[Why does a total hip replacement dislocate? : Diagnosis and management].

Background: Dislocations represent one of the leading complications and the most common cause of early surgical revision in primary total hip arthroplasty (THA). Patient-, implant- and procedure-related factors can contribute causally by impairing soft tissue tension and/or impingement-free mobility.

Influencing factors: Patient-specific factors, such as underlying neurological disorders or reduced spinopelvic mobility, should be carefully considered by the surgeon when selecting implants and devising a treatment strategy. Furthermore, the range of market-approved implants offers a broad spectrum of preventive measures for dislocation in both primary and revision settings.

Therapy: Central to prevention is the precise and appropriate positioning of the implant, tailored to the patient's individual joint biomechanics. While tripolar acetabular systems are utilized in specific patient groups during primary surgery and revision procedures, constrained liners, should be reserved as a fallback strategy in exceptional cases. The occurrence of a THA dislocation constitutes a medical emergency, necessitating immediate radiographic evaluation and early reduction. In cases of a first-time dislocation, additional imaging may be warranted during follow-up, whereas recurrent dislocations mandate tomographic imaging to exclude malpositioning or loosening of the implant. This review summarizes the underlying causes and preventive strategies for THA instability, as well as the diagnostic and therapeutic algorithms for managing THA dislocations.