[Loosening of hip prostheses in chronic rheumatoid polyarthritis].
The hip with rheumatoid arthritis (RA) is characterized by reduced bone resistance. Protrusion, fatigue fractures and femoral head collapse are the typical consequences. The survival rate of total hip prostheses in hips with RA seems to be higher than for hips with osteoarthritis (OA), possibly due to lower demands. When isolated loosening of the acetabular and femoral component are compared, there is a definite shift towards acetabular loosening in RA compared to OA. This is definitely due to the reduction in the mentioned bone resistance at the acetabular level. In primary joint replacement, well-cemented femoral components provide more reliable clinical results. They will remain the gold standard for long-term performance as well. On the other hand, it is very likely that non-cemented acetabular components, fixed by means of screws in the direction of the resulting force or based on a compression principle, may prove at least as effective as well-cemented acetabuli. For revision of the loose acetabular component, the use of special metal rings fixed with screws and bridging severe bony defects with a bone graft and frequently also bone cement, have proved to be of value. For loose femoral components with a thin and brittle cortical wall, special non-cemented prostheses combined with a bone graft seem to promise a more reliable long-term solution than cemented versions. The follow-up of our revision cases confirms the value of the described methods - at least at the short and medium-term follow-up. More definite conclusions can only be arrived at after long-term follow-ups which have been carried out with different systems and where the results are compared using the same documentation procedure.