Abstract
ObjectiveTo compare changes in foraminal motion at two time points post-surgery between artificial disc replacement (ADR) and anterior cervical discectomy and fusion (ACDF).MethodsEight 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.ResultsIn 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).ConclusionsChanges 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. These changes are contrary to the notion that motion at adjacent levels continue to increase following ACDF as compared to ADR over the long term.
Highlights
Anterior cervical spine surgery is commonly performed for the treatment of cervical spinal disease or deformity, accounting for more than 80% of the 1.3 million procedures performed on the cervical spine in the period between 2002 and 2009 [1]
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 Anterior Cervical Disc Replacement (ADR) for neck extension
It has been proposed that ACDF, and to a lesser extent ADR, may accelerate degeneration at adjacent levels leading to the development of adjacent segment disease (ASD) in the long term [2,3,4,5]
Summary
Anterior cervical spine surgery is commonly performed for the treatment of cervical spinal disease or deformity, accounting for more than 80% of the 1.3 million procedures performed on the cervical spine in the period between 2002 and 2009 [1]. It has been proposed that ACDF, and to a lesser extent ADR, may accelerate degeneration at adjacent levels leading to the development of adjacent segment disease (ASD) in the long term [2,3,4,5]. Despite favorable clinical outcomes for ADR over ACDF, the evidence connecting this result to the motion-limiting (for ACDF) or motion-preserving (for ADR) nature of the surgeries is lacking. In lack of such information further developmental efforts for design of new devices or treatment approaches may be misguided
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