[Bone dynamic study--evaluation for factor analysis of hip joint].

Factor analysis was applied to dynamic study of Tc-99m MDP for the evaluation of hip joint disorders. Fifteen patients were examined; eight were normal, six were osteoarthritis in which one accompanied synovitis was included, and one was aseptic necrosis on the head of the femur. In normals, according to the Tc-99m MDP kinetics, three factor images and time-activity curves were obtained which were named as blood vessel, soft tissue, and bone factor images and curves. In the patient with osteoarthritis, increased accumulation of the hip joint was shown in bone factor image only. But in one patient, who took osteoarthritis with synovitis, marked accumulations of the Tc-99m MDP appeared not only on the bone factor image but also on the soft tissue. Operation revealed thickening synovial tissue around the hip joint, caused by inflammatory process. In follow-up studies of the patient with aseptic necrosis on the head of the left femur, excessive accumulations, which were seemed in his left hip joint on both bone and soft tissue factor images at first, were decreased respondently to the treatment of this lesion. In conclusion, the factor analysis was useful for differencial diagnosis of the hip joint disorders and observation of the clinical course of the hip joint disorders.