Analysis of the acetabular migration profile in rheumatoid arthritis compared with cementless acetabular revision

In a retrospective analysis the migration profile of 73 cementless total hip implants (Zweymuller Alloclassic) in 54 patients with rheumatoid arthritis were compared with the results of 58 implants of the same design in 50 patients undergoing cementless revision after loosening of an Endler cup. 258 conventional radiographs of the rheumatoid patients and 164 radiographs of the revision group were digitized. The migration analysis was performed using a modified Dickob's technique that allows for correction of different X-ray magnifications as well as horizontal and vertical tilting of the pelvis. The analysis of migration exceeded 2 mm in eight rheumatoid patients. In three of them clinical loosening of the acetabular cup was obvious. In the group of patients after cup revision a significantly higher amount of cranial migration was detected compared with the rheumatoid patients. This phenomenon could be explained by the destruction of the weight-bearing cranial acetabular sclerosis after reaming.