Background: It is common sense that a hemiarthroplasty for the management of a fracture of neck of femur will inevitably lead to the erosion of the natural acetabulum. Therefore it appears appropriate to confine this treatment to patients with a short life expectancy to spare them the experience of this complication and consequent surgery, whereas younger and healthier patients would have to be offered a Total Hip Replacement for that reason. Occasional clinical experience of amazing longevity of hemiar-throplasties cast doubt on this way of thinking.

Materials and Methods: A series of 699 hemiarthroplasties done in a Swiss orthopaedic department between 1983 to 2003, were studied with regard to revision surgery because of acetabular erosion. In addition to data from the MEM documentation system, acetabular biopsies retrieved on revision surgery were used for this analysis. The incidence of revision surgery for acetabular erosion was statistically compared with the incidence of primary Total Hip Replacement in the Norwegian Hip Register.

Results: The incidence of acetabular erosion following hemiarthroplaty over 20 years in the Swiss series was determined for different age groups. In the most important age group of 70 to 79 years, in this series comprising 249 patients, this incidence was 3,2%. The incidence of Primary Total Hip Replacement for osteoarthritis in the Norwegian Hip Register over 20 years is 3,6% for the same age group.

Conclusion: The incidence of acetabular erosion as a consequence of a hemiarthroplasty was surprisingly low in the Swiss series and did not exceed the incidence of Total Hip Replacement for primary osteoarthritis in a European national population. Acetabular erosion can’t be considered as an inevitable consequence of a hemiarthroplasty, but is to be seen as a complication confined to a certain group of patients.