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Computed Tomography Assessment of the Accuracy of In Vivo Placement of Artificial Discs in the Lumbar Spine Including Radiographic and Clinical Consequences

Patel, Vikas V., MA, MD*†; Andrews, Carol, MD; Pradhan, Ben B., MS, MD*; Bae, Hyun W., MD*; Kanim, Linda E. A., MA*; Kropf, Michael A., MD*; Delamarter, Rick B., MD*

doi: 10.1097/01.brs.0000209252.21129.8d
Health Services Research

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.

This study reviews postoperative and follow-up CT scans to correlate clinical outcomes with initial positional accuracy. Images were also evaluated for prosthesis migration or subsidence and facet joint changes. No significant clinical correlation was found, and no migration or subsidence was noted.

From the *Spine Institute at St. John’s Hospital, Santa Monica, CA; †Spine Center at the University of Colorado Health Sciences, Denver CO; and ‡Mink Radiologic Imaging, Beverly Hills, CA.

Acknowledgment date: March 9, 2005. First revision date: May 8, 2005. Acceptance date: May 9, 2005.

The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.

Other funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address correspondence and reprint requests to Vikas V. Patel, MA, MD, Chief, Orthopaedic Spine Surgery, University of Colorado Health Sciences, Anschutz Outpatient Pavilion Suite 4200, 1635 Ursula St., Mail Stop F722, PO Box 6510, Aurora CO 80045-0510. E-mail:

© 2006 Lippincott Williams & Wilkins, Inc.