title: Traction force needed to reproduce physiologically observed uterine movement: technique development, feasibility assessment, and preliminary findings.
abstract: OBJECTIVE
  This study aimed to describe a novel strategy to determine the traction forces needed to reproduce physiologic uterine displacement in women with and without prolapse.
  
  
  METHODS
  Participants underwent dynamic stress magnetic resonance imaging (MRI) testing as part of a study examining apical uterine support. Physiologic uterine displacement was determined by analyzing uterine location in images taken at rest and at maximal Valsalva. Force-displacement curves were calculated based on intraoperative cervical traction testing. The intraoperative force required to achieve the uterine displacement measured during MRI was then estimated from these curves. Women were categorized into three groups based on pelvic organ support: group 1 (normal apical and vaginal support), group 2 (normal apical support but vaginal prolapse present), and group 3 (apical prolapse).
  
  
  RESULTS
  Data from 19 women were analyzed: five in group 1, five in group 2, and nine in group 3. Groups were similar in terms of age, body mass index (BMI), and parity. Median operating room (OR) force required for uterine displacement measured during MRI was 0.8 N [interquartile range (IQR) 0.62-3.22], and apical ligament stiffness determined using MRI uterine displacement was 0.04 N/mm (IQR 0.02-0.08); differences between groups were nonsignificant. Uterine locations determined at rest and during maximal traction were lower in the OR compared with MRI in all groups.
  
  
  CONCLUSIONS
  Using this investigative strategy, we determined that only 0.8 N of traction force in the OR was required to achieve maximal physiologic uterine displacement seen during dynamic (maximal Valsalva) MRI testing, regardless of the presence or absence of prolapse.
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan, L4000 Women's Hospital, 1500 E. Medical Center Dr., SPC 5276, Ann Arbor, MI, 48109-5276, USA. scarolyn@med.umich.edu.
authors.forename: Carolyn W
authors.initials: CW
authors.lastname: Swenson
authors.affiliation: Department of Mechanical Engineering, University of Michigan, L4000 Women's Hospital, 1500 E. Medical Center Dr., SPC 5276, Ann Arbor, MI, 48109-5276, USA.
authors.forename: Jiajia
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Biomedical Engineering, University of Michigan, L4000 Women's Hospital, 1500 E. Medical Center Dr., SPC 5276, Ann Arbor, MI, 48109-5276, USA.
authors.forename: Luyun
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Mechanical Engineering, University of Michigan, L4000 Women's Hospital, 1500 E. Medical Center Dr., SPC 5276, Ann Arbor, MI, 48109-5276, USA.|Department of Biomedical Engineering, University of Michigan, L4000 Women's Hospital, 1500 E. Medical Center Dr., SPC 5276, Ann Arbor, MI, 48109-5276, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Ashton-Miller
authors.affiliation: Department of Obstetrics and Gynecology, University of Michigan, L4000 Women's Hospital, 1500 E. Medical Center Dr., SPC 5276, Ann Arbor, MI, 48109-5276, USA.
authors.forename: John O L
authors.initials: JO
authors.lastname: DeLancey
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005240:Feasibility Studies; D005260:Female; D013509:Gynecologic Surgical Procedures / Q000379:methods*; D006801:Humans; D008022:Ligaments / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D014143:Traction; D014596:Uterine Prolapse / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D014599:Uterus / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D014636:Valsalva Maneuver
keywords: Apical support; Prolapse; Uterine movement