Abstract
Wear and osteolysis are the major problems limiting the longevity of total hip arthroplasty. There is general agreement that if left untreated osteolysis will eventually lead to loosening of the acetabular component. In many cases polyethylene liner exchange may be preferable to revision of a well-fixed acetabular component. If there is osteolysis present the question is when should the polyethylene liner exchange be performed? The answer to that question has not been definitively defined at the present time.
There are few studies available that evaluate the timing of surgical intervention when acetabular osteolysis is present. Indications for surgical intervention include prevention of complete wear of the head through the polyethylene liner (liner thickness < 1.5 mm) and when the osteolysis involves 50% or more of the shell circumference on AP or lateral x-rays. Of course persistent pain with wear or osteolysis is another indication for surgery. Contraindications to cup retention and liner exchange include: 1) Malpositioned component; 2) Non-modular component; 3) Unable to obtain hip stability; 4) Thin polyethylene liner (relative); 5) Severe damage to acetabular shell; and 6) Poor track record of the acetabular component.
If one decides to retain the component the following steps are generally involved in operative management. Remove the liner and assess component stability. Assess the locking mechanism for the polyethylene. If the locking mechanism is not intact one can consider cementing the liner in place. In general, it is recommended to debride and bone graft the osteolytic lesion. The author prefers to use an access hole at the periphery of the component or at times a trapdoor can be made in the ilium. It is essential not to de-stabilise the acetabular component. At the present time there is no optimal graft material to use. Potential graft options include demineralised bone matrix or cancellous bone chips. Since dislocation is the number one complication after polyethylene liner exchange, it is a good idea to use a larger femoral head whenever possible. In some cases it is also worthwhile to consider bracing the patient after the surgery.
It is essential to be ready to perform a complete revision. Therefore, when planning to perform a polyethylene liner exchange one needs to have the appropriate components available to completely revise the acetabular component.
