This study was performed to compare the results of bipolar hemiarthroplasty with those of total hip arthroplasty especially with special respect to the periprosthetic osteolysis.

We analyzed 49 cases of bipolar hemiarthroplasty and 32 cases of total hip arthroplasty using cementless Omnifit Microstructured prosthesis with 28mm femoral head for the treatment of avascular necrosis from 1986 to 1992. All cases were followed up more than 5 years. To determine any association with osteolysis, clinical and radiologic results were analyzed by the chi-square test or two-tailed Student's t-test.

In bipolar hemiarthroplasty, osteolysis occurred in 8 cases (16.3%) . Revision was recommanded in 5 cases (10.2%) . In total hip arthroplasty, osteolysis occurred in 16 cases (50.0%). Revision was recommanded in 7 cases (21.9%) . Osteolysis occurred less in bipolar hemiarthroplasty than in total hip arthroplasty (p<0.05). The size of osteolysis in bipolar hemiarthroplasty (4.2cm2) was smaller than in total hip arthroplasty (9.7cm2) (p<0.05) . In total hip arthroplasty, the linear wear rate of polyethylene insert of the cases with osteolysis (0.36mm/year) was higher than that without osteolysis (0.19mm/year) (p<0.05).

The incidence and size of osteolysis are lower in bipolar hemiarthroplasty than in total hip arthroplasty using Omnifit Microstructured component with 28mm femoral head in cementless cases.