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Biomechanical Motion Changes in Adjacent and Noncontiguous Segments Following Single-Level Anterior Cervical
Darren R Lebl1, Kathleen N Meyers2, Franziska C S Altorfer3
1Department of Spine Surgery, Hospital for Special Surgery, New York, NY, USA research@leblspinemd.com.
International Journal of Spine Surgery
|June 12, 2024
Summary
Anterior cervical discectomy and fusion (ACDF) alters cervical spine motion beyond adjacent levels. Compensatory hypermobility can occur at noncontiguous segments, influencing surgical planning.
Area of Science:
- Biomechanical analysis of spinal fusion procedures.
- Cervical spine kinematics and motion segment analysis.
Background:
- Anterior cervical discectomy and fusion (ACDF) can cause adverse biomechanical effects on adjacent spinal segments.
- The impact of ACDF on nonadjacent cervical levels remains poorly understood.
Purpose of the Study:
- To investigate the biomechanical effects of ACDF on cervical spine kinematics beyond the immediate fusion site.
- To test the hypothesis that compensatory motion after single-level ACDF is distributed to noncontiguous spinal levels.
Main Methods:
- Six human cervical spines (C2-T1) were analyzed using CT scans and 3D motion capture.
- Range of motion (ROM) was measured at each level before and after single-level ACDF at C5-C6.
- An inverse kinematics model correlated CT reconstructions with motion capture data.
Main Results:
- Single-level ACDF at C5-C6 significantly reduced motion (-6.8°, P = 0.002).
- No significant ROM changes were observed in immediately adjacent segments (C4-C5, C6-C7).
- Hypermobility occurred in noncontiguous segments in 66% of specimens, and in adjacent segments in 42%.
Conclusions:
- Single-level ACDF affects cervical spine ROM at noncontiguous levels, not just adjacent ones.
- Compensatory motion patterns may be influenced by pre-existing degeneration in noncontiguous segments.
- Hypermobility may not consistently manifest in segments directly adjacent to the ACDF site.
