Association between uptake in 18F-fluoride PET and mechanical load stress in the hip joint

Background 18F-fluoride Positron Emission Tomography (fluoride-PET) is a functional imaging technique that mainly detects the acceleration of bone metabolism. We previously demonstrated the usefulness of fluoride-PET in various stages of hip osteoarthritis. Interestingly, the uptake was recognized even in the case without marked radipgraphical findings. The significant uptake in fluoride-PET in the hip joint, which is caused by the acceleration of bone metabolism in the subchondral bone, may be related with the mechanical load stress concentration due to some morphologic factor. However, there have been no previous studies that examined the relation between uptake in fluoride-PET and mechanical stress. The purpose of this study was to calculate stress distribution from computed tomography(CT) data of hips with coxalgia or dysplastic change by using the finite element analysis(FEA) method, and to examine its association with the uptake in fluoride-PET. Method A total of 30 hips (15 cases) with radiographic dysplastic change or osteoarthritis or no abnormality were enrolled in this study. Each case was investigated by fluoride-PET and CT. The stress distribution in each hip joint was calculated by FEA, and the maximum standardized uptake value (SUVmax) in fluoride-PET was measured as an index of accumulation. The existence of hip pain was reviewed for each joint. We also investigated the influence of hip pain in results of fluoride PET and FEA. FEA Three-dimensional models of the hip were made from the CT data. After adding the information about loading conditions, finite element analysis was performed using Mechanical finder V6.0 (Research Center of Computational Mechanics, Inc.).