Disc Changes in the Bridged and Adjacent Segments After... : Spine (original) (raw)

Diagnostics

Disc Changes in the Bridged and Adjacent Segments After Dynesys Dynamic Stabilization System After Two Years

Kumar, Abhishek MRCS; Beastall, James MRCS; Hughes, Justin MRCS; Karadimas, Efthimios J. MD, PhD; Nicol, Malcolm MRCS; Smith, Francis FRCR; Wardlaw, Douglas FRCS(Orth)

From the Department of Orthopaedic Surgery, Woodend Hospital, Aberdeen, Scotland, UK.

Acknowledgment date: February 28, 2008. Revision date: June 11, 2008. Acceptance date: August 5, 2008.

The device(s)/drug(s) that is/are the subject of this manuscript is/are being evaluated as a part of an ongoing FDA-approved investigational protocol (IDE) or corresponding national protocol. In the US, the Dynesys Spinal System is cleared for use as an adjunct to fusion, it is neither cleared nr approved for non fusion applications and is currently under study as an investigational device.

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

Research Assistance was provided by Zimmer GmbH (Winterthur, CH) who provided funding and advice for research staff.

Address correspondence and reprint requests to Abhishek Kumar, MRCS, Department of Orthopaedic Surgery, Woodend Hospital, Eday Road, Aberdeen, AB15 6XS; E-mail: [email protected]

Study Design.

Prospective case series.

Objective.

To study the radiologic changes in the intervertebral disc after Dynesys dynamic stabilization.

Summary of Background Data.

Adjacent segment disc degeneration is one of the potential complications of fusion surgery. It has been proposed that nonfusion motion preservation surgery may prevent accelerated adjacent segment degeneration because of the protective effect of persisting segmental motion.

Methods.

Thirty-two patients who underwent Dynesys procedure between November 2002 and June 2004 and have completed 2-year follow-up MRI scans were included in this study. Preoperative and 2 year postoperative lumbar MRI scans were evaluated by 2 independent observers. T2-weighted mid-sagittal images were used and disc degeneration classified according to the Woodend classification of disc degeneration. Anterior and posterior intervertebral disc heights were also measured.

Results.

Of the 32 patients, 20 patients underwent Dynesys procedure alone and 12 underwent additional fusion at 1 or more levels. A total of 70 levels were operated on, of which 13 levels were fused.

There was a statistically significant increase in the mean Woodend score at the operated levels in the Dynesys alone group, a change from 1.95 before surgery to 2.52 after surgery (P < 0.001). The mean Woodend scores changed from 1.27 preoperative to 1.55 postoperative (P = 0.066) at the proximal adjacent levels, and from 1.37 to 1.62 at the distal levels (P = 0.157). There was good interobserver agreement (weighted κ score of 0.819). The anterior intervertebral disc height reduced by 2 mm from 9.25 to 7.17 (P < 0.001). The posterior disc height increased by 0.14 mm but this change was not significant.

Conclusion.

Disc degeneration at the bridged and adjacent segment seems to continue despite Dynesys dynamic stabilization. This continuing degeneration could be due to natural disease progression.