Radiophosphate evaluation of loose hip prostheses

There were 23 patients who had revisions of their failed hip arthroplasties and a prior radiophosphate assessment of the joint components. In this selected group of patients the true positive incidence of abnormal scintigraphic findings for femoral component loosening was 19 out of 20 (95%) and the true negative incidence was two out of two by the criteria adopted. The true positive incidence of such findings, indicating acetabular component loosening, was seven out of seven, and the true negative was nine out of 10. Some of these patients also had contrast arthrography and the incidences of true positive and true negative findings for femoral component loosening were seven out of 15 (47%) and one out of one, respectively. Prediction of the status of the acetabulum was poorer using this technique with true positive and true negative incidences of four out of nine and two out of five, respectively.