title: Ligamentous influence in pelvic load distribution.
abstract: BACKGROUND
  The influence of the posterior pelvic ring ligaments on pelvic stability is poorly understood. Low back pain and sacroiliac joint (SIJ) pain are described being related to these ligaments. Computational approaches involving finite element (FE) modeling may aid to determine their influence. Previous FE models lacked in precise ligament geometries and material properties, which might have influence on the results.
  
  
  OBJECTIVE
  The aim of this study is to investigate ligamentous influence in pelvic stability by means of FE using precise ligament material properties and morphometries.
  
  
  METHODS
  An FE model of the pelvis bones was created from computer tomography, including the pubic symphysis joint (PSJ) and the SIJ. Ligament data were used from 55 body donors: anterior (ASL), interosseous (ISL), and posterior (PSL) sacroiliac ligaments; iliolumbar (IL), inguinal (IN), pubic (PL), sacrospinous (SS), and sacrotuberous (ST) ligaments; and obturator membrane (OM). Stress-strain data were gained from iliotibial tract specimens. A vertical load of 600 N was applied. Pelvic motion related to altered ligament and cartilage stiffness was determined in a range of 50% to 200%. Ligament strain was investigated in the standing and sitting positions.
  
  
  RESULTS
  Tensile and compressive stresses were found at the SIJ and the PSJ. The center of sacral motion was at the level of the second sacral vertebra. At the acetabula and the PSJ, higher ligament and cartilage stiffnesses decrease pelvic motion in the following order: SIJ cartilage>ISL>ST+SS>IL+ASL+PSL. Similar effects were found for the sacrum (SIJ cartilage>ISL>IL+ASL+PSL) but increased ST+SS stiffnesses increased sacral motion. The influence of the IN, OM, and PL was less than 0.1%. Compared with standing, total ligament strain was reduced to 90%. Increased strains were found for the IL, ISL, and PSL.
  
  
  CONCLUSIONS
  Posterior pelvic ring cartilage and ligaments significantly contribute to pelvic stability. Their effects are region- and stiffness dependent. While sitting, load concentrations occur at the IL, ISL, and PSL, which goes in coherence with the clinical findings of these ligaments serving as generators of low back pain.
authors.affiliation: Faculty of Medicine, Institute of Anatomy, University of Leipzig, Liebigstraße 13, 04103 Leipzig, Germany; Department of Trauma and Reconstructive Surgery, Faculty of Medicine, University of Leipzig, Liebigstraße 13, 04103 Leipzig, Germany. Electronic address: niels.hammer@medizin.uni-leipzig.de.
authors.forename: Niels
authors.initials: N
authors.lastname: Hammer
authors.forename: Hanno
authors.initials: H
authors.lastname: Steinke
authors.forename: Uwe
authors.initials: U
authors.lastname: Lingslebe
authors.forename: Ingo
authors.initials: I
authors.lastname: Bechmann
authors.forename: Christoph
authors.initials: C
authors.lastname: Josten
authors.forename: Volker
authors.initials: V
authors.lastname: Slowik
authors.forename: Jörg
authors.initials: J
authors.lastname: Böhme
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D019245:Compressive Strength; D020342:Finite Element Analysis; D006801:Humans; D008022:Ligaments / Q000502:physiology*; D008297:Male; D010388:Pelvis / Q000502:physiology*; D012446:Sacroiliac Joint; D013718:Tensile Strength
keywords: Biomechanics; Finite elements modeling; Iliolumbar ligament; Sacroiliac joint ligaments; Sacrospinous and sacrotuberous ligament