title: The effect of interspinous implant surgery on back surface shape and radiographic lumbar curvature.
abstract: BACKGROUND
  Interspinous process implants, used to augment lumbar spine surgery, putatively induce a local segmental lumbar kyphosis yet few investigations outline the effect in vivo on thoracolumbar sagittal curvature. Changes in lumbar skeletal alignment and posture have traditionally relied upon radiographic and back surface spinal curvature measurements, respectively.
  
  
  METHODS
  Lumbar lordosis curvature in 10 healthy subjects (6F, 4M; mean age 36 years) and 10 interspinous implant lumbar surgery patients (5F, 5M; mean age 51 years) was assessed with rasterstereography at baseline and at 6 weeks. Skeletal lumbar lordosis in standing was measured from lateral erect radiography pre- and 6 weeks post-operatively in the surgical cohort, and compared to angulation obtained for surface lordosis curvature derived from rasterstereography.
  
  
  RESULTS
  Repeatable measurement of standing lumbar lordosis from rasterstereographic back shape imaging in healthy volunteers and lumbar surgery cases was demonstrated. Reductions of 0.6 (NS) in healthy and 3.1 (significant, P<0.001) in surgical subjects were recorded for surface lumbar lordosis angle between the 6 week time-points. Slight flattening of the segmental angle and regional lordosis after DIAM surgery was revealed by radiography. Skeletal and surface lumbar lordosis changes were uncorrelated preoperatively (rho=0.28) and postoperatively (rho=0.26).
  
  
  CONCLUSIONS
  Rasterstereography is sensitive in assessing lumbar lordosis changes in healthy and lumbar surgical individuals over time. Surgery with DIAM for lumbar pathology may result in an initial mild flattening of lordosis. Serial investigations of spinal curvature after surgery with DIAM interspinous implant are warranted in order to better understand the time-course of spinal posture changes of such cases.
authors.affiliation: Centre for Musculoskeletal Studies, School of Surgery, The University of Western Australia, Royal Perth Hospital, MRF Building, Rear 50 Murray St, Perth, Western Australia 6000, Australia. crawfr04@student.uwa.edu.au
authors.forename: R J
authors.initials: RJ
authors.lastname: Crawford
authors.forename: R I
authors.initials: RI
authors.lastname: Price
authors.forename: K P
authors.initials: KP
authors.lastname: Singer
mesh_terms: D000328:Adult; D001415:Back / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*; D008297:Male; D008953:Models, Anatomic; D019736:Prostheses and Implants / Q000009:adverse effects*; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity