title: Natural history of spinopelvic alignment differs from symptomatic deformity of the spine.
abstract: METHODS
  Cross-sectional study and systematic review of the literature.
  
  
  OBJECTIVE
  Describe the natural history of spinopelvic alignment parameters and their behavior in patients with degenerative spinal deformity.
  
  
  BACKGROUND
  Normal stance and gait requires congruence between the spine-sacrum and pelvis-lower extremities. This is determined by the pelvic incidence (PI), and 2 positional parameters, the pelvic tilt, and sacral slope (SS). The PI also affects lumbar lordosis (LL), a positional parameter. The final goal is to position the body's axis of gravity to minimize muscle activity and energy consumption.
  
  
  METHODS
  Two study cohorts were recruited: 32 healthy teenagers (Risser IV-V) and 54 adult patients with symptomatic spinal deformity. Standing radiographs were used to measure spinopelvic alignment and positional parameters (SS, PI, sacral-femoral distance [SFD], C7-plumbline [C7P], LL, and thoracic kyphosis). Data from comparable groups of asymptomatic individuals were obtained from the literature.
  
  
  RESULTS
  PI increases linearly with age (r2 = 0.8646) and is paralleled by increasing SFD (r2 = 0.8531) but not by SS. Patients with symptomatic deformity have higher SFD (42 +/- 13.6 mm vs. 63.6 +/- 21.6 mm; P < 0.001) and lower SS (42 degrees +/- 9.6 degrees vs. 30.7 degrees +/- 13.6 degrees; P < 0.001) but unchanged PI. The C7P also presents a linear increase throughout life (r2 = 0.8931), and is significantly increased in patients with symptomatic deformity (40 +/- 37 mm vs. 70.3 +/- 59.5 mm; P < 0.001).
  
  
  CONCLUSIONS
  First, Gradual increase in PI is described throughout the lifespan that is paralleled by an increase in SFD, and is not by an increase in the SS. This represents a morphologic change of the pelvis. Second, Patients with symptomatic deformity of the spine present an increased C7P, thoracic hypokyphosis, reduced LL, and signs of pelvic retroversion (decreased LL and SS; increased SFD).
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation, The University of Iowa Hospitals & Clinics, Hawkins Drive, Iowa City, IA 52242, USA. Sergio-mendoza@uiowa.edu
authors.forename: Sergio
authors.initials: S
authors.lastname: Mendoza-Lattes
authors.forename: Zachary
authors.initials: Z
authors.lastname: Ries
authors.forename: Yubo
authors.initials: Y
authors.lastname: Gao
authors.forename: Stuart L
authors.initials: SL
authors.lastname: Weinstein
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D035002:Lower Extremity / Q000098:blood supply*; D008297:Male; D010388:Pelvis / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D011859:Radiography; D012189:Retrospective Studies; D013121:Spinal Curvatures / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D013131:Spine / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*