 84108, USA.
authors.forename: Prokopis
authors.initials: P
authors.lastname: Annis
authors.affiliation: Department of Orthopaedics, University of Utah, 590 Wakara Way Salt Lake City, UT 84108, USA.
authors.forename: Brandon D
authors.initials: BD
authors.lastname: Lawrence
authors.affiliation: Department of Orthopaedics, University of Utah, 590 Wakara Way Salt Lake City, UT 84108, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Daubs
authors.affiliation: Department of Orthopaedics, University of Utah, 590 Wakara Way Salt Lake City, UT 84108, USA. Electronic address: Darrel.brodke@hsc.utah.edu.
authors.forename: Darrel S
authors.initials: DS
authors.lastname: Brodke
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery*; D008141:Lordosis / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012086:Reoperation / Q000706:statistics & numerical data; D013123:Spinal Fusion / Q000009:adverse effects*
keywords: Acute proximal junctional failure; Adult spinal deformity; Complication; Proximal junctional kyphosis; Sagittal balance; Sagittal imbalance