Usefulness of Magnetic Resonance Imaging in the Evaluation of Spine Following Instrumentation with Titanium Implants

ABSTRACT

Over the past six years, titanium alloy has been replacing the stainless steel in spinal implants owing to its magnetic resonance imaging(MRI) compatibility. However, studies about the usefulness of MRI, from a clinical standpoint, when it is used for spinal implants have been scarce. The purpose, therefore, is to determine whether postoperative MRIs would provide satisfactory information in evaluating the spine having various titanium implants. Authors reviewed the spinal MR images of sixteen patients who had previously received eleven different kinds of titanium implants, and compared postoperative images to preoperative images regarding the quality of images of spinal cord, nerve root, spinal canal, and the aforementioned implants. Types of implants included anterior cervical plate/screws, lateral cervical mass plate/screws, Halifax interlaminar clamps, anterior thoracolumbar rods/screws, posterior thoracolumbar rods/hooks, and posterior thoracolumbar transpedicular rods/screws. Anterior cervical plate/screws, lateral cervical mass plate/screws, Halifax clamps, and anterior thoracolumbar rod/screws produced small distortions of the images at the spinal canal or neural foramen. In contrast, posterior thoracolumbar transpedicular rods/screws created severe image distortions at the neural foramen in the postoperative MRIs. Metal-induced artifacts were most marked in the image from gradient echo sequence. Posterior thoracolumbar rods/hooks produced some artifacts at the posterior portion of the spinal canal. Although our series are limited in number, it can be concluded that MRI is informative and it is useful in postoperative evaluation of the spine with most types of titanium implants. However, postmyelogram computed tomography is recommended in cases where posterior thoracolumbar transpedicular rods/screws have been used.