Study Design. Prospective cohort study of 52 patients who had undergone artificial lumbar disc replacement.
Objectives. To evaluate the implantation accuracy of prosthesis positioning, subsequent facet joint changes and prosthesis migration, and the clinical consequences of implant position.
Summary of Background Data. Accuracy of spinal prosthesis implantation has not been evaluated rigorously, especially with a mini-incision approach. It is unknown if the inexact placement of a mobile device in the spine has any biomechanical, radiographic, or clinical repercussions.
Methods. A total of 52 consecutive patients were treated using standard methods of disc implantation with an intervertebral prosthesis. Computed tomography scans were performed within 3 days and again at 6 to 24 months. An independent radiologist analyzed the images for prosthesis position, rotation, migration, and facet changes. Results were compared with clinical outcome, measured by the Visual Analog Scale and Oswestry Disability Index.
Results. Deviation of the prosthesis from the center position was under 1.2 mm, and rotation off of midline was under 12°. Follow-up CT scans showed no migration or facet changes. Regression analysis showed no correlation of prosthesis position with clinical outcome.
Conclusions. Current prosthetic disc implantation methods, with minimally invasive access techniques, are relatively accurate. Although there can be deviation of the prosthesis from ideal placement, no repercussions were attributable.