title: Difference in femoral head and neck material properties between osteoarthritis and osteoporosis.
abstract: BACKGROUND
  Osteoarthritis and osteoporosis are the two most common musculoskeletal diseases found in the aged population. It is of interest to measure and study the material properties of the femoral head and neck of these two groups, and hopefully to offer explanation of the observed phenomenon that most patients suffer from one of the two disorders, not both.
  
  
  METHODS
  Seven osteoarthritic and seven osteoporotic femoral heads were used for this study. The principal compressive region of the femoral heads were cut to determine the Young's modulus and yielding stress by a material testing machine. Comparisons between these two groups were conducted by using material properties and the properties normalized by individual patient physical parameters, including body weight, body height and femoral head diameter, respectively. The finite element model of femoral neck cuboid in OA and OP were obtained based on the micro-CT-scan cross-section. The intrinsic material properties were calculated from the solid FE models.
  
  
  RESULTS
  The results showed significant differences in density, modulus and strength between the osteoarthritic and osteoporotic femoral heads as measured, with the former having 2-3 times the values of the latter. Femoral head diameter has stronger influence in mechanical properties than patient's body weight and body height. Regarding to bone volume (BV), bone surface (BS), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and true trabecular elastic modulus, the intrinsic material properties of femoral neck with OA were higher than OP.
  
  
  CONCLUSIONS
  It is still unknown why patients do not suffer from both osteoporosis and osteoarthritis at the same time. Many studies aimed to investigate the mechanical property of two groups. However, individual difference of the femoral head and neck is too difficult to obtain a reasonable comparison between these two groups. This study investigated the two groups more quantitatively and further estimated the factors which influence mechanical properties from a biomechanical point of view.
authors.affiliation: Department of Orthopedics and Traumatology, Lotung St. Mary's Hospital, I-Lan, Taiwan.
authors.forename: Shih-Sheng
authors.initials: SS
authors.lastname: Sun
authors.forename: Hsiao-Li
authors.initials: HL
authors.lastname: Ma
authors.forename: Chien-Lin
authors.initials: CL
authors.lastname: Liu
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Huang
authors.forename: Cheng-Kung
authors.initials: CK
authors.lastname: Cheng
authors.forename: Hung-Wen
authors.initials: HW
authors.lastname: Wei
mesh_terms: D000368:Aged; D019245:Compressive Strength; D003198:Computer Simulation; D004548:Elasticity; D005260:Female; D005270:Femur Head / Q000503:physiopathology*; D005272:Femur Neck / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D010003:Osteoarthritis / Q000503:physiopathology*; D010024:Osteoporosis / Q000503:physiopathology*; D013314:Stress, Mechanical