LOOSENING OF THREADED ACETABULAR COMPONENTS - RADIOGRAPHIC MANIFESTATIONS

Radiographic signs of loosening were assessed, and their sequential ap pearance recorded, in a retrospective analysis of 20 loosened, threade d acetabular cups. There was radiographic evidence of loosening in 19 (95%) cups. In decreasing order of frequency, the radiographic manifes tations included bone resorption between the threads in 19 (95%) cups, increased bone density above the cup in 15 (75%), continuous lucency around the cup in 14 (70%), axial migration in 9 (45%), and rotation i n 6 (30%). The order of appearance of these radiographic manifestation s was the same as the order of frequency of occurrence of the alterati ons. In the one patient with no radiographically detectable signs of l oosening, the cup did not move freely but was easily detached during s urgery. Early radiographic diagnosis of loosening requires accurate po sitioning of the patient in order for the radiographs to reveal bone r esorption between the threads of the cup.