The authors studied the usefulness of magnetic resonance imaging in assessing vascularity of the scaphoid in the presence of a titanium alloy screw. Eleven patients who had undergone Herbert screw fixation of an acute scaphoid fracture or fracture non-union were included in this study. In all cases, MRI artifact from the Herbert screw was minimal and did not preclude an accurate assessment of marrow signal changes in the proximal or distal scaphoid poles.
The Herbert, Herbert Whipple and the Acutrak screws are all made of titanium alloy which is a non-ferromagnetic material. In contrast, the AO cancellous screw and Kirschner wires are made of stainless steel, a ferromagnetic material which produces more MRI artifact than titanium. The MRI scans reported in this study were obtained with a 1.0 Tesla magnet without gadolinium enhancement. A recent report has shown that intravenous gadolinium enhancement with T1-weighted fat suppressed technique will significantly improve the accuracy in assessing osteonecrosis (Cerezal et. al, Am J Roentgen 174:141-149, 2000). Additional techniques for improving the quality of MRI scans include the use of a dedicated wrist surface coil and thin 1mm to 2mm image slices in the plane of the bone.