Magnetic resonance imaging of periarticular titanium screws

Magnetic resonance imaging (MRI) may be the most sensitive modality for detecting post-traumatic degeneration of articular cartilage. Magnetic resonance imaging must accurately depict articular cartilage in the presence of periarticular fracture stabilization devices to be effective for postoperative imaging of articular fractures. This study examines how close titanium screws can be inserted to tibial articular surfaces and still allow accurate MRI of the overlying articular cartilage. Cannulated titanium screws were inserted at varying distances from subchondral bone in the proximal and distal tibiae of embalmed human cadaveric legs, which were then imaged using a standard nonfat-saturated fast low angle shot two-dimensional sequence (FLASH 2D). The distance from the center of the screw to the subchondral bone and the thickness of the articular cartilage directly overlying the screw was then determined by direct measurement and by measurement on the scanned images. To allow FLASH 2D MRI of the articular cartilage, 7.3-mm screws had to be at least 13 mm from the subchondral bone, and 4.5-mm screws had to be at least 12 mm from the subchondral bone. For MRI to be effective for the postoperative imaging of the articular surface following severe articular fractures of the tibia, titanium fracture hardware must be farther away from the articular surface than these minimum distances. Alternate materials for stabilizing articular fractures are available and may allow clearer and more accurate imaging of the articular cartilage when inserted close to the articular surface.