Improvement of the long-term adhesive strength between metal stem and polymethylmethacrylate bone cement by a silica/silane interlayer system

A loss of adhesive strength between metal stem and bone cement is clinicall y found to be a serious problem in total hip arthroplasty and causes many o perative revisions. The objective of this study was to improve the longterm adhesive strength at this interface. A new silica/silane interlayer coatin g system is introduced. The layers are designed to bond the metal stem surf ace to the polymethylmethacrylate bone cement marginally leakage free. hi v itro tensile tests were performed on specimens of TiA16V4 and CoCrMo that w ere cemented by pairs with different bone cements with and without the new coating system. The specimens were stored in isotonic saline solution up to 150 days. The adhesive strength decreased about 75% within 30 days of stor age on specimens of both metal alloys that were conventionally cemented wit hout the new interlayer system. With the new coating, the high initial adhe sive strength (40-50 MPa) could be stabilized for TiAl6V4 over 150 days. Fo r the same 150-day storage period, the adhesive strength of the coated CoCr Mo alloy still decreased but the decrease was only half that experienced by the uncoated CoCrMo. The loss of adhesive strength on CoCrMo specimens cou ld be reduced if the metal surface was activated by a plasma treatment. The new coating interface system could help to considerably reduce revision op erations caused by debonding effects at the interface metal/polymethylmetha crylate bone cement. (C) 2001 John Wiley & Sons, Inc.