What factors can lead to nonmodular tapered fluted stem subsidence after revision total hip arthroplasty?

Aim of the study — to evaluate our own experience of the use of non-modular tapered stems in revision hip arthroplasty to determine the incidence and causes of repeated revisions, functional outcomes, and factors associated with subsidence of non-modular tapered stems. Methods. We retrospectively analyzed the results of using 78 non-modular tapered stems. The average follow-up period was 5.1 years. Results. There were repeated revisions accompanied by the removal of non-modular tapered stems in 14 (17.9%) cases. Significant subsidence was observed in 5 (6.4%) cases. Bicortical contact less than 2.0 cm (p = 0.017) was a risk factor for subsidence of non-modular tapered stems. The risk of having a bicortical contact of less than 2 cm was higher in patients with type IV femoral defect (p = 0.048). An improvement in functional parameters was found. Patients with significant subsidence of non-modular tapered stems had worse functional outcomes compared to patients without significant subsidence. Conclusions. The use of non-modular tapered stems in revision hip arthroplasty shows good results in terms of repeated revision rates and functional outcomes. Periprosthetic infection and aseptic loosening were the most frequent causes of repeated revisions with removal of non-modular tapered stems. All patients with significant subsidence of non-modular tapered stems underwent repeated revision due to aseptic loosening. Bicortical contact less than 2.0 cm was a risk factor for significant subsidence of non-modular tapered stems. The risk of bicortical contact less than 2.0 cm was higher in patients with type IV femoral defects. Therefore, it is recommended to use non-modular tapered stems with caution or consider other hip reconstruction options in this type of defect.