Rheological Behavior of Different Calf Sera before, during and after Biomechanical Testing
Maximilian Uhler,
Mareike Schonhoff,
Timo A. Nees,
Tanja Wonerow,
Jens Nuppnau,
Frank Mantwill,
Jan Philippe Kretzer,
Stefan Schroeder
Affiliations
Maximilian Uhler
Laboratory of Biomechanics and Implant Research, Department of Orthopaedics, Heidelberg University Hospital, Schlierbacher Landstraße 200a, 69118 Heidelberg, Germany
Mareike Schonhoff
Laboratory of Biomechanics and Implant Research, Department of Orthopaedics, Heidelberg University Hospital, Schlierbacher Landstraße 200a, 69118 Heidelberg, Germany
Timo A. Nees
Department of Orthopaedics, Heidelberg University Hospital, 69118 Heidelberg, Germany
Tanja Wonerow
Department of Mechanical Engineering, Machine Elements and Computer-Aided Product Development, Helmut-Schmidt-University, 22043 Hamburg, Germany
Jens Nuppnau
Department of Mechanical Engineering, Machine Elements and Computer-Aided Product Development, Helmut-Schmidt-University, 22043 Hamburg, Germany
Frank Mantwill
Department of Mechanical Engineering, Machine Elements and Computer-Aided Product Development, Helmut-Schmidt-University, 22043 Hamburg, Germany
Jan Philippe Kretzer
Laboratory of Biomechanics and Implant Research, Department of Orthopaedics, Heidelberg University Hospital, Schlierbacher Landstraße 200a, 69118 Heidelberg, Germany
Stefan Schroeder
Laboratory of Biomechanics and Implant Research, Department of Orthopaedics, Heidelberg University Hospital, Schlierbacher Landstraße 200a, 69118 Heidelberg, Germany
Due to different rheological behavior of human synovial fluid and the test mediums for in vitro examinations, wear tests cannot replicate the in vivo situation completely. The standards for wear testing indicate calf serum as in vitro test medium. However, these standards do not contain precise information on the main constituent components and the rheological properties. In this study, bovine calf serum and newborn calf serum with a protein concentration of 20 g/L, both approved for wear testing defined by the International Organization for Standardization (ISO), were characterized according to their rheological properties to detect differences before and during tribological simulation. The rheological behavior was determined at five defined intervals of a tribological test. The two test fluids differ in their rheological properties before and during the test and can therefore lead to deviating results in tribological testing. Furthermore, both test media changes considerably over test duration. At a test duration of 0.5 Mio cycles, both fluids have changed so that there is no longer any difference between them in terms of rheological properties. These changes could be attributed to denaturation and degradation of proteins. Thus, the choice of medium impacts tribological test results which should be considered for the interpretation of these studies.
