Dislocation following total hip endoprosthesis. Association with surgical approach and other factors

During a period of eight years (1984 to 1992) we found 45 dislocations in 1734 patients treated by total hip arthroplasty. We compared this retrospectively evaluated group with a randomized control group of 61 patients. As a cause for an increasing number of dislocations in 1989 we found: age over 70 years, high CCD-stem-angle (142 degrees), dorsal approach, abduction of the acetabular component under certain circumstances (left side). Revision operations always are a high risk procedure. Acetabular anteversion, anaesthesia, way of component fixation did not induce an increased rate of dislocation. We now left the dorsal approach and use only stems with an CCD-angle of 135 degrees or less by now. Careful positioning of the acetabular components and a better patient-instruction helped to decrease the number of dislocations. Because of these measures we reduced the THA-dislocations rate from 5.6 to 0.17 per cent (first operations) and from 12.1 to 6.5 per cent (revision operations).