Kenneth Raymond St John

Orthopedic Surgery, Higher Education, Bioengineering



  • Kenneth R. St John · Robert A. Poggie
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    ABSTRACT: Using an eight-station hip wear simulator, radiation-crosslinked polyethylenes were tested for their resistance to wear-related weight loss and the results compared to results for studies conducted on the same machine using polyethylene that was being implanted at the time. The testing results showed that the wear rate of crosslinked (60 kGy) Slab Compression Molded (SCM) polymer was about 63% lower than standard (30 kGy) SCM cups and 69% less than Ram Extruded 4150 (30 kGy) cups. The Near-net Final Shape molded (NFS) crosslinked (60 kGy) specimens had an 89% reduction in wear rate over the standard (30 kGy) NFS cups, regardless of whether GUR 1020 or GUR 1050 crosslinked cups were tested. All wear rates for nitrogen packaged materials were significantly superior to those for cups sterilized in air and for earlier generation GUR 4150 products sterilized and stored in contact with oxygen. The results confirm that both the SCM and NFS molding processes produce acetabular cups with excellent wear properties as compared to previous processes. The additional crosslinking process, described herein, provided a major improvement in the wear resistance with either molding process with greater improvement occurring in the NFS specimens.
    No preview · Book · Jan 2004
  • Kenneth Raymond St. John
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    ABSTRACT: This volume contains 19 papers from the conference proceedings. Some of the topics discussed by the papers are here cited as examples: debris-mediated osteolysis--a cascade phenomenon involving motion, wear, particulates, macrophage induction, and bone lysis; clinical and experimental studies in the biology of aseptic loosening of joint arthoplasties and the role of polymer particles; histopathological effects of ultrahigh-molecular-weight polyethylene and metal wear debris in porous and cemented surface replacements; endosteal osteolysis around well-fixed porous-coated cementless femolar components; failure mechanism of a metal-backed patella: an implant retrieval study; histomorphological reaction patterns of the bone to diverse particulate implant materials in man and experimental animals; a comparison of the biocompatibility of polymethyl methacrylate debris with and without titanium debris: a comparison of two in vivo models; in vivo activation of monocyte macrophages and fibroblasts by metal particles; and human plasma adsorption to particulate arthroplastic component materials in vitro.
    No preview · Book · Jan 1992

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