Instability after Total Hip Replacement

Instability after total hip replacement is a major cause of patient morbidity, second only to aseptic loosening of the components. Many factors, including surgical approach, implant design, soft tissue integrity, patient compliance, and experience of the surgeon, play an important role in the etiology of hip dislocation. An understanding of the timing, mechanism, and direction of the instability helps in formulating a treatment plan whether surgical or nonoperative. Radiographic evaluation, especially component orientation, restoration of offset, and leg length, can give valuable information about any abnormal biomechanics of the dislocated hip. Initial treatment of postoperative hip dislocation may not require surgery, but recurrent dislocation with an identifiable cause is best managed surgically. Revision hip surgery for recurrent instability can be a challenging problem. A better understanding of the etiology and the use of constrained liners at many centers have shown improved results with surgical management. Patients should be counseled regarding realistic expectations before revision surgery for recurrent dislocations. As a result of the greater emphasis paid to meticulous capsule repair, orientation of the components, and soft tissue tension, the incidence of instability after a primary hip arthroplasty is extremely low.