In 28 patients with surgically proved loosening of hip-joint endoprostheses and 42 patients without loosening between 2 and 12 years after implantation and without clinical or radiological signs of loosening we performed clinical evaluation, and radiographs, a three-phase bone scan, and a ml t indiumlabeled leukocyte scan (ILLS) The sensitivity of radiographs in the group with loosening of hip-joint endoprostheses in the femoral as well as in the acetabular component was only about 50 %, while the specificity was almost 100 % With a combination of radiographs and ILLS we reached a sensitivity in the acetabular component of 100 % and in the femoral component of 88 %, but specificities of only 57 % in the acetabular component and 40 % in the femoral component were found We found that the ILLS is a very helpful method of examination to detect loosening of hipjoint arthroplasties in doubtful cases.
After infection, the aseptic loosening of an endoprosthesis is the most frequent complication In many cases diagnosis of aseptic loosening of a cemented hip-joint endoprosthesis is very doubtful.
Typical clinical signs and radiological findings are well known, but often they are uncertain and have only a low sensitivity, as indicated in the literature and found among our own patients l 2, 3, 6, 8, 10 l. Typical clinical signs are, e g , the sudden appearance of pain in a hip some years after implantation of an endoprosthesis, pain on movement, particularly in * Professor Dr J Rehn on his 70th birthday Offprint requests to: K W Zilkens, Orthopidische Klinik, Medizinische Falkultat der RWTH,