Abstract
Hip dislocation is one of the most common causes of patient and surgeon dissatisfaction following hip replacement. To correctly treat dislocation, the causes must first be understood.
Patient factors included age greater than 70, medical co-morbidities, female gender, musculo-ligamentous laxity, revision surgery, issues with the abductors and trochanter and education.
Issues related to the surgeon and technique are surgical volume and experience, the surgical approach and repair, adequate restoration of femoral offset and leg length, correct component position, and avoidance of soft tissue or bony impingement.
There are also implant-related factors. Chief among these is the design of the head and neck region. Is the femoral head diameter sufficient, and in concert with the prosthetic neck is there an adequate head-neck ratio? Skirts on longer neck lengths greatly reduce the head-neck ratio and should be avoided if possible. There must be available offset choices in order to restore soft tissue tension. Lipped liners aid in gaining stability, yet if improperly placed may result in impingement and dislocation.
Late dislocation may result from polyethylene wear, soft tissue destruction, trochanteric or abductor disruption and weakness, or infection.
Understanding the causes of hip dislocation allow prevention in a majority of instances. Proper pre-operative planning includes the identification of high-offset patients in whom inadequate restoration of offset will reduce soft tissue tension and abductor efficiency. Component position must be accurate to achieve stability without impingement.
Finally, patient education cannot be over-emphasised, as most dislocations occur early, and are preventable with proper instructions.
