[Diagnostics and therapy of luxation after total hip arthroplasty]

Luxation following endoprosthetic hip replacement represents a frequent and severe complication and is the reason for a relevant number of hip arthroplasty revision interventions. The probability of occurrence of luxation of a total hip arthroplasty is associated with the indications, patient and operation-specific risk factors. Approximately 50 % of luxations after total hip arthroplasty occur within 3 months of the operation (early luxation).

The diagnostics of luxation of total hip arthroplasty are carried out by clinical and radiological methods. The causative assignment is made by assessment of joint stability, the bony situation (e.g. loosening, periprosthetic fracture and defects) and the soft tissue (e.g. pelvitrochanterian musculature). In cases of clinical and paraclinical signs of infection and of late luxations, a joint puncture is indicated.

Therapy decisions are made depending on the cause (e.g. implant malpositioning, pelvitrochanterian insufficiency, impingement, incongruence between head and inlay and combinations of causes). Therapy of acute total hip prosthesis luxation begins with imaging controlled repositioning carried out with the patient under adequate analgesia and sedation. Conservative therapy is carried out by immobilization with a hip joint orthesis or pelvis-leg cast for 6 weeks. Operative therapy strategies for recurrent luxation are restoration of the correct implant position and sufficient soft tissue tension. Larger hip heads, bipolar heads and tripolar cups are more commonly used due to the geometrically lower probability of dislocation (higher jumping distance). Luxation of total hip prostheses due to infection is treated according to the principles of periprosthetic infection therapy. The rate of recurrence of luxation of 30 % is high so that in cases of unsuccessful therapy treatment should best be carried out in a center for revision arthroplasty.

The search for the exact cause of total hip prosthesis luxation is extremely important. A classification is only possible when the exact cause is known and together with patient and implant-specific details the therapeutic approach can be ascertained. In revision operations the intraoperative functional diagnostics must be exactly documented. The reasons for delayed luxations could be prosthesis infections, abrasion and loosening.