Dynamic foraminal dimensions during neck motion 6.5 years after fusion and artificial disc replacement

Abstract

Objective To compare changes in foraminal motion at two time points post-surgery between artificial disc replacement (ADR) and anterior cervical discectomy and fusion (ACDF). Methods Eight ACDF and 6 ADR patients (all single-level C5-6) were tested at 2 years (T1) and 6.5 years (T2) post-surgery. The minimum foraminal height (FH.Min) and width (FW.Min) achieved during neck axial rotation and extension, and the range of these dimensions during motion (FH.Rn and FW.Rn, respectively) were measured using a biplane dynamic x-ray system, CT imaging and model-based tracking while patients performed neck axial rotation and extension tasks. Two-way mixed ANOVA was employed for analysis. Results In neck extension, significant interactions were found between year post-surgery and type of surgery for FW.Rn at C5-6 (p<0.006) and C6-7 (p<0.005), and for FH.Rn at C6-7 (p<0.01). Post-hoc analysis indicated decreases over time in FW.Rn for ACDF (p<0.01) and increases in FH.Rn for ADR (p<0.03) at the C6-7 adjacent level. At index level, FW.Rn was comparable between ACDF and ADR at T1, but was smaller for ACDF than for ADR at T2 (p<0.002). In axial rotation, differences were found between T1 and T2 but did not depend on type of surgery (p>0.7). Conclusions Changes were observed in the range of foraminal geometry at adjacent levels from 2 years to 6.5 years post-surgery that were different between ACDF and ADR for neck extension.

In vivo cervical vertebrae kinematic studies based on dual fluoroscopic imaging system measurement: A narrative review

“…This suggests that the retained motion after disc replacement may not fully replicate the in vivo motion of the original disc. At 6.5 years postoperatively, Azad et al found a decrease in the variability of the foraminal area of the adjacent segment after ACDF surgery and a slight increase after ADR surgery [ 33 ]. Meanwhile Yeni et al found minimal differences in the ROM between the two surgical procedures [ 41 ].…”

“…Intervertebral disc height showed no differences in surgical approach, time points, or interactions. The authors pointed out that cervical extension is a more sensitive test for detecting surgery-related changes in intervertebral foramen motion [ 33 , 34 ]. The latest research suggests that the cervical motion pattern in the cervical fusion group is more rigid, while the cervical motion pattern in the ADR group is closer to the physiological pattern of normal cervical motion [ 41 ].…”

“… Yeni et al, 2018 [ 32 ] Post C5–C6 ACDF surgery subjects, 16 (4 M, 12F), 28-71 C3–C7 intervertebral foramen Extension, Axial rotation ROM Compared to patients undergoing ADR, those undergoing ACDF experience a greater reduction in foraminal area at the operated segment. Post C5–C6 ADR surgery subjects, 7 (3 M, 4F), 38-57 Azad et al, 2020 [ 33 ] Post C5–C6 ACDF surgery subjects, 8 (4 M, 4F), 42.5 ± 10.1 C4–C7 intervertebral foramen Extension, Axial rotation ROM Long-term kinematic studies post-surgery reveal a decrease in variability in foraminal area of adjacent segments after ACDF, while there is a slight increase after ADR. Post C5–C6 ADR surgery subjects, 6 (2 M, 4F), 48.2 ± 7.5 Guo et al, 2021 [ 34 ] Healthy subjects, 10 (4 M, 6F), 30-59 C3–C7 vertebral bodies Flexion-Extension, Axial rotation ROM Preservation of motion therapy should further consider the preoperative spinal disease status to restore physiological segmental ROM.…”