The nuchal ligament restrains cervical spine flexion

Study Design. A biomechanical study using a cadaver model was conducted to define the function of the nuchal ligament in the restraint of flexion of the cervical spine. Objective. To test the hypothesis that surgical resection of the nuchal ligament significantly reduces the structural restraints to cervical flexion. Summary of Background Data. Although previous studies have examined the role of the posterior ligaments and capsules on cervical stability, no prior study has quantified the biomechanical significance of the nuchal ligament. The clinical significance may include progressive loss of lordosis or even kyphosis after trauma or posterior surgical procedures such as laminectomy, laminoplasty, or tumor resection. Methods. Cervical spines from the occiput to the first thoracic vertebra were harvested from 12 human cadavers. Specimens were tested under 3 conditions: all ligaments intact, after resection of the nuchal ligament, and then after additional resection of the supraspinous, interspinous, and yellow ligaments. Flexion moments were applied; load and displacement were measured. Changes in flexion range of motion and tangent stiffness between treatment conditions were statistically compared. Results. The flexion range increased 28% after removing the nuchal ligament. After subsequent resections, the flexion range increased 52% compared with intact ( P <0.005). Tangent stiffness decreased 27% after nuchal ligament resection; after all resections, stiffness was 35% lower than intact (P < 0.05). Conclusion. Resection of the nuchal ligament increased the flexion range of motion and decreased stiffness in flexion. Injury to the nuchal ligament may increase the risk of cervical spine instability and malalignment.