Direction of hip arthroplasty dislocation in patients with femoral neck fractures.

In order to prevent hip arthroplasty dislocations, information regarding the direction of the dislocation is important for accurate implant positioning and for optimising the postoperative regimens in relation to the surgical approach used. The aim of this study was to analyse the influence of the surgical approach on the direction of the dislocation in patients treated by a hemiarthroplasty (HA) or total hip arthroplasty (THA) after a femoral neck fracture. Fracture patients have a high risk for dislocations, and this issue has not been previously studied in a selected group of patients with a femoral neck fracture. We analysed the radiographs of the primary dislocation in 74 patients who had sustained a dislocation of their HA (n = 42) or THA (n = 32). In 42 patients an anterolateral (AL) surgical approach was used and in 32 a posterolateral (PL). The surgical approach significantly influenced the direction of dislocation in patients treated with HA (p < 0.001), while no such correlation was found after THA (p = 0.388). For THA patients there was a correlation between the mean angle of anteversion of the acetabular component and the direction of dislocation when comparing patients with anterior and posterior dislocations (p = 0.027). These results suggest that the surgical approach of a HA has an influence on the direction of dislocation, in contrast to THA where the position of the acetabular component seems to be of importance for the direction of dislocation in patients with femoral neck fractures.