Cervical spine segmental vertebral motion in healthy volunteers feigning restriction of neck flexion and extension.

The purpose of this study was to obtain comparative data concerning the percentage contribution of segmental cervical vertebral motion to the cervical range of motion (ROM) in healthy volunteers under two conditions: (1) normal, voluntary neck flexion and extension and (2) feigned restriction of neck flexion and extension. Each healthy subject's angular motion over forward cervical flexion and extension was measured first by X-ray analysis during normal, voluntary motion. Then the subjects were asked to pretend that they had a 50% restricted neck range due to pain or stiffness and thus to move in both flexion and extension only as far as about 50% of their normal range. A total of 26 healthy subjects (ten males and sixteen females, age 28.7+/-7.7 years) participated. The total angular motion from C2 to C7 was normal in the unrestricted condition and was significantly reduced in the feigned restriction condition (p<0.001). The percentage contribution of each of the functional units C2-C3 to C6-C7 to this rotation was different between the normal unrestricted and the feigned restricted conditions. In the feigned restricted neck flexion and extension, a shift occurred in the pattern of how each segment contributes to the total angular range. A greater percentage contribution was made by C2-C3 and C3-C4 than under normal conditions (P<0.01), and the percentage contribution to total rotation made by C6-C7 became much less under the feigned restricted movements than under normal, unrestricted neck range (p<0.001). Thus, simulated or feigned restricted neck ROM affects the percentage contribution of the functional units C2-C3 to C6-C7 by showing a higher percentage contribution of the upper cervical segments and less contribution to the angular rotation by the lowest cervical segment. Feigners of restricted neck range thus produce a pattern different from nonfeigning subjects.