Die Biegestabprothese: ein experimenteller Ansatz zur metaphysären Hüftendoprothetik

The aim of our study was to develop a femoral component for total
hip arthroplasty that would exclusively anchor in the metaphysis of
the femoral neck. To forego trochanteric fixation, the load needs
to be transferred to the metaphysis at as many points as possible.
A computer simulation model suggested that an implant with a
central cylinder and 16 rods aligned along a thread would be the
preferable solution. To evaluate primary implantation stability, 14
fresh frozen cadaver femora were used. A special instrument set was
developed to allow for centered implantation of the prosthesis
without the need to dissect the greater trochanter. For our tests,
we used two prototype implants: one made from titanium and the
other from a CoCrMo alloy. For the measurement of micromotions at
the medial proximal femur, sinusoid dynamic loading with a force
between 300 N and 1700 N and a frequency of 1 Hz was employed. In a
neutral position of 16 degrees adduction and 9 degrees
ante-torsion, the average micronnotions measured were 119 mu m.
Despite these convincing in vitro results with regards to primary
stability, circular cut-out of the implant, followed by aseptic
osteonecrosis, loosening might still occur in a clinical situation.
Animal experiments are therefore required to further evaluate this
new implant design.