title: Change in acetabular version after lumbar pedicle subtraction osteotomy to correct post-operative flat back: EOS® measurements of 38 acetabula.
abstract: BACKGROUND
  Abnormalities in acetabular orientation can promote the development of hip osteoarthritis, femoro-acetabular impingement, or even acetabular cup malposition. The objective of the present study was to determine whether pedicle substraction osteotomy (PSO) to correct sagittal spinal imbalance affected acetabular orientation.
  
  
  OBJECTIVE
  PSO performed to correct sagittal spinal imbalance affects acetabular orientation by changing the pelvic parameters.
  
  
  METHODS
  This was a descriptive study in which two observers measured the acetabular parameters on both sides in 19 patients (38 acetabula) before and after PSO for post-operative flat-back syndrome. Mean time from PSO to post-operative measurements was 19months. Measurements were taken twice at a 2-week interval, on standing images obtained using the EOS(®) imaging system and sterEOS(®) software to obtain 3D reconstructions of synchronised 2D images. Acetabular anteversion and inclination were measured relative to the vertical plane. Mean pre-PSO and post-PSO values were compared using the paired t-test, and P values lower than 0.05 were considered significant. To assess inter-observer and intra-observer reproducibility, we computed the intra-class correlation coefficients (ICCs).
  
  
  RESULTS
  The measurements showed significant acetabular retroversion after PSO, of 7.6° on the right and 6.5° on the left (P<0.001). Acetabular inclination diminished significantly, by 4.5° on the right and 2.5° on the left (P<0.01). Inclination of the anterior pelvic plane decreased by 8.4° (P<0.01). Pelvic incidence was unchanged, whereas sacral slope increased by 10.5° (P<0.001) and pelvic tilt decreased by 10.9° (P<0.001). The ICC was 0.98 for both inter-observer and intra-observer reproducibility.
  
  
  CONCLUSIONS
  Changing the sagittal spinal alignment modifies both the pelvic and the acetabular parameters. PSO significantly increases sacral slope, thus inducing anterior pelvic tilt with significant acetabular retroversion. The measurements obtained using sterEOS(®) showed good inter-observer and intra-observer reproducibility. To our knowledge, this is the first study of changes in acetabular version after PSO.
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France. Electronic address: thibault.masquefa@gmail.com.
authors.forename: T
authors.initials: T
authors.lastname: Masquefa
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: N
authors.initials: N
authors.lastname: Verdier
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: O
authors.initials: O
authors.lastname: Gille
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Boissière
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: I
authors.initials: I
authors.lastname: Obeid
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Maillot
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: C
authors.initials: C
authors.lastname: Tournier
authors.affiliation: Service d'orthopédie traumatologie, hôpital Pellegrin, place Amélie-Raba-Leon, 33076 Bordeaux cedex, France.
authors.forename: T
authors.initials: T
authors.lastname: Fabre
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D060751:Bone Retroversion / Q000000981:diagnostic imaging / Q000209:etiology*; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy; D011183:Postoperative Complications / Q000000981:diagnostic imaging; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013122:Spinal Diseases / Q000209:etiology / Q000601:surgery*
keywords: Acetabular retroversion; Pedicle subtraction osteotomy; Sagittal balance; Total hip arthroplasty; Transpedicular osteotomy