Insertion of the Artificial Disc Replacement: A Cadaver Study Comparing the Conventional Surgical Technique and the Use of a Navigation System

Comparison of total disc replacement (TDR) with and without computer-assisted surgical navigation. To test and evaluate the accuracy of computer-assisted navigation for the lumbar spine by comparing the traditional C-arm-aided insertion of an arthroplasty device to the navigation-aided insertion of the implant. Previous studies have shown that poor placement of the CHARITE disc can be correlated to worse clinical results. Because of parallax effect, exclusive use of fluoroscopy could make placement of the artificial disc less accurate. False positioning may also lead to spondylolisthesis, disc degeneration of the adjacent segment, subsidence of the disc, and failure of the implant. Ten human cadaver spine specimens were used at 3 lumbar segments (L3-L4, L4-L5, and L5-S1). Before implantation, all artificial discs were planned for "ideal" placement on a digital computed tomography image. Fifteen lumbar intervertebral disc prostheses (Depuy, Raynham, MA) were placed using Vector Vision image guidance (BrainLAB AG, Munich, Germany), by an inexperienced TDR-surgeon. Fifteen lumbar intervertebral disc prostheses were placed with exclusive use of fluoroscopy by an experienced TDR-surgeon. After insertion, DICOM computed tomography scans were analyzed using computer software to assess placement accuracy of each disc prosthesis. The navigated placement of the disc was significantly more accurate. Only 3 navigated disc prostheses were suboptimal and none was poorly placed. Surgical computer-assisted navigation may be a useful tool in the hands of a spine surgeon to achieve more accurate placement of the disc prosthesis. Because of the parallax effect, computer-assisted navigation offers more placement accuracy than stan- dard fluoroscopy. Because the accurate placement of total disc prosthesis has been correlated with better clinical outcome, further study regarding the navigation of the TDR is essential.