THE RADIOGRAPHIC AND IMAGING CHARACTERISTICS OF POROUS TANTALUM IMPLANTS WITHIN THE HUMAN CERVICAL-SPINE

Study Design. Seven cadaveric cervical spines were implanted with a po rous tantalum spacer and a titanium alloy spacer, and their radiograph ic and imaging characteristics were evaluated. Objective. To determine the radiographic characteristics of porous tantalum and titanium impl ants used as spacers in the cervical spine. Summary of Background Data . Anterior decompressive surgery of the disc space or the vertebral bo dy creates a defect that frequently is repaired with autologous bone g rafts to promote spinal fusion. Donor site morbidity, insufficient don or material, and additional surgical time have spurred the development of biomaterials to replace or supplement existing spinal reconstructi on techniques. Although the promotion of a solid bony fusion is critic al, the implanted biomaterial should be compatible with modern imaging techniques, should allow visualization of the spinal canal and neural foramina, and should permit radiographic assessment of bony ingrowth. Methods. Cadaveric spines containing the implants were imaged with pl ain radiography, computerized tomography, and magnetic resonance imagi ng. The image distortion produced by the implants was determined quali tatively and quantitatively. Results. The tantalum and titanium spacer s were opaque on plain radiographic films. On computed tomographic sca ns, more streak artifact was associated with the tantalum implants tha n with the titanium. On magnetic resonance imaging, the porous tantalu m implant demonstrated less artifact than did the titanium spacer on T 1- and T2-weighted spin echo and on T2-weighted gradient-echo magneti c resonance images. Overall; the tantalum im pla nt produced less arti fact on magnetic resonance imaging than did the titanium spacer and th erefore allowed for better visualization of the surrounding bony and n eural structures. Conclusion. The material properties of titanium and porous tantalum cervical interbody implants contribute to their differ ential appearance in different imaging methods. The titanium implant a ppears to image best with computed tomography, whereas the porous tant alum implant produces less artifact than does the titanium implant on several magnetic resonance imaging sequences.