title: The effect of dynamic femoroacetabular impingement on pubic symphysis motion: a cadaveric study.
abstract: BACKGROUND
  A link between femoroacetabular impingement and athletic pubalgia has been reported clinically. One proposed origin of athletic pubalgia is secondary to repetitive loading of the pubic symphysis, leading to instability and parasymphyseal tendon and ligament injury.                Hypothesis/
  
  
  OBJECTIVE
  The purpose of this study was to investigate the effect of simulated femoral-based femoroacetabular impingement on rotational motion at the pubic symphysis. The authors hypothesize that the presence of a cam lesion leads to increased relative symphyseal motion.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Twelve hips from 6 fresh-frozen human cadaveric pelvises were used to simulate cam-type femoroacetabular impingement. The hips were held in a custom jig and maximally internally rotated at 90° of flexion and neutral adduction. Three-dimensional motion of the pubic symphysis was measured by a motion-tracking system for 2 states: native and simulated cam. Load-displacement plots were generated between the internal rotational torque applied to the hip and the responding motion in 3 anatomic planes of the pubic symphysis.
  
  
  RESULTS
  As the hip was internally rotated, the motion at the pubic symphysis increased proportionally with the degrees of the rotation as well as the applied torque measured at the distal femur for both states. The primary rotation of the symphysis was in the transverse plane and on average accounted for more than 60% of the total rotation. This primary motion caused the anterior aspect of the symphyseal joint to open or widen, whereas the posterior aspect narrowed. At the torque level of 18.0 N·m, the mean transverse rotation in degrees was 0.89° ± 0.35° for the native state and 1.20° ± 0.41° for cam state. The difference between cam and the native groups was statistically significant (P < .03).
  
  
  CONCLUSIONS
  Dynamic femoroacetabular impingement as caused by the presence of a cam lesion causes increased rotational motion at the pubic symphysis.
  
  
  CONCLUSIONS
  Repetitive loading of the symphysis by cam impingement is thought to lead to increased symphyseal motion, which is one possible precursor to athletic pubalgia.
authors.affiliation: Department of Orthopaedic Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA. patrickbirmingham@gmail.com
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Birmingham
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Kelly
authors.forename: Robert
authors.initials: R
authors.lastname: Jacobs
authors.forename: Linda
authors.initials: L
authors.lastname: McGrady
authors.forename: Mei
authors.initials: M
authors.lastname: Wang
mesh_terms: D001696:Biomechanical Phenomena; D005260:Female; D057925:Femoracetabular Impingement / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011631:Pubic Symphysis / Q000503:physiopathology*; D016059:Range of Motion, Articular; D012399:Rotation; D019415:Torque; D016474:Weight-Bearing