Intraprosthetic dislocation after a revision hip replacement: a case report

ABSTRACT BACKGROUND: The dual mobility cup (DMC) was initially design in 1974. It was designed to offer additional stability in total hip arthroplasty (THA) and to prevent dislocations. The dissociation of a DMC has been termed an intraprosthetic dislocation (IPD) and is a rare complication. It is defined as separation of the articulation between the polyethylene and head articulation in the DMC. As the utilisation of DMCs in orthopaedic surgery increases, we can expect an increase in this rare complication. We report a case of an IPD in the setting of revision hip arthroplasty in a 72-year-old female. CASE REPORT: The report is on a 72-year-old female patient who underwent revision hip arthroplasty. The articulation utilised was of the dual mobility type. Some eight months later she dislocated her hip. An attempted closed reduction under general anaesthesia with muscle relaxant was unsuccessful. Thereafter she was taken to surgery to perform an open reduction of the hip. Intra-operatively it was found that the dual mobility head had dissociated, with the polyethylene component remaining in the metal liner. A revision of the components was performed. DISCUSSION: We postulate on the mechanisms of dissociation of the dual mobility head. We review the current literature related to IPD and discuss the risk factors associated with this rare complication. CONCLUSION: The diagnosis of IPD is an indication for revision surgery of the DMC. When utilising a DMC, care should be taken to mitigate against the known risk factors for IPD. All dual mobility dislocations should be reduced under general anaesthesia with muscle relaxant Level of evidence: Level 4.. Keywords: intraprosthetic dislocation, dual mobility cup, revision hip arthroplasty