Immediate Effect of a Single Cervical Spinal Manipulation on Cervical Movement Pattern

INTRODUCTION Non-specific neck pain is defined as pain in the posterior and lateral aspect of the neck between the superior nuchal line and the spinous process of the first thoracic vertebra with no signs or symptoms of major structural pathology. It is a common musculoskeletal disorder that leads to substantial disability, discomfort, and reduced cervical mobility, resulting in enormous health costs in terms of treatment and work absenteeism. The American Physical Therapy Association's guidelines on neck pain recommends utilizing cervical manipulation (CM) and mobilization procedures to reduce neck pain based on strong evidence. Spinal manipulation is defined as "a passive, high velocity, low amplitude thrust applied to a joint complex within its anatomical limit with the intent to restore optimal motion, function, and/or to reduce pain" and its effectiveness, concretely of a continuous program of cervical manipulations (CM), on neck pain has been largely studied. A previous systematic review concluded that treatments based on CM are effective both alone and in combination with exercises whilst other systematic reviews and an evidence-based guideline showed that CM, combined with exercises, resulted to be more effective for neck pain, function, and global perceived effect, than a therapeutic program based, exclusively, on CM.

Nevertheless, the underlying mechanisms of the pain decrease with this therapeutic approach are not completely understood. A recent study aimed at analyzing the biomechanics of a single CM, used a complex system of synchronized biplane radiographs to measure the facet gapping during a single manipulation. Authors demonstrated that target and adjacent motion segments undergo facet joint gapping during a manipulation and that segmental and global range of motion (ROM) increases in all three planes of motion immediately after one manipulation.

In the clinical setting, the best of our knowledge, only one previous clinical trial have analyzed the effectiveness of a single cervical manipulation on cervical range of motion, comparing with placebo, demonstrating an improvement in all the global maximum cervical movements, measured with the goniometer. However, pain may affect other movement' characteristics beside the maximum range of motion (ROM), as velocity, variability or movement harmony.

Nevertheless, no previous study has analyzed the characteristics of the patients' cervical motion pattern after a single manipulation which could provide information about functional changes in cervical movements. People with neck pain, has shown more slow movements, less harmonic movements in the points close to pain and exponential trend at the ends of the range, even when cervical spine motion ranges remain within normal limits.

The investigators hypothesized that functional assessment of the cervical spine based on the analysis of the motion pattern, will let us know if a single manipulation is effective in the improvement of those variables.