title: Anthropometric measurements of the femur change with component positioning in total knee arthroplasty.
abstract: BACKGROUND
  To analyze aspect ratio (AP size/ (ML) size) of osteoarthritic knees at four different areas of the femur and to observe if proximalization of the femoral cut would change the ML size as well as confirm that external rotation increases the measurements for the AP dimensions of the femur.
  
  
  METHODS
  From the available MyKnee database (Medacta International, Castel San Pietro, Switzerland) 1030 patients were randomly selected within 20° of deformity consisting of 400 men with a mean (SD) age of 67.5 (9) years and 630 women with a mean (SD) age of 69 (10) years (p<0.0001). A specific software program was developed to measure AP and ML dimensions of the femur on CT-scans for (3D) planning in four areas. The AP femoral size was measured with neutral axial rotation following the epicondylar axis and without accepting anterolateral notching.
  
  
  RESULTS
  Proximalization of the femur resulted in no changes except for a larger ML3 area in men. Increased axial rotation increased the AP dimensions for the same femur by a mean (SD) 2.5 (1) mm for males and females.
  
  
  CONCLUSIONS
  The crucial area for overhang of the femoral component is the anterior region (ML1) with an aspect ratio of about ±, but with an important range. Proximalization of the femoral cut is not accompanied by narrowing of the anterior femur but ML widening of the more posterior femur in men. Increased external rotation leads to a measurement of bigger AP size leading to an AP versus ML mismatch and change in aspect ratio.
authors.affiliation: Cliniques universitaires Saint Luc-UCL, Av. Hippocrate 10, 1200 Brussels, Belgium. Electronic address: emmanuel.thienpont@uclouvain.be.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Thienpont
authors.affiliation: Medacta International SA, Strada Regina, 6874 Castel San Pietro, Switzerland.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Bernardoni
authors.affiliation: Texas Orthopedics, 4700 Seton Center Parkway Suite 200, Austin, 78759 TX, USA.
authors.forename: Tyler
authors.initials: T
authors.lastname: Goldberg
mesh_terms: D000368:Aged; D000886:Anthropometry; D019645:Arthroplasty, Replacement, Knee; D003198:Computer Simulation; D016208:Databases, Factual; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000601:surgery*; D011446:Prospective Studies; D025321:Surgery, Computer-Assisted
keywords: Aspect ratio; Femur; Gender; Sizing; Total knee arthroplasty