Dissociation of modular total hip arthroplasty at the femoral head-neck interface after loosening of the acetabular shell following hip dislocation

Modular component dissociation is a potential problem of current modular to tal hip arthroplasty (THA) systems. We describe a case of dissociation of t he modular THA at the femoral head-neck inter-face after loosening of the a cetabular shell during closed reduction for posterior dislocation of THA. T he causes of this dissociation and acetabular shell loosening are discussed . Successful treatment was provided with surgical revision of the acetabula r and the femoral head components. The present case serves as a graphic rem inder that the acetabular shell overhanging the acetabular bone must be avo ided when implanting modular THA components. Key words: total hip arthropla sty, dislocation, femoral head-neck dissociation, acetabular shell loosenin g, surgical revision.