OSTEOLYSIS AROUND UNCEMENTED ACETABULAR COMPONENTS OF COBALT-CHROME SURFACE REPLACEMENT HIP-ARTHROPLASTY

Ten cases of major osteolysis were identified in patients with hemisph erical cobalt chrome acetabular components of cementless resurfacing t otal hip prostheses at follow-up examinations ranging from two to five years. All components were porous coated with cobalt chrome spheres a nd were stabilized initially with screws. Five patients were women and five were men, with ages ranging from 20 to 59 years. The radiolucent cystic lesions with peripheral rims of reactive bone formation appear ed one to five years after the operation. They measured from 1.5 to 6 cm in the largest diameter and were most often found adjacent to the s crews used to secure the acetabular components to the skeleton. On the radiographs, none of the components appeared to be loose. Three patie nts had revision surgery. In two of the three cases, the implants were found to be firmly fixed. There was no clinical or bacteriologic evid ence of infection. The polyethylene articulating surface showed signs of wear in all three cases and in one of the three it dislocated from the metal shell. Granulation tissue was found in the regions of osteol ysis, and the diseased tissue contained numerous macrophages and giant cells. Lymphocytes and plasma cells were rare. Numerous small particl es of phagocytosed polyethylene and metal in the cells were noted in t wo casts, whereas only polyethylene was found in the third. The cases presented in this report show that major osteolysis can occur around c ementless acetabular components of surface replacement arthroplasty, a nd is most likely related to the contamination of tissue with particle s of the implant materials either from wear or corrosion resulting in a foreign-body reaction to the particulate materials. The high inciden ce of acetabular osteolysis (ten of 25) with the use of this cementles s surface replacement arthroplasty suggests that the presence of polye thylene may be the more important of the two.