Sensorimotor synchronization in patients with mechanical neck disorders

Background: There lacks knowledge of how patients with chronic persisting mechanical neck disorder (cMND) coordinate their movements. Objective: Analyze kinematic data from people with cMND by extracting vertical trajectories from 3D Qualisys data of the patients' hand. The time between metronome beat and bottle placement were cross-correlated to compare timing accuracy. Design: Cross-sectional case-series. Method: A cyclical overhead reach and grasp task involving lifting bottles from low to high shelves at a pace of 60 bpm tested muscular incoordination. Subjects from a convenience sample were classified by a modified Quebec Task Force Classification. Motion capture imaging and seven channel electromyography was recorded during each patients' trial. Outcome measures include: Neck Disability Index, subjective pain ratings measured by a numeric pain rating scale, and 3D coordinates from motion capture data. The time between metronome beat and bottle placement were cross-correlated to compare timing accuracy (mean percent values, standard deviation [SD]). Two within-subject variables ([1] side: affected vs. unaffected; and [2] posture: sitting vs. standing) were assessed. Results: Seven participants (five females/two male; age mean 46.7, SD 15.21 years) had a mean of 7.25, SD 2.3 in arm pain and 6.38, SD 2.60 in neck pain post trial. Timing accuracies were found while standing (mean 0.84, SD 0.04) but not sitting (mean 0.67 SD 0.16). Numeric pain ratings increased from pre (neck 4.21[1.88]; arm 3.40[2.72]) to post (neck 6.38[2.61], arm 7.25[2.30]) trial. Conclusion: Initial data suggest that patients with persisting cMND have reduced accuracy in timing when coordinating their movement to a paced external event.