title: Ligamentous contributions to pelvic stability in a rotationally unstable open-book injury: a cadaver study.
abstract: BACKGROUND
  Due to the orientation of the sacroiliac joint (SIJ), as the symphysis widens in an open-book pelvic ring disruption, it should displace inferiorly. The purposes of this study were to reconfirm this inferior displacement and to evaluate the relative contributions of the pubic symphysis (PS), the sacrotuberous/sacrospinous ligament complex (STL/SSL) and the anterior sacroiliac ligament (ASIL) to pelvic ring stability in a rotationally unstable open-book injury.
  
  
  METHODS
  For each of 6 cadaver pelves, the right hemipelvis was fixed to a table and the PS was sectioned. Under fluoroscopy, a manual external rotational force was then applied through the unfixed, left ilium. At the point of maximal displacement, a permanent AP image was obtained. With magnification corrected, horizontal (H) and vertical (V) displacements were measured. The pelves were then divided into two groups of three each. In Group 1, the PS release was followed by sectioning of the STL/SSL, and then the ASIL. In Group 2, the PS release was followed by sectioning of the ASIL and then the STL/SSL. The above described technique of manual manipulation and radiographic measurement was repeated after each stage of ligament release.
  
  
  RESULTS
  The displacement after initial PS sectioning was not significantly different when comparing Group 1 to Group 2. In both groups, a significant and progressive increase in displacement was noted when the PS (H and V; p<0.05) and ASIL (H and V; p<0.05) were sectioned. However, there was no significant change with SSL/STL sectioning in either group. Vertical displacements were all directed inferiorly.
  
  
  CONCLUSIONS
  The PS and ASIL are important in maintaining pelvic ring external rotational stability. However, the SSL/STL has little, if any, effect in this regard. Due to the orientation of the SIJ, external rotation of the hemipelvis, as in open-book injury, will show inferior vertical, as well as horizontal, displacement on the AP radiograph, despite the PSIL being intact.
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University School of Medicine, 3635 Vista Avenue, 7th Floor Desloge Towers, St. Louis, MO 63110, United States.
authors.forename: Adham
authors.initials: A
authors.lastname: Abdelfattah
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University School of Medicine, 3635 Vista Avenue, 7th Floor Desloge Towers, St. Louis, MO 63110, United States. Electronic address: moedbr@slu.edu.
authors.forename: Berton R
authors.initials: BR
authors.lastname: Moed
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D005471:Fluoroscopy; D050723:Fractures, Bone / Q000473:pathology*; D006801:Humans; D007593:Joint Instability / Q000473:pathology / Q000503:physiopathology; D008023:Ligaments, Articular / Q000293:injuries* / Q000473:pathology; D010384:Pelvic Bones / Q000293:injuries* / Q000473:pathology; D011631:Pubic Symphysis / Q000293:injuries* / Q000473:pathology; D012446:Sacroiliac Joint / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology
keywords: Open-book pelvic ring instability; Open-book pelvis injury; Pelvic ligament injury