title: Are the left and right proximal femurs symmetric?
abstract: BACKGROUND
  The contralateral femur frequently is used for preoperative templating for THA or hemiarthroplasty when the proximal femur is deformed by degenerative changes or fracture. Although femoral symmetry is assumed in these situations, it is unclear to what degree the contralateral femur is symmetrical.
  
  
  OBJECTIVE
  We therefore defined the degree of asymmetry between left and right proximal femurs and determined whether it was affected by demographics and proximal femoral anatomy.
  
  
  METHODS
  We obtained 160 paired femurs from individuals (20-40 years old), evenly distributed for gender and ethnicity (African-American and Caucasian). The height and weight of the individuals were recorded. We measured the femoral head diameter, minimal femoral neck diameter in the AP and cephalocaudal (CC) planes, and the AP femoral diaphyseal diameter. The absolute and percent differences were determined.
  
  
  RESULTS
  All femoral measurements showed an absolute difference less than 2 mm and a percent asymmetry and difference less than 2% for the femoral head, less than 4% for the femoral neck, and less than 3.5% for the femoral shaft. We found no correlation or predictive value between absolute differences and asymmetry and age, ethnicity, gender, or weight. Height was negatively associated with femoral head differences and thus increased symmetry of the femoral head.
  
  
  CONCLUSIONS
  Our data support assumptions of substantial symmetry of the proximal femur and highlights that asymmetry is not affected by demographics or the size of the proximal femur. Asymmetry tends not to occur in isolated segments of the femur.
authors.affiliation: Department of Orthopaedics, Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, 11100 Euclid Ave., Cleveland, OH 44106, USA. ernest.young.81@gmail.com
authors.forename: Ernest Y
authors.initials: EY
authors.lastname: Young
authors.forename: Jeremy
authors.initials: J
authors.lastname: Gebhart
authors.forename: Daniel
authors.initials: D
authors.lastname: Cooperman
authors.forename: Nicholas U
authors.initials: NU
authors.lastname: Ahn
mesh_terms: D000328:Adult; D001741:Black or African American; D001827:Body Height; D001835:Body Weight; D002102:Cadaver; D005260:Female; D005269:Femur / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005270:Femur Head / Q000033:anatomy & histology; D005272:Femur Neck / Q000033:anatomy & histology; D006801:Humans; D016014:Linear Models; D008297:Male; D011859:Radiography; D044465:White People; D055815:Young Adult