Study Design. Human cadaveric biomechanical analysis.
Objective. To investigate the effect on cervical spine segmental stability that results from a posterior foraminotomy after cervical disc arthroplasty (CDA).
Summary of Background Data. Posterior foraminotomy offers the ability to decompress cervical nerves roots while avoiding the need to extend a previous fusion or revise an arthroplasty to a fusion. However, the safety of a foraminotomy in the setting of CDA is unknown.
Methods. Segmental nondestructive range of motion (ROM) was analyzed in 9 human cadaveric cervical spine specimens. After intact testing, each specimen was sequentially tested according to the following 4 experimental groups: group 1 = C5–C6 CDA, group 2 = C5–C6 CDA with unilateral C5–C6 foraminotomy, group 3 = C5–C6 CDA with bilateral C5–C6 foraminotomy, and group 4 = C5–C6 CDA with C5–C6 and C4–C5 bilateral foraminotomy.
Results. No differences in ROM were found between the intact, CDA, and foraminotomy specimens at C4–C5 or C6–C7. There was a step-wise increase in C5–C6 axial rotation from the intact state (8°) to group 4 (12°), although the difference did not reach statistical significance. At C5–C6, the degree of lateral bending remained relatively constant. Flexion and extension at C5–C6 was significantly higher in the foraminotomy specimens, groups 2 (18.1°), 3 (18.6°), and 4 (18.2°), compared with the intact state, 11.2°. However, no ROM difference was found within foraminotomy groups (2–4) or between the foraminotomy groups and the CDA group (group 1), 15.3°.
Conclusion. Our results indicate that cervical stability is not significantly decreased by the presence, number, or level of posterior foraminotomies in the setting of CDA. The addition of foraminotomies to specimens with a pre-existing CDA resulted in small and insignificant increases in segmental ROM. Therefore, biomechanically, posterior foraminotomy/foraminotomies may be considered a safe and viable option in the setting of recurrent or adjacent level radiculopathy after cervical disc replacement.
Level of Evidence: N/A
The study was conducted as a biomechanical analysis investigating the effects on segmental cervical spine motion of posterior foraminotomy in combination with cervical disc arthroplasty. The results indicate that a posterior foraminotomy can be added to a specimen with a pre-existing disc arthroplasty, without significantly increasing range of motion.
From the Walter Reed National Military Medical Center, Bethesda, MD. Dr. Lehman is now at the Washington University in St. Louis, St. Louis, MO.
Address correspondence and reprint requests to Adam J. Bevevino, MD, Walter Reed National Military Medical Center, Department of Orthopaedic Surgery and Rehabilitation, 8901 Wisconsin Ave, Bethesda, MD 20889; E-mail: firstname.lastname@example.org
Acknowledgment date: January 31, 2014. First revision date: April 28, 2014. Second revision date: May 22, 2014. Acceptance date: May 28, 2014.
The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication.
No funds were received in support of this work.
No relevant financial activities outside the submitted work.