The radiological evaluation of the hip joint after prosthetic arthroplasty of the proximal femur in patients with a tumour using a bipolar femoral head.

Excision of the proximal femur for tumour with prosthetic reconstruction using a bipolar femoral head places a considerable load on the unreplaced acetabulum. We retrospectively reviewed the changes which occur around the affected hip joint by evaluating the post-operative radiographs of 65 consecutive patients who underwent proximal prosthetic arthroplasty of the femur, and in whom an acetabular component had not been used. There were 37 men and 28 women with a mean age of 57.3 years (17 to 93). Radiological assessment included the extent of degenerative change in the acetabulum, heterotopic ossification, and protrusio acetabuli. The mean follow-up was 9.1 years (2 to 11.8). Degenerative changes in the acetabulum were seen in three patients (4.6%), Brooker grade 1 or 2 heterotopic ossification in 17 (26%) and protrusion of the prosthetic head in nine (13.8%). A total of eight patients (12.3%) needed a revision. Five were revised to the same type of prosthesis and three (4.6%) were converted to a total hip arthroplasty. We conclude that radiological evidence of degenerative change, heterotopic ossification and protrusion occur in a few patients who undergo prosthetic arthroplasty of the proximal femur for tumour. The limited extent of these changes and the lack of associated symptoms do not justify the routine arthroplasty of the acetabulum in these patients.