Difficult complications after hip joint replacement. Dislocation.

Dislocation after hip replacement occurs at an overall incidence of 2% to 3% and has significant cost and morbidity implications. Statistically increased incidence is observed in females and in the elderly, and after reoperation procedures. Specific causes include cup malrotation, trochanteric migration, and decreased femoral offset. Head size, leg length, and postoperative mobilization have not proven to be causative factors, but the posterior exposure statistically and consistently is associated with increased instability. Extended acetabular walls do lessen the incidence of dislocation in the primary but even more significantly in the revision procedure. Early (< 3 months) dislocations successfully are treated by 4 to 8 weeks of immobilization in 60% to 70% of instances. The most successful reoperations are those in which the specific cause of the dislocation has been defined. The success rate is approximately 80% for cup reorientation and trochanteric advancement. Nonspecific or ill defined causes are managed successfully by surgical intervention in only approximately 50% of cases. With extensive soft tissue compromise, limited experience with certain salvage options include the bipolar implant with a reported success rate of approximately 80%. Captive articular designs also seem to be successful in approximately 70% of instances but with relatively short term followup and lingering concerns regarding the long term integrity of the fixation.