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Correlation of Radiostereometric Measured Cervical Range of Motion With Clinical Radiographic Findings After Anterior Cervical Discectomy and Fusion

Park, Soo-An, MD, PhD*; Fayyazi, Amir H., MD; Ordway, Nathaniel R., MS; Sun, Mike H., MD; Fredrickson, Bruce E., MD; Yuan, Hansen A., MD

doi: 10.1097/BRS.0b013e31819819a0
Cervical Spine
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Study Design. Prospective clinical study.

Objective. To evaluate the correlation between clinical radiographic findings and sagittal range of motion (ROM) measured using radiostereometric analysis (RSA) after anterior cervical discectomy and fusion (ACDF).

Summary of Background Data. Evaluation of fusion after ACDF continues to be difficult. Radiographic films including flexion/extension views are routinely used for this purpose. Unfortunately, routine radiographs are insensitive in demonstrating pseudarthrosis. RSA is an accurate technique that can be used in evaluation of segmental motion in vivo and can potentially be used in evaluation of spinal fusion.

Methods. Sixteen patients who underwent multi-level ACDF were enrolled in this study. The procedure was performed in the routine fashion; cervical plates were utilized in each case. Intraoperatively, 3 to 5 tantalum beads were inserted into each vertebral body. At the 1-year follow-up period, sagittal ROM of the operated segments was measured with RSA. In addition, each segment was clinically evaluated for evidence of radiographic fusion by using a 3-point grading system (fused, uncertain, pseudarthrosis) and by measuring the interspinous widening on flexion/extension films. The correlation between the radiographic findings and RSA measured sagittal ROM was evaluated.

Results. Fourteen 2-level and two 3-level procedures representing 31 motion segments were analyzed. The average sagittal ROM of all segments as measured by RSA was 1.3 ± 1.4°. The sagittal ROM of the segments with less than 2 mm of interspinous widening on clinical flexion/extension radiographs was measured at 1.1° ± 1.0° with RSA, whereas the sagittal ROM of the segments with greater than 2 mm of interspinous widening was measured at 3.4° ± 2.9°; a significant correlation was noted between the 2-point grading method and the sagittal ROM (Pearson coefficient, r = 0.504, P = 0.004). Using the 3-point grading system, there were 20 levels graded as fused (0.8° ± 0.9°), 6 levels were graded as uncertain (1.7° ± 1.0°), and 4 levels were graded as pseudarthrosis (3.5° ± 2.7°). The pseudarthrosis group showed significantly greater motion than the fusion group (P = 0.005); a significant correlation was noted between the 3-point grading method and the sagittal ROM (Pearson coefficient, r = 0.561, P = 0.001).

Conclusion. In this study, we evaluated the utility of RSA in evaluating segmental motion after ACDF and demonstrated a significant difference between segments that demonstrated radiographic evidence of fusion when compared with segments that demonstrated evidence of pseudarthrosis. RSA appears to be a quantitative technique capable of assisting in the evaluation of fusion.

Radiostereometric analysis is an accurate technique that can be used in evaluation of segmental motion after anterior cervical discectomy and fusion. The segmental range of motion was significantly different between segments that demonstrated radiographic evidence of fusion in comparison with segments that demonstrated evidence of pseudarthrosis.

From the *Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan, Seoul, South Korea; †VSAS Orthopaedics, Institute for Advanced Healthcare, Allentown, PA; and ‡Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, NY.

Supported by Abbott Spine Inc. (Austin, TX) and by DePuy Spine, Inc. (Raynham, MA).

Acknowledgment date: April 4, 2008. Revision date: October 7, 2008. Acceptance October 13, 2008.

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

Corporate/Industry and institutional funds were received in support of this work. Although one or more of the authors(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization which the author(s) has/have been associated.

The Institutional Review Board at SUNY Upstate Medical University reviewed and approved of the studies conducted that resulted in the data used in this manuscript.

Address correspondence and reprint requests to Nathaniel R. Ordway, MS, Department of Orthopedic Surgery, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210; E-mail: ordwayn@upstate.edu

© 2009 Lippincott Williams & Wilkins, Inc.