Classification and treatment of dislocations of total hip arthroplasty.

A review of 39 dislocations of total hip arthroplasties revealed three causes: positional (Type I); soft tissue imbalance (Type II); and component malposition (Type III). Forty-one percent of hips had a single dislocation, and 59% had multiple dislocations. Reoperation was performed in 42%, with 28%, mostly Type III problems, requiring revision; all had had multiple dislocations. Forty percent of the dislocations resulted in complications that were primarily the result of bedrest for treatment. Based on the cause of dislocation, to reduce complication, component positions are determined by roentgenographic analysis. Positional dislocations (the patient assumes a position that exceeds the mechanical stability of the prosthesis) are treated by four to six weeks' use of the hip brace, which limits flexion and adduction. Soft tissue imbalance, most often a result of failure of fixation of the greater trochanter or an excessive femoral neck cut, can be treated initially by a brace. If recurrent dislocations occur, reattachment of the trochanter and/or revision to a long-neck prosthesis should be considered. Component position errors were successfully treated without revision only if a single acetabular error was present. If the acetabulum is malpositioned in two planes or severe retroversion of the femoral component is present, immediate revision is advisable.