A Study of Bipolar Arthroplasty

we have treated 42 osteoarthritic (OA) and 21 rheumatoid arthritic (RA) hips (mean age: 61) with bipolar arthroplasty (OMNIFIT: 57, OMNIFLEX: 6). In cases with severe bone defects (OA: 13, RA: 12) bone grafting was added to the acetabula. Patients were followed-up for an average of 31 months. Radiological and clinical findings were evaluated for this study. Outer head migration was detected in 46 cases, which stopped within 2 years except for 6 RA cases with bone defects. Stem sinking occured in 46 cases, which stopped within 2 years except for 3 cases. There was no significant correlation between the stem sinking and the canal fit index which were measured immediately after surgery at the levels of the middle and distal stems. No relationship was found between thigh pain and the radiological findings which were characterized by either a radiolucent or sclerotic zone at the distal end of the stem. Special caution should be paid to these RA cases with bone defects who indicate the need for a bipolar arthroplasty. A proximal press fit may be more important than a middle or distal fit in order to prevent stem sinking. Radiological changes at the distal end of the stems may not be the cause of the thigh pain.