title: The Quadriceps Vector is Most Parallel to the Spherical Axis With Minimal Difference for Gender or Ethnicity.
abstract: The extensor mechanism may be the key to kinematic alignment of total knee arthroplasty. The purpose of this study was to determine any differences in the direction of the quadriceps vector based on gender or ethnicity and to determine which anatomically derived alignment axis is closest to the quadriceps vector.
  
  
  
  Computed tomography scans and patient records for 14 Caucasians (9 men and 5 women) and 40 Japanese (19 men and 21 women) were evaluated. Three axes of alignment-anatomic, mechanical, and spherical-were identified, measured, and compared to the quadriceps vector in each case. Principal component analysis was used to determine the quadriceps vector by using 3-dimensional models of muscles on computed tomography scans.
  
  
  
  No statistically significant differences in the orientation of the quadriceps vector were found based on gender or ethnicity, and the quadriceps vector was most closely aligned with the spherical axis.
  
  
  
  Because the quadriceps is the primary knee extensor, the spherical axis therefore may be a ubiquitous guide to alignment of the arthroplasty knee based on motion.
authors.affiliation: Department of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan; Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan; Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Mochizuki
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: J David
authors.initials: JD
authors.lastname: Blaha
authors.affiliation: Department of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Tanifuji
authors.affiliation: Center for Fostering Innovative Leadership, Institute for Research Collaboration and Promotion, Niigata University, Niigata, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Kai
authors.affiliation: Department of Orthopaedic Surgery, Niigata Medical Center, Niigata, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan; Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamagiwa
mesh_terms: D000293:Adolescent; D000328:Adult; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D044466:Asian People; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007564:Japan; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008953:Models, Anatomic; D025341:Principal Component Analysis; D052097:Quadriceps Muscle / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D044465:White People; D055815:Young Adult
keywords: 3-dimensional quadriceps vector; ethnicity; precision; principal component analysis; reproducibility; total knee arthroplasty