"The Fly": a new clinical assessment and treatment method for deficits of movement control in the cervical spine: reliability and validity.
STUDY DESIGN
Test-retest and case-control study designed to detect accuracy of cervical spine movements by comparing 3 incrementally difficult movement patterns. An asymptomatic group, a nontrauma neck pain group, and a group with whiplash-associated disorders, Grade II, were tested (n = 18 in each group).


OBJECTIVE
To determine the test-retest reliability and the discriminative validity of the new Fly method.


SUMMARY OF BACKGROUND DATA
A lack of reliable and valid measures for grading the deficits of movement control in the cervical spine makes it impossible to prescribe treatment appropriate to each patient's respective impairment level.


METHODS
Head tracking of a moving fly which appeared on a computer screen. Easy, medium, and difficult patterns, each of which was repeated 3 times in random order, were tested. Amplitude accuracy (deviation of movements), directional accuracy (time on target, undershoots vs. overshoots) were compared across patterns and groups on 2 occasions, 1 week apart.


RESULTS
The intraclass correlation coefficient(2,1) ranged from 0.53 to 0.82 for both variables, except for the subvariable "overshoots" (0.14-0.42). The limits of agreement (LOA) were progressively wider across patterns (easy-medium-difficult) and groups (asymptomatic-nontrauma-whiplash-associated disorder). Analysis of variance with repeated measures revealed significant differences between patterns within each group and between groups respectively for both outcome variables (P < 0.001).


CONCLUSION
The Fly method provides reliable and valid measures for movement control of the cervical spine. Higher means and wider LOA across patterns and subject groups are reasoned to be inherent in the new Fly method and the subject groups tested. The wide LOA in the symptomatic groups supports the development of a normative database. The new Fly method can be used both as an assessment and a treatment method and ensures gradual progression in the treatment for deficits of movement control in patients with neck pain.