title: Pelvic lordosis and alignment in spondylolisthesis.
abstract: OBJECTIVE
  Pelvic morphology and lumbopelvic lordosis were measured on standing radiographs of 75 patients with greater than 10% L5-S1 spondylolytic spondylolisthesis. The findings were compared with those of 75 volunteers to determine significant differences between the two groups.
  
  
  BACKGROUND
  Etiology of isthmic (lytic) spondylolisthesis remains uncertain. Causation appears to be multifactorial. The relationship between pelvic morphology and spondylolisthesis deserves additional study.
  
  
  METHODS
  Both groups had a standing lateral radiograph of the thoracolumbar spine and pelvis taken that included both hips. Three radiographic angles for pelvic morphology (pelvisacral, pelvic incidence, and pelvic lordosis) were measured by two observers. Each offered similar reliability. Measurement of the pelvic lordosis angle by the pelvic radius technique required fewer steps. It also allowed calculation of the combined angles comprising both the pelvic morphology component for lordosis (the constant pelvic lordosis angle) and the lordosis in the lumbar spine (the variable lumbar lordosis from T12-S1) that should complement the fixed pelvic lordosis (the complementary lumbopelvic lordosis). Mean values and statistical correlations were then computed for each group and compared.
  
  
  RESULTS
  The mean slippage for patients was 30% (range, 11-85%), with 34 patients (45%) having Grade I slips, 32 (43%) having Grade II slips, and nine (12%) having Grade III and IV slips. The mean measurements between patients and volunteers were significantly different (P < 0.01) for lumbar lordosis, pelvic lordosis, and lumbopelvic lordosis. Subgroups of patients with increasingly larger slips (Grade I-III) had significantly smaller mean angles for pelvic lordosis.
  
  
  CONCLUSIONS
  The pelvic and lumbopelvic parameters studied were different in patients compared with controls. The contribution of the pelvis to lordosis was significantly smaller in the subgroups of patients with increasingly larger grades of spondylolisthesis. Pelvic morphology may play a role in the development of spondylolisthesis. Measurement of the combined lumbar and pelvic (lumbopelvic) lordosis on standing radiographs is important.
authors.affiliation: Spine Surgery Service, North Kansas City Hospital, North Kansas City, Missouri, USA. rogerjackson@attglobal.net
authors.forename: Roger P
authors.initials: RP
authors.lastname: Jackson
authors.forename: Timothy
authors.initials: T
authors.lastname: Phipps
authors.forename: Chris
authors.initials: C
authors.lastname: Hales
authors.forename: Jim
authors.initials: J
authors.lastname: Surber
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008141:Lordosis / Q000145:classification / Q000150:complications / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010384:Pelvic Bones / Q000000981:diagnostic imaging*; D011859:Radiography; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012447:Sacrum / Q000000981:diagnostic imaging; D013131:Spine / Q000000981:diagnostic imaging*; D013168:Spondylolisthesis / Q000150:complications / Q000000981:diagnostic imaging*; D009626:Terminology as Topic