title: Biomechanical evaluation of two types of short-stemmed hip prostheses compared to the trust plate prosthesis by three-dimensional measurement of micromotions.
abstract: BACKGROUND
  Stemless and short-stemmed hip prostheses have been developed to preserve femoral bone stock. While all these prostheses claim a more or less physiological load transfer, clinical long-term results are only available for the stemless thrust plate prosthesis. In this study, the in vitro primary stability of the thrust plate prosthesis was compared to two types of short-stemmed prostheses. In addition to the well-established Mayo prosthesis, the modular Metha prosthesis was tested using cone adapters with 130 degrees and 140 degrees neck-shaft-angles.
  
  
  METHODS
  The prostheses were implanted in composite femurs and loaded dynamically (300-1700 N). Three-dimensional micromotions at the bone-prosthesis interface were measured. In addition, the three-dimensional deformations at the surface of the composite femur were measured to gain data on the strain distribution.
  
  
  RESULTS
  For all tested prostheses, the micromotions did not exceed 150 microm, the critical value for osteointegration. The thrust plate prosthesis revealed similar motions as the short-stemmed prostheses. The short-stemmed prosthesis with the 130 degrees cone tended to have the highest micromotions of all tested short-stemmed prostheses. The thrust plate prosthesis revealed the lowest alteration of bone surface deformation after implantation.
  
  
  CONCLUSIONS
  The comparably low micromotions of the thrust plate prosthesis and the short-stemmed prostheses should be conducive to osseous integration. The higher alteration of load transmission after implantation reveals a higher risk of stress shielding for the short-stemmed prostheses.
authors.affiliation: Department of Orthopaedic Surgery, Grosshadern Medical Center, University of Munich, Marchioninistrasse 15, Munich, Germany. andreas.fottner@med.uni-muenchen.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Fottner
authors.forename: Markus
authors.initials: M
authors.lastname: Schmid
authors.forename: Christof
authors.initials: C
authors.lastname: Birkenmaier
authors.forename: Farhad
authors.initials: F
authors.lastname: Mazoochian
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Plitz
authors.forename: Jansson
authors.initials: J
authors.lastname: Volkmar
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D001860:Bone Plates; D018786:Bone Substitutes; D005269:Femur / Q000473:pathology*; D006801:Humans; D008422:Materials Testing; D011474:Prosthesis Design; D011475:Prosthesis Failure; D019919:Prosthesis Implantation; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D018786:Bone Substitutes