Is the strain pattern of conventional stems negatively affected by a previously short stem THA? An experimental study in cadavaric bone.

BACKGROUND A short stem hip arthroplasty can be revised in many cases using a conventional stem. Furthermore, in some cases the implantation of a short stem is intended, but intraoperatively reasons may lead to the decision to implant a conventional stem after previous preparation of a short stem. OBJECTIVE In both cases it is questionable if the anchorage of a conventional stem is negatively affected by the previous preparation of a short stem. In clinical practice mid- or long-term follow up for these special cases hardly exist. METHODS The strain patterns for the conventional Bicontact stem in primary implantation and after preparation of the proximal femur for a METHA short stem were tested biomechanically in three pairs of cadaveric femora. RESULTS The strain patterns for the conventional Bicontact after preparation of the METHA short stem were similar to conditions after testing the conventional stem in primary conditions. CONCLUSIONS These data lead to the consequence that in clinical practise the implantation of a conventional stem after preparation of a short stem and even after revision of a short stem is possible without increased risk of loosening or long-term stress-shielding.