title: The geometry of the trochlear groove.
abstract: BACKGROUND
  In the natural and prosthetic knees the position, shape, and orientation of the trochlea groove are three of the key determinants of function and dysfunction, yet the rules governing these three features remain elusive.
  
  
  OBJECTIVE
  The aim was to define the three-dimensional geometry of the femoral trochlea and its relation to the tibiofemoral joint in terms of angles and distances.
  
  
  METHODS
  Forty CT scans of femurs of healthy patients were analyzed using custom-designed imaging software. After aligning the femur using various axes, the locations and orientations of the groove and the trochlear axis were examined in relation to the conventional axes of the femur.
  
  
  RESULTS
  The trochlear groove was circular and positioned laterally in relation to the mechanical, anatomic, and transcondylar axes of the femur; it was not aligned with any of these axes. We have defined the trochlear axis as a line joining the centers of two spheres fitted to the trochlear surfaces lateral and medial to the trochlear groove. When viewed after aligning the femur to this new axis, the trochlear groove appeared more linear than when other methods of orientation were used.
  
  
  CONCLUSIONS
  Our study shows the importance of reliable femoral orientation when reporting the shape of the trochlear groove.
authors.affiliation: Division of Surgery, Oncology, Reproductive Biology and Anaesthetics, Department of Musculoskeletal Surgery, Imperial College London, 7th Floor, Charing Cross Hospital, London, UK. f.iranpour@imperial.ac.uk
authors.forename: Farhad
authors.initials: F
authors.lastname: Iranpour
authors.forename: Azhar M
authors.initials: AM
authors.lastname: Merican
authors.forename: Wael
authors.initials: W
authors.lastname: Dandachli
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Amis
authors.forename: Justin P
authors.initials: JP
authors.lastname: Cobb
mesh_terms: D005269:Femur / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D008875:Middle Aged; D010329:Patella / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D011859:Radiography; D013977:Tibia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging