Spine. Volume 36(13), 01 June 2011, p 991–996

Sagittal Alignment After Bryan Cervical Arthroplasty

Sasso, Rick C. MD*; Metcalf, Newton H. BS†; Hipp, John A. PhD‡; Wharton, Nicholas D. MS‡; Anderson, Paul A. MD§. Author Information: * Indiana Spine Group, Indiana University School of Medicine, Indianapolis, IN; † Medtronic Inc, Memphis, TN; ‡ Medical Metrics, Inc., Houston, TX; § Department of Orthopedic Surgery and Rehabilitation, University of Wisconsin, WI. © 2011 Lippincott Williams & Wilkins, Inc.

Study Design. Prospective, randomized, Food and Drug Administration Investigational Device Exemption trial from one study site.

Objective. Examine the radiographic sagittal alignment of the Bryan cervical disc for one-level disease.

Summary of Background Data. Prospective, randomized studies demonstrate Bryan arthroplasty provides statistically better functional outcomes than anterior cervical discectomy and fusion. Uncontrolled case reports describe kyphosis after disc replacement. No prospective study has critically assessed sagittal alignment after cervical arthroplasty.

Methods. Forty-eight patients reviewed with a minimum follow-up of 2 years. Quantitative motion analysis determined the change in overall (C2–C7) and treatment-level sagittal alignment, disc space heights, and range of motion.

Results. Preoperatively, overall sagittal alignment was equivalent in the two groups. At 24-month follow-up, overall lordosis for the cohorts was not statistically different from preoperative values for each group. In addition, overall lordosis was not significantly different at 24 months when comparing Bryan patients with the fusion patients. The average change in disc angle from preoperative to immediate postoperative at the treated level in the Bryan disc group was a nonsignificant increase in lordosis of 0.92°. The anterior disc height was the same at all time points, but the posterior disc height was slightly (0.7 mm) more in the Bryan than in the fusion patients (P = 0.04). The angular range of motion in the Bryan group was statistically equivalent at all time points. At the fused levels, average range of motion decreased from 6.4° to 0.9° at 24 months (P < 0.0001).

Conclusion. With the Bryan disc, there was an insignificant increase in lordosis of 0.9° at immediate postoperative time point. Overall cervical sagittal alignment is not different between the experimental and control populations. This prospective study does not demonstrate a clinically significant increase in segmental kyphosis after Bryan disc arthroplasty. Global cervical lordosis is statistically equivalent between arthroplasty and fusion groups at 2 years follow-up.