Three-dimensional kinematic analysis of the cervical spine after anterior cervical decompression and fusion at an adjacent level: a preliminary report

Abstract

Purpose Development of adjacent segment degeneration following anterior cervical decompression and fusion (ACDF) is still controversial, as adjacent-level kinematics is poorly understood. This study reports preliminary data from a high-accuracy 3D analysis technique developed for in vivo cervical kinematics. Methods From nine cervical spondylosis patients, four underwent single-level ACDF, and five underwent two-level ACDF using cylindrical titanium cage implant(s). Pre-and post-surgical CT scans were taken in flexion, neutral and extended positions, allowing us to compute segmental ranges of motion for rotation and translation, and 3D disc-height distributions. Differences in segmental motions and disc-height between fused and adjacent levels were analyzed with a Wilcoxon signed-rank test. Results are presented as mean ± SEM. Results The flexion/extension angular-ROM at the fusion level decreased after surgery (7.46 ± 1.17°vs. 3.14 ± 0.56°, p \ 0.003). The flexion/extension angular-ROM at one caudal adjacent level to the fusion level (3.97 ± 1.29°) tended to be greater post-operatively (6.11 ± 1.44°, p = 0.074). Translation in the anterior-posterior direction during flexion/ extension at the fusion level decreased after surgery (1.22 ± 0.20 mm vs. 0.32 ± 0.11 mm, p \ 0.01). No differences were found in adjacent-level disc heights between both study time-points. Conclusions This study showed increased segmental motion in flexion/extension angular-ROM at one level adjacent to ACDF. However, increases in the rotational angular-ROM were not statistically significant when cranial/caudal adjacent levels were analyzed separately. This preliminary study highlighted the capabilities of a 3D-kinematic analysis method to detect subtle changes in kinematics and disc height at the adjacent levels to ACDF. Thus, reliable evidence related to ACDF's influence on adjacent-level cervical kinematics can be collected.

Anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA) for two contiguous levels cervical disc degenerative disease: a meta-analysis of randomized controlled trials

“…Phillips et al [24] suggest that cervical disc arthroplasty at two levels can provide near-normal mobility at both levels without destabilizing the implanted segments or affecting adjacent segment motions. There is strong clinical evidence to show that degeneration occurs at spinal segments adjacent to fused levels in the cervical spine [25], however, A meta-analysis of prospective studies, there is no difference in the rate of ASD for ACDF versus CDA in cervical single-level disc degeneration [26] with but its exact cause, whether related to the biomechanical effect of fusion or natural history, is currently controversial. The meta-analysis suggested that there was significant difference between both groups (P \ 0.00001, RR = 0.48, 95 % CI = 0.40-0.58).…”

“…There were two primary reasons for this substantial significance. First, many biomechanical and kinematic researches showed that maintaining the range of motion at the operative level can decrease the incidence of adjacent level degeneration [9,25,40,41]. Laxer et al [42] reported that the adjacent segment discs experience substantially lower pressure in CDA compared with simulated anterior cervical fusion at two levels.…”

The effect of multilevel anterior cervical fusion on neck motion

“…This may play a major role in cervical ROM following multilevel anterior cervical fusion. Although compensatory motion always developed at the adjacent level [8,[18][19][20], the compensation may not be enough for the loss of motion of 3 or 4 segments.…”

Evaluation of mobility and stability in the Discover artificial disc: an in vivo motion study using high-accuracy 3D CT data

“…30,31 Previous studies on spinal mobility have been performed with varying accuracy, depending on the technique used. 9,12,14,[19][20][21][22][23]28,37,40 Radiostereometric analysis (RSA) has been shown to be the most accurate; 1,26,27 however, the technique always requires implantation of tantalum markers and is therefore an invasive method. The accuracy is also dependent on how the markers are distributed within the vertebrae.…”