title: Primary stability in cementless femoral stems: custom-made versus conventional femoral prosthesis.
abstract: OBJECTIVE
  To compare a custom-made femoral stem with a conventional cementless stem for initial stability in human femurs.
  
  
  METHODS
  The bone-femoral prosthesis interface motion was measured in vitro using displacement transducers. Combined axial and torsional loads simulating single-leg stance, loading were applied.
  
  
  BACKGROUND
  The custom-made prosthesis is a cementless femoral stem fabricated from the patient's CT-reconstruction. To justify its clinical use its design has to be tested regarding his primary stability.
  
  
  METHODS
  Seven pairs of human cadaveric femurs were used for testing the custom-made prosthesis versus a conventional cementless stem. Subsidence, rotation and interface motion were measured with load cycles up to 2000 N.
  
  
  RESULTS
  The critical interface motion of 150 microm for the cementless prosthesis was not exceed for both types of prosthesis. The custom-made prosthesis enlarged in its metaphyseal part showed a decrease of dynamic micromotions and rotation behavior in the proximal region compared to the Alloclassic prosthesis stem.
  
  
  CONCLUSIONS
  The initial stability of the custom-made femoral stem was comparable to that of a conventional femoral stem.
  
  
  CONCLUSIONS
  The data set for initial stability justifies the clinical use of a custom-made femoral stem in primary hip replacement. An individualized stem fit into the endosteal cortical bone decrease micromotion.
authors.affiliation: Department of Orthopaedics, University Hospital of Muenster, Albert-Schweitzer-Str. 33, D-48129 Muenster, Germany. chrgoetze@uni-muenster.de
authors.forename: Christian
authors.initials: C
authors.lastname: Götze
authors.forename: Wolfram
authors.initials: W
authors.lastname: Steens
authors.forename: Volker
authors.initials: V
authors.lastname: Vieth
authors.forename: Christopher
authors.initials: C
authors.lastname: Poremba
authors.forename: Lutz
authors.initials: L
authors.lastname: Claes
authors.forename: Jörn
authors.initials: J
authors.lastname: Steinbeck
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D001843:Bone Cements; D002102:Cadaver; D002484:Cementation / Q000379:methods*; D005260:Female; D005269:Femur / Q000503:physiopathology / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011336:Probability; D011474:Prosthesis Design; D017755:Prosthesis Fitting; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D014159:Transducers; D016474:Weight-Bearing
chemical_list: D001843:Bone Cements