With cementless porous-coated acetabular replacements, extensive bone loss can occur without effecting implant stability. As a result, the surgeon is frequently faced with re-operating on a well-fixed cementless acetabular component with osteolysis and must decide whether or not to remove a well-fixed porous coated socket. A classification system and treatment algorithm has been developed to aid in management decisions regarding re-operation for polyethylene wear and pelvic osteolysis. Cases are classified into one of 3 possible categories depending on the radiographic stability of the porous coated shell and the ability to replace the polyethylene liner. Type I case; stable porous coated shell, liner replaceable; Type II case; socket stable, liner not replaceable;. Type III case; socket loose, not osseointegrated. Treatment Algorithms - Retain well-fixed shell in Type I cases and replace the liner. Debride accessible lytic lesions and graft with allograft chips. Remove the well-fixed shell in Type II case. Assess defect once the shell is removed. Reconstruction based on the bony defect present. The vast majority can be revised with a larger porous coated socket. Remove loose socket in Type III cases. Assess defect and reconstruct based on the defect. There is a greater need for more extensive grafting and the use of reconstruction rings with Type III cases. This treatment algorithm has helped the authors successfully evaluate and treat a large series of patients with polyethylene wear and pelvic osteolysis in association with porous coated acetabular components. The stability of the acetabular component and appropriate knowledge of the implant are important factors that impact surgical management

With cementless porous-coated acetabular replacements, extensive bone loss can occur without affecting implant stability. As a result, the surgeon is frequently faced with re-operating on a well-fixed cementless acetabular component with osteolysis and must decide whether or not to remove a well-fixed porous coated socket. A classification system and treatment algorithm has been developed to aid in management decisions regarding re-operation for polyethylene wear and pelvic osteolysis. Cases are classified into one of 3 possible categories depending on the radiographic stability of the porous coated shell and the ability to replace the polyethylene liner. Type I case; stable porous coated shell, liner replaceable; Type II case; socket stable, liner not replaceable; Type III case; socket loose, not osseointegrated. Relative Contra-indications for Liner Exchange – Type II Case - Malpositioned socket, Severely damaged shell or lock detail (consider cementing shell in place), Poor track record of the implant, Highly crosslinked polyethylene liner of adequate thickness not available, Ongrowth (as opposed to ingrowth) fixation surface. Treatment Algorithm. Type I Case: Retain well-fixed shell in Type I cases and replace the liner. Debride accessible lytic lesions and graft with allograft chips. Type II Case: Remove the well-fixed shell in Type II case. Assess defect once the shell is removed. Reconstruction based on the bony defect present. The vast majority can be revised with a larger porous coated socket. Type III Case: Remove loose socket. Assess defect and reconstruct based on the defect. There is a greater need for more extensive grafting and the use of reconstruction rings with Type III cases. This treatment algorithm has helped the authors successfully evaluate and treat a large series of patients with polyethylene wear and pelvic osteolysis in association with porous coated acetabular components. The stability of the acetabular component and appropriate knowledge of the implant are important factors that impact surgical management

Introduction and Aims: The purpose of the present study was to review the early results and clinical performance of FDA approved large unipolar heads (36mm and greater) used with a metal-on-metal (MM) bearing. Method: Fourteen stem type prostheses were implanted in 14 patients. There were eight primary THA, and six conversions of surface arthroplasties in which thin-walled (5mm) porous coated MM sockets were maintained. Mean age was 55.4 years (range 30–72 years). There were nine males and five females. Dislocation precautions were discontinued after capsular healing (six weeks). The initial etiology was OA in 78%. Results: The median head size was 44mm (36–52) and socket size 54mm. Mean follow-up time was 29.1 months (range 12–81). UCLA hip scores improved for pain, walking, function, and activity from 4.8, 6.2, 6.1, and 4.8 pre-operatively to 9.3, 8.5, 7.5, and 5.4 postoperatively. Range of motion normalised. There were no complications. Conclusion: This investigation shows excellent clinical results, and suggests that dislocation can be avoided by an anatomical THR with the use of large unipolar femoral heads and thin sockets with low wear bearings. The advantage of MM is the ability to manufacture thin shells with porous beads for fixation and preserve ace-tabular bone stock

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