Study Design. Post hoc analysis of data acquired in a prospective, randomized, controlled trial.
Objective. To compare adjacent segment motion after anterior cervical discectomy and fusion (ACDF) versus cervical total disc arthroplasty (TDA).
Summary of Background Data. TDA has been designed to be a motion-preserving device, thus theoretically normalizing adjacent segment kinematics. Clinical studies with short-term follow-up have yet to demonstrate a consistent significant difference in the incidence of adjacent segment disease.
Methods. Two hundred nine patients at 13 sites were treated in a prospective, randomized, controlled trial of ACDF versus TDA for single-level symptomatic cervical degenerative disc disease (SCDD). Flexion and extension radiographs were obtained at all follow-up visits. Changes in ROM were compared using the Wilcoxon signed-rank test and the Mann-Whitney U test. Predictors of postoperative ROM were determined by multivariate analysis using mixed effects linear regression.
Results. Data for 199 patients were available with 24-month follow-up. The groups were similar with respect to baseline demographics. A significant increase in motion at the cranial and caudal adjacent segments after surgery was observed in the ACDF group only (cranial: ACDF: +1.4° (0.4, 2.4), P = 0.01; TDA: +0.8°, (−0.1, +1.7), P = 0.166; caudal: ACDF: +2.6° (1.3, 3.9), P < 0.0001; TDA: +1.3, (−0.2, +2.8), P = 0.359). No significant difference in adjacent segment ROM was observed between ACDF and TDA. Only time was a significant predictor of postoperative ROM at both the cranial and caudal adjacent segments.
Conclusion. Adjacent segment kinematics may be altered after ACDF and TDA. Multivariate analysis showed time to be a significant predictor of changes in adjacent segment ROM. No association between the treatment chosen (ACDF vs. TDA) and ROM was observed. Furthermore clinical follow-up is needed to determine whether possible differences in adjacent segment motion affect the prevalence of adjacent segment disease in the two groups.
Multivariate analysis of adjacent segment motion data from an investigational device exemption trial was performed. Time from surgery is a significant predictor of changes in adjacent segment motion. No difference in adjacent segment change was noted between cervical disc arthroplasty and fusion.
* Department of Orthopedic Surgery, Washington University, St. Louis, MO.
† Department of Orthopaedic Surgery Service, Madigan Army Medical Center, Tacoma, WA.
‡ Department of Orthopaedic Surgery, Ochsner Medical Center, New Orleans, LA.
Address correspondence and reprint requests to Michael P. Kelly, MD, Department of Orthopedic Surgery, Washington University, 660 S. Euclid Avenue, Box 8233, St. Louis, MO 63110; E-mail: firstname.lastname@example.org
Supported by Synthes USA Products, LLC, West Chester, IRB: 10-00626
Acknowledgement date: October 9, 2009. 1st Revision: April 9, 2010. 2nd Revision: June 4, 2010. Acceptance: June 7, 2010.
The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.
Corporate/Industry funds were received in support of this work.
One or more of the author(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: e.g., honoraria, gifts, consultancies, royalties, stocks, stock options, decision making position.