[Cup dissociation after reduction of a dislocated hip hemiarthroplasty].

PURPOSE OF THE STUDY: Close reduction of a bipolar hemiarthroplasty dislocation may induce dissociation between the cup and the prosthetic ball head. This rare complication leads to reoperation. CASE REPORT: Two women 84 and 85 years' old suffering from femoral head fracture were treated by bipolar hemiarthroplasty through a postero-lateral approach. After the first post-operative month, a posterior dislocation has occurred. Close reduction, without anesthesia dislocated the intraprosthetic joint. DISCUSSION: Dislocation rate is lower for bipolar hemiarthroplasty than for total hip arthroplasty. Reason for these two dislocation was supposed to be a "bottle-opener" effect's by locking the cup on to the posterior acetabular rim. Limb traction is responsible for intra-prosthetic iatrogenic dislocation.
CONCLUSION: Anesthesia should be considered as necessary for prosthesis bipolar hemiarthroplasties dislocation treatment. The authors have moved to a different implant and modified their surgical approach (antero lateral). These modifications were introduced in order to reduce the rate of hip dislocation and above all the event of intraprosthetic dislocation when close reduction was necessary.