3-PHASE BONE-SCINTIGRAPHY PATTERN OF LOOSENING IN UNCEMENTED HIP PROSTHESES

The three-phase bone scintigraphy pattern of loosening in uncemented h ip prostheses (UHPs) has not previously been elucidated. We evaluated 28 patients with complicated UHPs who had undergone total hip arthropl asty a very long time previously (range 3-20 years, mean 8.4). All the patients were surgically reviewed: 26 UHPs were found to be loosened and two infected. Nine asymptomatic UHPs were taken as controls, The d ynamic phase was invariably negative in both loosened and asymptomatic UHPs while markedly positive in the infected ones. The blood pool pha se was positive to various degrees in 16 of the 26 loosened UHPs as we ll as in the infected UHPs, but was invariably negative in painless re placements, In the bone phase, areas of significantly (discrete to mar ked) increased uptake were observed in all the loosened prostheses as well as in two-thirds of the asymptomatic ones, However, the regions o f the lesser trochanter and/or tip and/or shaft were involved exclusiv ely in the case of the loosened UHPs, and diffuse periprosthetic uptak e was found only with loosened or infected implants. Areas of slight m ethylene diphosphonate (MDP) uptake were found at every periprosthetic site and areas of discrete to marked MDP uptake were commonly found i n the acetabulum and/or the greater trochanter with both loosened and painless prostheses and are thus considered to be nonspecific findings .