title: The effect of aging on deformations of the superficial femoral artery resulting from hip and knee flexion: potential clinical implications.
abstract: OBJECTIVE
  Vessel deformations have been implicated in endoluminal device fractures, and therefore better understanding of these deformations could be valuable for device regulation, evaluation, and design. The purpose of this study is to describe geometric changes of the superficial femoral artery (SFA) resulting from hip and knee flexion in older subjects.
  
  
  METHODS
  The SFAs of seven healthy subjects aged 50-70 years were imaged with magnetic resonance angiography with the legs straight and with hip and knee flexion. From geometric models constructed from these images, axial, twisting, and bending deformations were quantified.
  
  
  RESULTS
  There was greater shortening in the bottom third of the SFA than in the top two thirds (top, 5.9% +/- 3.0%; middle, 6.7% +/- 2.1%; bottom, 8.1% +/- 2.0% [mean +/- SD]; P < .05), significant twist in all sections (top, 1.3 degrees /cm +/- 0.8; middle, 1.8 degrees /cm +/- 1.1; bottom, 2.1 degrees /cm +/- 1.3), and greater curvature increase in the bottom third than in the top two thirds (top, 0.15 cm(-1) +/- 0.06; middle, 0.09 cm(-1) +/- 0.07; bottom, 0.41 cm(-1) +/- 0.22; P < .001).
  
  
  CONCLUSIONS
  The SFA tends to deform more in the bottom third than in the other sections, likely because of less musculoskeletal constraint distal to the adductor canal and vicinity of knee flexion. The SFAs of these older subjects curve off axis with normal joint flexion, probably resulting from known loss of arterial elasticity with age. This slackening of the vessel enables a method for noninvasive quantification of in vivo SFA strain, which may be valuable for treatment planning and device design. In addition, the spatially resolved arterial deformations quantified in this study may be useful for commercial and regulatory device evaluation.
authors.affiliation: Department of Surgery, Stanford University, Clark Center, Room E350, Stanford, CA 94305-5431, USA. cpc@stanford.edu
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cheng
authors.forename: Gilwoo
authors.initials: G
authors.lastname: Choi
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Herfkens
authors.forename: Charles A
authors.initials: CA
authors.lastname: Taylor
mesh_terms: D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D004548:Elasticity; D005263:Femoral Artery / Q000033:anatomy & histology*; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D009119:Muscle Contraction; D054159:Torsion, Mechanical