MIGRATION OF THE CHARNLEY STEM IN RHEUMATOID-ARTHRITIS AND OSTEOARTHRITIS - A ROENTGEN STEREOPHOTOGRAMMETRIC STUDY

Migration of 65 Charnley stems implanted with modern cementing techniq ues was studied by roentgen stereophotogrammetry, There were 25 patien ts with rheumatoid arthritis (RA) and 40 with osteoarthritis (OA) foll owed up for two years, In 43 cases a bone sample for histomorphometric analysis was obtained from the femur during the operation. In 22 case s the mean subsidence of the prosthetic head was 0.40 mm and in 20 the mean posterior migration was 1.25 mm. There was no difference in migr ation between the two diagnostic groups (p = 0.8) after adjusting for variations in gender, age and weight, Male gender was associated with increased subsidence (p = 0.006). Histological examination showed that the RA series had more osteoid surface (p = 0.04), but neither this, nor any of the other histomorphometric variables, influenced migration . These results suggest that, unlike the acetabular socket, the cement ed Charnley femoral component is equally secure in osteoarthritis and in rheumatoid arthritis, and that its initial fixation is not influenc ed by the quality of the local cancellous bone, Our results provide da ta with which the early performance of new prosthetic designs and fixa tion methods can be compared.