title: Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions: incidence and risk factor analysis of 410 cases.
abstract: METHODS
  Retrospective study.
  
  
  OBJECTIVE
  Determine proximal junctional kyphosis (PJK) prevalence and analyze risk factors associated with PJK in adolescent idiopathic scoliosis (AIS) patients following 3 different posterior segmental spinal instrumentation and fusion surgeries.
  
  
  BACKGROUND
  No comparison study exists on proximal junctional AIS changes following 3 different segmental posterior spinal instrumentation and fusion surgeries at 2 years postoperative.
  
  
  METHODS
  A clinical/radiographic assessment was conducted in 410 consecutive AIS patients (average age = 14.7, range = 10.6-20) (men/women = 73/337) treated with instrumented segmental posterior spinal fusion with 2-year follow-up. Revision and anterior cases were not included. Standing long-cassette radiographic measurements were analyzed including various sagittal/coronal parameters for preoperative, early postoperative, and 2-year follow-up. Abnormal PJK was defined by proximal junction sagittal Cobb angles between the lower endplate of the uppermost instrumented vertebra and the upper endplate of 2 supradjacent vertebrae >or=+10 degrees and at least 10 degrees greater than the preoperative measurement at 2 years postoperative.
  
  
  RESULTS
  PJK prevalence defined at 2 years postoperative was 27% (111 of 410 patients). Statistically significant factors: larger preoperative thoracic kyphosis angle (T5-T12 >40 degrees vs. T5-T12 10 degrees -40 degrees vs. T5-T12 <10 degrees ; P < 0.0001), greater immediate postoperative thoracic kyphosis angle decrease (decrease >5 degrees vs. 5 degrees decrease-5 degrees increase vs. increase >5 degrees ; P < 0.0001), thoracoplasty versus no thoracoplasty (P = 0.001), and men versus women (P = 0.007). Instrumentation types (hook-only vs. proximal hook, distal pedicle screw vs. pedicle screw P = 0.058), number of fused vertebrae >12 versus 12>or= (P = 0.12), the uppermost instrumented vertebra among T2, T3, T4, T5 (P = 0.75). There were no significant differences in Scoliosis Research Society Patient Questionnaire-24 outcome-scores (PJK total score = 97.0, self-image subscales = 21.3 vs. non-PJK group = 95.3, 21.0) (P = 0.34 total score, P = 0.54 self-image subscale).
  
  
  CONCLUSIONS
  Two-year postoperative PJK prevalence in AIS following 3 different posterior segmental spinal instrumentation and fusion surgeries was 27%. A larger preoperative thoracic kyphosis angle, greater immediate postoperative thoracic kyphosis angle decrease, thoracoplasty, and male sex correlated significantly with PJK. There were no significant differences in Scoliosis Research Society Patient Questionnaire-24 outcome-scores between the PJK and non-PJK group.
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine and Shriners Hospitals for Children, St. Louis Unit, St. Louis, Missouri, USA.
authors.forename: Yongjung J
authors.initials: YJ
authors.lastname: Kim
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.forename: Keith H
authors.initials: KH
authors.lastname: Bridwell
authors.forename: Junghoon
authors.initials: J
authors.lastname: Kim
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Cho
authors.forename: Gene
authors.initials: G
authors.lastname: Cheh
authors.forename: Joonyoung
authors.initials: J
authors.lastname: Yoon
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D006801:Humans; D015994:Incidence; D007738:Kyphosis / Q000453:epidemiology*; D008297:Male; D011183:Postoperative Complications / Q000453:epidemiology*; D015995:Prevalence; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000601:surgery*; D012720:Severity of Illness Index; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D013905:Thoracoplasty / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D016896:Treatment Outcome