Functional roentgenometric evaluation of the cervical spine in the sagittal plane.

Neutral, flexed and extended lateral cervical radiographs were taken of sixteen male and fourteen female asymptomatic subjects and were evaluated in order to determine the amplitude of sagittal motion occurring intersegmentally. Using templates, the quantity of vertebral body displacement was expressed as a percentage ratio. Statistical analysis provided a radiographic definition of a normal range of intersegmental motion, hypomobility, articular fixation, hypermobility and instability. Other quantitative features of sagittal plane motion are discussed. Absolute hyper and hypomobility is defined by motion (% SBD) values falling between one and two standard deviations above normal (.60 to .72 and .38 to .26, respectively). Values greater than two standard deviations above normal were found to represent instability and functional blockage (greater than .72 and less than .26, respectively).