The Spine Journal
Volume 9, Issue 7, July 2009, Pages 551-555

Effect of intervertebral disc height on postoperative motion and clinical outcomes after Prodisc-C cervical disc replacement

Chan W.B. Peng MD, a, , Martin Quirnoa MDa, John A. Bendo MDa, Jeffrey M. Spivak MDa and Jeffrey A. Goldstein MDa

aDepartment of Orthopaedic Surgery, NYU Hospital for Joint Diseases, 301 East 17th Street, New York, NY 10003, USA

Received 6 October 2008; accepted 20 March 2009. Available online 17 May 2009.


Background context

Cervical total disc replacement (TDR) is an emerging technology. However, the factors that influence postoperative range of motion (ROM) and patient satisfaction are not fully understood.

Purpose

To evaluate the influence of pre- and postoperative disc height on postoperative motion and clinical outcomes.

Study design/setting

Retrospective review of patients enrolled in prospective randomized Food and Drug Administration (FDA) trial.

Patient sample

One hundred sixty-six patients with single-level ProDisc-C arthroplasty performed were evaluated.

Outcome measures

ROM and clinical outcomes based on Neck Disability Index (NDI) and Visual Analog Scale (VAS) were assessed.

Methods

Preoperative and postoperative disc height and ROM were measured from lateral and flexion-extension radiographs. Student t test and Spearman's rho tests were performed to determine any correlation or “threshold” effect between the disc height and ROM or clinical outcome.

Results

Patients with less than 4 mm of preoperative disc height had a mean 1.8° increase in flexion-extension ROM after TDR, whereas patients with greater than 4 mm of preoperative disc height had no change (mean, 0°) in flexion-extension ROM (p=.04). Patients with greater than 5 mm of postoperative disc height have significantly higher postoperative flexion-extension ROM (mean, 10.1°) than those with less than 5 mm disc height (mean, 8.3°, p=.014). However, patients with greater than 7 mm of postoperative disc height have significantly lower postoperative lateral bending ROM (mean, 4.1°) than those with less than 7 mm disc height (mean, 5.7°, p=.04). It appears that the optimal postoperative disc height is between 5 and 7 mm for increased ROM on flexion extension and lateral bending. There was a mean improvement of 30.5 points for NDI, 4.3 points for VAS neck pain score, and 3.9 points for VAS arm pain score (all p<.001). No correlation could be found between clinical outcomes and disc height. Similarly, no threshold effect could be found between any specific disc height and NDI or VAS.

Conclusion

Patients with greater disc collapse of less than 4 mm preoperative disc height benefit more in ROM after TDR. The optimal postoperative disc height range to maximize ROM is between 5 and 7 mm. This optimal range did not translate into better clinical outcome at 2-year follow-up.

Copyright © 2009 Elsevier Inc. All rights reserved.