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

STUDY DESIGN: Clinical measurement, cross-sectional. OBJECTIVE: To determine if spinal joint stiffness is different in individuals with nonspecific neck pain, and whether stiffness magnitude is associated with pain intensity and disability. BACKGROUND: Manual therapists commonly evaluate spinal joint stiffness in patients presenting with nonspecific neck pain. However, a relationship between stiffness and neck pain has not yet been demonstrated. METHODS: Spinal stiffness at C7 was objectively measured in participants with chronic nonspecific neck pain whose symptomatic spinal level was identified as C7 (n = 12) and in age- and sex-matched asymptomatic controls (n = 12). Stiffness (slope of the linear region of the force-displacement curve) was quantified using a device that applied 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 rho and Pearson r were used to determine the extent to which stiffness magnitude was associated with pain intensity (visual analog scale) and level of disability (Neck Disability Index), respectively, in the group with neck pain. RESULTS: Participants with nonspecific neck pain had greater spinal joint stiffness at C7 compared with asymptomatic individuals (mean difference, 1.78 N/mm; 95% confidence interval: 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. CONCLUSION: These preliminary results suggest that cervical spine stiffness may be greater in the presence of nonspecific neck pain. However, judgments regarding pain intensity and level of disability should not be inferred from examinations of spinal joint stiffness.