Roentgen stereophotogrammetric analysis and clinical assessment of unipolar versus bipolar hemiarthroplasty for subcapital femur fracture: a randomized prospective study

Abstract

Hemiarthroplasty is a well-established treatment for displaced subcapital fracture, but controversy exists about the optimal implant type. Bipolar hemiarthroplasty has proposed advantages over unipolar hemiarthroplasty in terms of better clinical results and decreased wear of acetabular cartilage. This study is a randomized prospective study of 51 patients (52 hips) receiving either bipolar or unipolar hemiarthroplasty for displaced subcapital fractures. The outcome measurements were clinical scores and Roentgen stereophotogrammetric analysis (RSA) analysis to determine the rate of acetabular wear. Twenty-three patients completed 2-year follow-up. The RSA data demonstrated that there was slightly less acetabular wear by bipolar prostheses than by unipolar. The combined mean three-dimensional wear of the bipolar prostheses was 0.6 mm compared with 1.5 mm for the unipolar prostheses (P= 0.04). The bipolar group generally achieved higher scores in terms of the Harris Hip Score, Western Ontario and McMaster University Index of Osteoarthritis (WOMAC) questionnaire and 6-min walk test. These results were statistically significant at 3 months but not at 12 and 24 months. This study suggests that while the bipolar prosthesis performs slightly better than the unipolar in terms of acetabular cartilage wear and clinical outcomes, it remains debatable whether the benefits are worth the increased cost of the prosthesis.