Cervical fusion and Its Impact on Spinal Mobility
My client is a veterinary surgeon, three years post–spinal fusion surgery. She presented to the clinic with complaints of cervical and upper thoracic pain, as well as chronic migraines, with symptoms notably exacerbated after prolonged surgical procedures. The images highlight several assessment findings; however, these represent only a portion of the overall clinical findings identified during evaluation. From a biomechanics standpoint, the spine is a multi-segment system that distributes motion and load across many joints, with each segment contributing a small portion of total movement. When multiple segments are fused, those degrees of freedom are removed. To produce the same overall motion, adjacent segments must move more, at higher relative velocities, and reach end ranges sooner. Over time, this repeated exposure leads to protective tissue adaptations and a gradual reduction in available motion. Fusion also changes how forces are transmitted. The fused region behaves as a stiff structure, causing load to be redirected to the nearest mobile segments. This increases shear, compression, and torsional stress while reducing the system’s ability to dissipate forces efficiently. Functionally, the fusion acts as a rigid lever arm, concentrating stress at the transition zones above and below. This accelerates tissue fatigue, joint irritation, and adaptive stiffness in discs, ligaments, and surrounding musculature. Overall, spinal fusion introduces localized rigidity into an otherwise load-sharing system, increasing mechanical demand and reducing tissue tolerance at adjacent levels over time.
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