#261 Cervical Posterior Foraminotomy’s Effect on Segmental Range of Motion in the Setting of Total Disc Arthroplasty

General Session: Cervical - Clinical Outcomes

Presented by: J. Cody

Author(s):

R.W. Tracey (1)
A.J. Bevevino (1)
R.A. Lehman (1)
D.G. Kang (1)
D. Ambati (1)
R. Gaume (1)
D.E. Gwinn (1)
A.E. Dmitriev (1)
J. Cody (1)

(1) Walter Reed National Military Medical Center, Orthopaedic Surgery, Bethesda, MD, USA

Abstract

Introduction: Total disc replacement (TDR) is gaining popularity for the treatment of cervical radiculopathy. In spite of a proven track record, recurrent same level radiculopathy and adjacent level disease remain prevalent with significant clinical problems. Posterior foraminotomy offers the ability to decompress cervical nerves roots while avoiding the need to extend a previous fusion or revise implants. However, the safety of foraminotomy in the setting of TDR is unknown. With this in mind, the goal of this study was to investigate the effect on cervical segmental stability that posterior foraminotomy has following TDR.

Methods:Segmental non-destructive range of motion (ROM) (axial rotation, flexion/extension, and lateral bending) was analyzed in nine human cadaveric cervical spine specimens. The intact state was first tested to determine baseline C4 to C7 ROM. Following this, each specimen was sequentially tested according to the following four experimental groups: Group 1=C56 TDR, Group 2=C56 TDR with unilateral C56 foraminotomy, Group 3=C56 TDR with bilateral C56 foraminotomy, and Group 4=C56 TDR with C56 and C45 bilateral foraminotomy. After testing, one-way ANOVA with a post hoc Tukey test was used to detect statistically significant differences in ROM between the experimental groups.

Results: No differences in ROM was found between the intact, TDR, and foraminotomy specimens at C45 or C67 (p>0.1). There was a step wise increase in C56 axial rotation from the intact state (8°) to Group 4 (12°), although the difference did not reach statistical significance (p>0.2). At C56, the degree of lateral bending remained relatively constant, 8° in the intact state to 8.8° in Group 4, and was not statistically different in any of the tested groups (p=0.8). Flexion and extension at C56 was significantly higher in the foraminotomy specimens, Groups 2 (18.1°), 3 (18.6°), and 4 (18.2°), compared to the intact state, 11.2° (p< 0.05). However, no ROM difference was found within foraminotomy Groups (2-4;p>0.8) or between the foraminotomy groups and the TDR group (Group 1), 15.3° (p>0.4).

Discussion: Posterior foraminotomy increases cervical flexion and extension when performed at the same level as a TDR. On the other hand, axial rotation and lateral bending are not increased by TDR or the addition of one or more foraminotomies. The observed increase in ROM results from the initial unilateral same level foraminotomy and is not further affected by the addition of another same level foraminotomy or bilateral adjacent level foraminotomies. In contrast to the significant difference between the intact specimens and those with a TDR plus foraminotomy, the ROM difference between the TDR specimens and those with foraminotomies was small, approximately 3 degrees, and not significant. Therefore, from a biomechanical standpoint, it appears safe to perform one or several posterior foraminotomies in the setting of a previously placed cervical disc replacement.