Three-dimensional head axis of rotation during tracking movements. A tool for assessing neck neuromechanical function.

The purpose of this article is to report normal variation in the screw (helical) axis of rotation of the head during various types of natural tracking movements. Nine normal subjects and eighteen subjects with neck injury faced a grid of targets separated by 10-degree intervals, and were instructed to use a head pointer (laser) to track whatever target was lit. Various horizontal, vertical, and oblique target sequences were employed. The normal subjects exhibited several consistent trends in finite screw axis parameter variation: vertical movements have a laterally-directed axis whose midsagittal plane crossing position is a function of the head orientation (typical range C3-T1); oblique movements have a diagonally-directed axis and an even greater orientation-specific range (C1-T1); and horizontal movements have a vertical axis that is modified near horizontal orientation extremes and is asymmetrically influenced by upward and downward bias orientations. Subjects with neck injury were seen to exhibit a variety of abnormal screw axis patterns.

Three-dimensional head kinematics and clinical outcome of patients with neck injury treated with spinal manipulative therapy: a pilot study.

OBJECTIVE: Finite helical axis parameters (FHAP) of the cervical spine and clinical measures were obtained to evaluate neck function and the clinical effects of spinal manipulative therapy in patients with "whiplash" (WL) type neck injury. DESIGN: Descriptive case series, 1 yr follow-up. SETTING: Three private chiropractic practices. SUBJECTS: Ten consecutive new patients with a history of neck injury, nine asymptomatic, volunteer controls. INTERVENTIONS: A 6-wk regimen of short lever manually assisted adjustments with an Activator Instrument, while acute, four patients received interferential electrotherapy. MAIN OUTCOME MEASURES: Cervical FHAP during normal movements, neck pain (visual analogue scale), active cervical range of motion and follow-up questionnaire. RESULTS: Based on six patients, the FHAPs appeared to mirror the clinical condition, being markedly deviant from the patterns observed in the control group for at least one or more of the tracking tasks for all but one of the patients. Mean pain scores decreased from 44.1 to 10.5 (t = 4.93; p < .0001) and mean total range of motion increased from 234 to 297 degrees (t = 5.68; p < .0001). At 1 yr, seven respondents noted stability of their symptoms at or near the level reported immediately after the 6-wk treatment period. CONCLUSIONS: Based on these preliminary data: a) FHAPs may aid in diagnosing and monitoring treatment of neck dysfunction, b) spinal manipulative therapy may be beneficial to some patients with neck injury and future study is warranted as a means to promote recovery of patients with neck injuries.