title: [Influence of the physiological medium on the mechanical properties of bone cement: can current studies be extrapolated?].
abstract: OBJECTIVE
  The use of bone cement is widespread in orthopaedic surgery. Most of the mechanical tests are performed in dry medium, making it difficult to extrapolate the results. The objective of this study is to assess if the mechanical properties of polymethylmethacrylate (PMMA), obtained in previous reports, are still present in a liquid medium.
  
  
  METHODS
  An experimental study was designed with antibiotic (vancomycin) loaded PMMA. Four groups were defined according to the medium (dry or liquid) and the pre-conditioning in liquid medium (one week or one month). Wear and flexural strength tests were performed according to ASTM and ISO standards. Volumetric wear, friction coefficient, tensile strength, and Young's modulus were analyzed. All samples were examined by scanning electron microscopy.
  
  
  RESULTS
  The samples tested in liquid medium showed lower wear and flexural strength values (P<.05). The kind of wear was modified from abrasive to adhesive in those samples studied in liquid medium. The samples with a pre-conditioning time showed lower values of wear (P<.05).
  
  
  CONCLUSIONS
  Caution is recommended when extrapolating the results of previous PMMA results. The different mechanical strength of the cement in a liquid medium, observed in saline medium, is much closer to the clinical situation.
authors.affiliation: Servicio de Cirugía Ortopédica y Traumatología, Hospital General Universitario Gregorio Marañón, Madrid, España. Electronic address: pablo.sanzruiz@gmail.com.
authors.forename: P
authors.initials: P
authors.lastname: Sanz-Ruiz
authors.affiliation: Instituto para la investigación tecnológica, Departamento de ingeniería mecánica, Universidad Pontificia Comillas, Madrid, España.
authors.forename: E
authors.initials: E
authors.lastname: Paz
authors.affiliation: Grupo desarrollo materiales, Departamento de ingeniería y ciencia de materiales, Universidad Carlos III, Madrid, España.
authors.forename: J
authors.initials: J
authors.lastname: Abenojar
authors.affiliation: Instituto para la investigación tecnológica, Departamento de ingeniería mecánica, Universidad Pontificia Comillas, Madrid, España.
authors.forename: J C
authors.initials: JC
authors.lastname: Del Real
authors.affiliation: Facultad de Medicina, Universidad San Pablo CEU, Madrid, España.
authors.forename: F
authors.initials: F
authors.lastname: Forriol
authors.affiliation: Servicio de Cirugía Ortopédica y Traumatología, Hospital General Universitario Gregorio Marañón, Madrid, España.
authors.forename: J
authors.initials: J
authors.lastname: Vaquero
mesh_terms: D001696:Biomechanical Phenomena; D001843:Bone Cements; D008422:Materials Testing; D019904:Polymethyl Methacrylate
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate
keywords: Antibiotic loaded cement; Bone cement; Cemento con antibiótico; Cemento óseo; Infección protésica; Periprosthetic infection; Polimetilmetacrilato; Polymethylmethacrylate