COMPONENT MOTION IN BIPOLAR HIP-ARTHROPLASTY - AN EVALUATION OF REAMED AND NON-REAMED ACETABULA

Sixty-four patients with 67 bipolar arthroplasties of the hip were rev iewed for a mean follow up of 3.1 years. The study group consisted of 46 hemiarthroplasties secondary to primary osteoarthritis of the hip a nd 21 hemiarthroplasties secondary to displaced subcapital hip fractur es. Reaming of the acetabulum was performed in 47 of the hips studied. The Harris hip scores were not significantly affected by acetabular r eaming. Total motion when hips were loaded in the standing position. R eaming of the acetabulum resulted in a decrease in percent outer compo nent motion and an increase in percent inner component motion. The non -reamed acetabula had the largest percent inner motion decrease when t aken from the supine to the standing position. The reamed acetabula ha d significantly higher average percentage of inner component motion in both standing and supine positions. There was no patient with postope rative acetabular protrusion.