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Motion compensation associated with single-level cervical fusion: where does the lost motion go?
John S Schwab1, Denis J Diangelo, Kevin T Foley
1Department of Biomedical Engineering, University of Tennessee Health Science Center, Memphis TN 38103, USA.
Spine
|October 7, 2006
Summary
Single-level cervical spine fusion increases motion in adjacent segments, particularly at lower levels (C5-C6, C6-C7). This compensatory motion highlights the biomechanical impact of fusion on spinal stability.
Area of Science:
- Biomechanics
- Spinal Surgery
- Orthopedics
Background:
- Adjacent segment disease is a clinical concern after spinal fusion.
- Previous research has not specifically investigated the biomechanical effects of single-level cervical fusions at various spinal levels.
Purpose of the Study:
- To compare the biomechanical effects of single-level cervical spine fusions at different spinal levels.
- To analyze changes in segmental motion and global stiffness following fusion.
Main Methods:
- Seven adult human cadaveric cervical spines (C2-T1) were biomechanically tested.
- Spines underwent testing in flexion, extension, lateral bending, and axial rotation under 7 conditions: intact and 6 single-level fused states (C2-C3 to C7-T1).
- Segmental motion and global stiffness were normalized and compared using statistical analysis (ANOVA, SNK test).
Main Results:
- Motion compensation occurred in unfused segments adjacent to the fusion site.
- Significant increases in motion were observed above C3-C4 and C4-C5 fusions, and below C5-C6 and C6-C7 fusions in flexion and extension.
- Lower-level fusions (C5-C6, C6-C7) showed greater compensatory motion at inferior segments compared to superior segments.
Conclusions:
- Single-level cervical fusion leads to increased motion compensation in adjacent spinal segments.
- The location of the fusion impacts the distribution of compensatory motion, with lower-level fusions affecting both superior and inferior segments.
- These findings underscore the biomechanical consequences of cervical fusion and inform surgical decision-making.
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