As is probably the case with all successful innovations, the unique
design of the thrust plate prosthesis (TPP) was not born of a sudden
fancy for a radically different hip joint replacement, but emerged from
elaborate biomechanical investigations on the loosening of conventional,
intramedullarly anchored hip prosthesis shafts. In the 1970s, hip
revisions due to loosening of the prostheses became a burden to patients
not only physically and psychologically but also economically. This
meant that it also became a matter of daily concern to the orthopaedic
surgeon, who then had to cope with new, previously unknown problems.
Loosening processes were de- tected within 5 years of implantation in up
to 25% of cases. While implant loosenings were considered to be the
result of incorrect handling of materials, we felt that a number of
details still had to be considered in regard to the behavior of the
entire bone-prosthesis complex and the action of mechanical forces.