Comparison of Cervical Spine Stiffness in Individuals With Chronic Nonspecific Neck Pain and an Asymptomatic Comparison Group

This study sought to determine if spinal joint stiffness is different in persons with non-specific neck pain, and whether stiffness magnitude is associated with pain intensity and disability. Manual therapists often evaluate spinal joint stiffness in patients presenting with non-specific neck pain. However, a relationship between stiffness and neck pain has not yet been demonstrated. Spinal stiffness at C7 was objectively measured in participants with chronic non-specific neck pain whose symptomatic spinal level was identified as C7 (n= 12), and age and gender matched asymptomatic controls (n = 12). Stiffness (slope of the linear region of the force-displacement curve) was quantified using a device applying 5 standardized mechanical force cycles to the C7 spinous process while concurrently measuring displacement and resistance to movement. Stiffness was compared between groups using an independent t-test. Spearman’s rho and Pearson’s r were used to determine the extent stiffness magnitude was associated with pain intensity (visual analogue scale) and level of disability (Neck Disability Index) respectively, in the group with neck pain. Participants with non-specific neck pain had greater spinal joint stiffness at C7 compared with asymptomatic individuals (mean difference 1.78 N/mm, 95% CI 0.28, 3.27, P = .022). However, stiffness magnitude in the group with neck pain was not associated (P>.05) with pain intensity or level of disability.

These preliminary results indicate that cervical spine stiffness may be greater in the presence of non-specific neck pain. However, judgements regarding pain intensity and level of disability should not be inferred from examinations of spinal joint stiffness.