Risk factors for radiological changes after bipolar hemiarthroplasty for osteonecrosis of the femoral head.

OBJECTIVES

This study aimed to report the mid-term radiological outcomes of patients with bipolar hemiarthroplasty (BHA) for stage 3 osteonecrosis of the femoral head (ONFH), and to identify the risk factors for postoperative radiological changes.

METHODS

We retrospectively investigated 62 patients (38 men and 24 women; mean age, 50.1 years) aged <70 years who underwent primary BHA for Association Research Circulation Osseous stage 3 ONFH between 1998 and 2010. The mean follow-up period after BHA was 12.8 years. The following changes were assessed on follow-up radiographs: outer head migration, polyethylene wear, and femoral osteolysis. The association between demographic data and the development of postoperative radiological changes was evaluated.

RESULTS

Radiological changes were found in 20 hips (32.3%) at a mean of 8.1 years after BHA; of these, three hips (4.8%) underwent total hip arthroplasty conversion at a mean of 10.9 years after BHA. Both univariate and multivariate analysis revealed that younger age and female sex were independent risk factors for the development of postoperative radiological changes.

CONCLUSION

The current results suggest that the indication of BHA should be carefully determined in young or female patients with ONFH, even when the disease is in the early stage.