[Dislocation after total hip arthroplasty]

Dislocations after total hip arthroplasties are one of the most common complications of the procedure. According to registers, recurrent hip dislocations account for up to 30 % of the indications for a revision operation. The incidence of a dislocation is influenced by indication-associated, patient-dependent and operation-specific risk factors. 50 % of the dislocations occur within the first 3 months which confirms the high relevance of operation-specific influencing factors. The diagnosis is almost always made with the help of computed tomography, as this is the only method to determine the three-dimensional relationship of the components. A dynamic fluoroscopic examination can verify an increased translation (reduced soft-tissue tension) and thus enables a functional examination to determine the mechanism of the dislocation. By means of a classification of dislocations into five types under consideration of the implant position, the sufficiency of the pelvitrochantar musculature, the presence of an impingement, the congruence of head and acetabular liner as well as combinations of these factors it is possible to plan an adequate therapy. From the therapeutic point of view the correct positioning of the stem and head is of decisive importance. In addition therapeutic success can be realized by using larger head diameters through to tripolar sockets, reconstruction of soft tissues and, last but not least, an adequate postoperative immobilization. Even so, this treatment is associated with a high rate of complications and in the literature failure rates of up to one third, i.e., the reoccurrence of a dislocation, are reported.