The cysts in patients with silicone synovitis are filled with hypertrophic synovium, not fluid like typical degenerative cysts. The signal intensity observed on MR images will reflect this pathology and the cysts will be of intermediate signal on T1 and T2-weighted images. In the first study to report MR imaging findings, the authors reported intermediate intensity to mild hyperintensity on proton-density and T2-weighted images in all patients.5 (Figures 6a,7a,8a) They also observed deformity or fracture of the prosthesis in all patients. In addition, all patients showed hypointense foci on all sequences felt to represent silicone fragments or fibrotic reaction. (Figures 8a and 9a)
(9a) A sagittal T1-weighted image from the same patient as images 1a and 1b, obtained at the lateral margin of the joint. The distal fibula and peroneal tendons are seen, as is the fifth metatarsal base. A region of synovitis anterior to the distal fibula has peripheral foci of low signal intensity (arrows) which may represent fragments of the subtalar prosthesis.
Imaging of prosthetic joints ..
(8a) Same patient as Figure 7. Sagittal fat-suppressed proton-density weighted image. Extensive cyst formation in the capitate and lunate bones (asterisks) is of intermediate signal intensity. The subchondral cysts within the distal radius (arrowheads) are of high signal and may reflect degenerative cysts due to secondary osteoarthrosis. Small foci of low signal at the dorsal and volar aspects of the wrist (small arrows) may reflect debris or fragments from the prosthesis.