title: Does pelvic width influence patellar tracking? A radiological comparison between sexes.
abstract: BACKGROUND
  Pelvic width has been believed to affect patellar tracking by influencing the quadriceps angle (Q-angle). Anatomically, the upper arm of the Q-angle does not closely match the orientation of the quadriceps femoris. The pelvis is often considered wider and the Q-angle larger in female than in male individuals. The purpose of this retrospective study was to investigate the accuracy of such an assumption by using a radiologic comparison, which might be more objective.
  
  
  METHODS
  One hundred consecutive adult patients (50 men and 50 women) aged 18-30 years with unilateral injury to the lower extremity were studied. Full-length standing X-rays of these patients was used to analyze the relationship between the pelvis and the uninjured lower extremity and compare it between the sexes. The pelvic width was defined as the distance between the centers of the bilateral femoral heads.
  
  
  RESULTS
  The pelvic width did not differ statistically between male and female (P=0.74). The femur length and sum of the lengths of the femur and tibia differed between the sexes (both P<0.001). Normalization of the pelvic width to the femur length or sum of the lengths of the femur and tibia resulted in a significant difference between male and female (P<0.001). The angle formed by the femoral and tibial mechanical axes correlated strongly with the angle formed by the femoral anatomic and tibial mechanical axes (Pearson correlation coefficient=0.89).
  
  
  CONCLUSIONS
  Pelvic width does not differ with respect to gender. The pelvis may appear relatively wider in women due to the difference in body height. However, this difference may not increase Q-angle. Patellar mal-tracking may stem from other, more critical predisposing factors.
  
  
  METHODS
  Level IV. Anatomic study.
authors: Department of Orthopedic Surgery, Chang Gung Memorial Hospital, Chang Gung University, Kweishan, Taoyuan, Taiwan. Electronic address: ccwu@mail.cgu.edu.tw.
authors: C-C
authors: CC
authors: Wu
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D010329:Patella / Q000000981:diagnostic imaging* / Q000502:physiology*; D010388:Pelvis / Q000000981:diagnostic imaging / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011859:Radiography; D012189:Retrospective Studies; D055815:Young Adult
keywords: Anatomic axis; Mechanical axis; Patellar tracking; Pelvic width; Q-angle