Modular femoral head dissociation after dislocation and entrapment in reconstruction ring: a case report.

Dissociation of modular components is an infrequent potential complication characteristically unique to modularity. We present a patient in whom dissociation of the modular femoral head occurred at attempted closed reduction after dislocation, with the intraoperative findings including entrapment of the head between the rim of a reconstruction ring and the acetabular bone. In the case a dislocation in a patient that was previously reconstructed with a reinforcement ring and a modular femoral stem occurs, dissociation of the modular head should be considered as an extremely uncommon complication that does not outweigh the advantages given by modularity.