Abstract
Introduction
Since 1981, we have used various types of the total hip prosthesis for the reconstruction of the acetabular protrusion in rheumatoid arthritis. The cemented Charnley prosthesis was used during the initial 8 years, and we experienced loosening of the cemented acetabular socket in some cases. The bipolar femoral head prosthesis, which started to be used from 1984, was one of the cementless prosthesis. And it showed high frequency of proximal migration of outerhead. The threaded socket also showed frequent loosening. To overcome these problems, we started to utilize a new method from 1988. This method included packing morselized bone grafts into the acetabulum and fix them using a porous coated socket and screws. This study describes the results of cementless total hip arthroplasty (THA) for the acetabular protrusion in rheumatoid arthritiswith this method.
Materials and methods
Sixty -one cementless THAs with use of porous coated acetabular socket were performed in 50 patients who had sever protruded acetabulum due to rheumatoid arthritis. The average follow –up period was 9 years and 5 months (range, 5 to 13 years). A Mallory/ Head prosthesis with porous coated socket was used in 43 hips and other types in 18 hips. In all operated hips, autogenous morselized bones were grafted on the thin acetabullar wall.
Results
The clinical improvement in pain was the most apparent. X-ray findings of the grafted bone in the acetabulum showed a homogenous pattern in most cases (90. 2%) at 6 months after the operation. A radiolucent zone at a non-weight-bearing area between the grafted bone and socket was seen in 20 hips (32. 7%) for 3 years after the operation, and it gradually disappeared and changed to a sclerotic zone. Collapse and /or absorption of the grafted bone were noted in 3 hips of the patients with sever osteoporosis and high disease activity.
Discussion
There are several technical key points to succeed THA in patients with rheumatoid arthritis. The first is the selection of the acetabular socket. The second is the method of bone grafting, and the third is the size and the shape of grafted bones. We have used various types of prosthesis for the protruded acetabulum so far, and it was considered that the bipolar and threaded types are not acceptable because of their high frequency of proximal migration and loosening. The mass and /or block bone should not be used, because they are liable to fall into collapse. It is safely recommended to use slice or morselized bones to lead the grafts to early survival and remodelling caused by tight and close contacts.
Conclusion
THA with the use of morselized bone grafting into the acetabulum and a fixation with a porous coated socket-and screws is a simple and useful procedure for treating protruded acetabulum in rheumatoid arthritis.
