title: Migration and strains induced by different designs of force-closed stems for THA.
abstract: OBJECTIVE
  Subtle differences in stem design can result in different mechanical responses of the total hip arthroplasty. Tests measuring migration of the stem relative to the femur, as well as the strains in the cement mantle and on the femur can detect different mechanical behavior between stems.
  
  
  METHODS
  In this article, conical, double and triple tapered stems were implanted in composite femurs and subjected to static and cyclic loads. Stems differed mainly on taper angle, calcar radius and proximal stiffness. Stem migration and strains on the femur and in the cement mantle were achieved.
  
  
  RESULTS
  Significant differences (p < 0.05) were noted in the permanent rotation between double and triple tapers, in the strains on the proximal medial femur between triple and both conical and double tapers, and in the strains on the lateral proximal femur between double tapers and both conical and triple tapers.
  
  
  CONCLUSIONS
  The proposed mechanical tests were able to detect significant differences in the behavior of these resembling stems. Stem proximal stiffness and the calcar radius of the stem influence its rotational stability and the strain transmission to the femur.
authors.affiliation: Post-graduate Program in Materials Science and Engineering, Universidade Federal de Sergipe (UFS), São Cristóvão, SE, Brazil.
authors.forename: Sandro
authors.initials: S
authors.lastname: Griza
authors.affiliation: Centro de Estudos do Serviço de Cirurgia e Reabilitação Ortopédica e Traumatológica, Batatais, SP, Brazil.
authors.forename: Luiz Sérgio Marcelino
authors.initials: LS
authors.lastname: Gomes
authors.affiliation: Universidade Luterana do Brasil (Ulbra), Canoas, RS, Brazil.
authors.forename: André
authors.initials: A
authors.lastname: Cervieri
authors.affiliation: Post-graduate Program in Metallurgical Engineering, de Minas e de Materiais, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil.
authors.forename: Telmo Roberto
authors.initials: TR
authors.lastname: Strohaecker
keywords: Hip arthroplasty; Mechanical phenomena; Prosthesis design