title: The Impact of Total Hip Arthroplasty on Pelvic Motion and Functional Component Position is Highly Variable.
abstract: This study's purpose was to determine the impact of THA implantation on pelvic motion, and to assess motion in patients with a history of lumbar fusion or prosthetic dislocation.
  
  
  
  This was an IRB-approved, prospective investigation of 3 cohorts: (1) patients without a history of lumbar surgery undergoing THA (group A), (2) patients with a lumbar fusion (group B), and (3) patients with a THA prosthetic dislocation (group C). All patients received both standing and sitting lateral pelvis images to measure sacral slope and pelvic tilt in the sagittal plane.
  
  
  
  Fifty-eight patients were enrolled (24 group A, 27 group B, and 7 group C), with no differences in age, gender, or body mass index (P = .1-.7). In group A, the mean change in sacral slope from standing to sitting was 22.1° ± 15.2° preoperatively and 19.5° ± 14.8° postoperatively. However, in 13 patients, the difference in pelvic motion from the standing to seated position, from preoperatively to postoperatively, was >5° and in 10 patients, this difference was >10°. The change in standing to sitting sacral slope was significantly less in patients with a lumbar fusion (9.8° ± 8.2°) and history of prosthetic dislocation (12.5° ± 4.7°) vs group A (P < .001 and P = .008).
  
  
  
  Implantation of a THA can increase or decrease sagittal plane pelvic motion from the standing to seated position with a high degree of variability. Thus, the ability to predict ideal component positioning from preoperative images may be challenging.
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, Illinois.
authors.forename: Denis
authors.initials: D
authors.lastname: Nam
authors.affiliation: Department of Orthopedic Surgery, Washington University School of Medicine/Barnes-Jewish Hospital, St. Louis, Missouri.
authors.forename: Venessa
authors.initials: V
authors.lastname: Riegler
authors.affiliation: Department of Orthopedic Surgery, Washington University School of Medicine/Barnes-Jewish Hospital, St. Louis, Missouri.
authors.forename: John C
authors.initials: JC
authors.lastname: Clohisy
authors.affiliation: Department of Orthopedic Surgery, Washington University School of Medicine/Barnes-Jewish Hospital, St. Louis, Missouri.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Nunley
authors.affiliation: Department of Orthopedic Surgery, Washington University School of Medicine/Barnes-Jewish Hospital, St. Louis, Missouri.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Barrack
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009038:Motion; D056888:Patient Positioning; D010384:Pelvic Bones / Q000502:physiology*; D010388:Pelvis; D011184:Postoperative Period; D011187:Posture; D011446:Prospective Studies; D016059:Range of Motion, Articular; D012447:Sacrum; D013123:Spinal Fusion
keywords: dislocation; functional position; pelvic motion; sagittal plane; total hip arthroplasty