Cervical flexion, extension, protrusion, and retraction. A radiographic segmental analysis

A lateral radiographic analysis of the cervical spine was performed on 20 asymptomatic volunteers.

To quantify the contribution of each cervical segment to each of four sagittal cervical end-range positions: full-length flexion, full-length extension, protrusion, and retraction.

Recent clinical research supports the relevance of cervical protrusion and retraction in symptomatic patients. Currently, few quantitative studies are available regarding cervical protrusion and retraction.

Lateral cervical radiographs of 20 asymptomatic volunteers for four test positions and a neutral position were collected. Mean angular measurements and available ranges of motion were calculated from the occiput to C7.

Retraction consists of lower cervical extension and upper cervical flexion, whereas protrusion consists of lower cervical flexion and upper cervical extension. Full-length cervical flexion produced more flexion at lower segments than did protrusion, and full-length cervical extension produced more extension at lower segments than did retraction. With both full-length flexion and retraction, upper cervical segments are positioned in the flexion portion of their total range, but only retraction takes Occ-C1 and C1-C2 to their full end-range of flexion. Similarly, with both full-length extension and protrusion, upper cervical segments are positioned in the extension portion of their total range, but only protrusion takes Occ-C1 and C1-C2 to their end-range of extension.

A greater range of motion at Occ-C1 and C1-C2 was found for the protruded and retracted positions compared with the full-length flexion and full-length extension positions. Effects on cervical symptoms reported to occur in response to flexion, extension, protrusion, and retraction test movements may correspond with the position of lower cervical segments.