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.

The uncemented cup with iliac stem ensures immediate primary stability by fixation to the hipbone in acetabular loosening with severe bone defect. Homologous bone grafts contribute to restoring bone stock, which is a fundamental requirement for long lasting implant stability. From 2002 to 2004 we implanted 23 cups with iliac stems in 22 patients. In 7 cases there was also stem loosening, and so total hip arthroplasty was performed. In 2 patients the defect was grade 2b, in 5 grade 3a, and in 16 grade 3b according to Paprosky. A direct lateral approach was performed in the supine position. Morselized bone grafts were used in all cases by the “impaction grafting” technique, and in 4 cases modelled structural grafts were also employed. Mean follow-up has been 18 months (8–32). So far we have not had any cases of loosening. At follow-up x-rays showed remodelling of the grafts with integration. The cup with iliac stem enables primary stability on healthy bone tissue, and protects the grafts form mechanical stimulation, thus allowing them to integrate and restore bone-stock. It also restores the centre of rotation, and provides functional benefits and implant stability

Aim: The objective of this study was to compare the initial stability of an uncemented curved long stem femoral component (ABR, Zimmer, Warsaw Indiana) implanted using conventional broaching to an uncemented ABR implanted as a revision using morselized compacted allograft to fill a circumferential proximal bone defect. Materials and Methods: Primary: Eight fresh frozen human femurs were implanted with correctly sized ABR stems without cement using standard surgical instruments and 1mm distal overreaming. The implant was loaded cyclically at 3 hz on a MTS servohdraulic materials test frame in a direction representing the peak force of the stance phase of the gait (2.5 X body weight). A 3-dimensional motion measurement device with six linear variable transformers measure the relative motion between the bone and the prosthesis with an accuracy of 0.5μm. The contruct was loaded in ten cycle increments until the component was seated and then recoverable motion was recorded over a further ten loading cycles. Revision: In the revision case bone loss was modelled by removing all the cancellous bone from the proximal femur with 1mm distal overreaming. Morselized bone graft was impacted into the defect using specially prepared smooth tamps shaped to the geometry of the ABR stem. The original prosthesis was then reimplanted without the use of cement. The seating and testing cycles were repeated. Primary and revision vectors were compared using a paired students t – test. Results: There was no statistically significant difference in the magnitude of the resultant vector of the 3 translational components of the micro motion between the two methods of implantation (p=0.19). Conclusions: Initial stability of a cementless femoral implant is a requirement for bone ingrowth. The use of compacted morsellized allograft in a revision Total Hip Arthroplasty with a proximal circumferential defect can provide a stable bed for the implantation of an uncemented femoral component. The revised implant using the compacted allograft method was initially as stable as the primary implantation. This technique would be particularly applicable when the surgeon would like to avoid the use of cement in a revision setting. The use of this method for uncemented revision Total Hip Arthroplasty should be studied further in a clinical setting before it is advocated for widespread use