Cervical sagittal range-of-motion analysis using three methods: Cervical range-of-motion device, 3space, and radiography

Abstract

Study Design. Cervical flexion, extension, protrusion, and retraction were comparatively measured in volunteers using a cervical range-of-motion device (Performance Attainment Associates, Roseville, MN), a 3space system (Polhemus, Colchester, VT), and lateral radiographs. Objectives. To compare the outcomes of three methods of measurement of cervical flexion, extension, protrusion, and retraction. Summary of Background Data. Few studies compare cervical range-of-motion measurement devices with radiographic measurements, and no studies have compared methods of measurement for cervical protrusion and retraction measurement. Methods. In 20 asymptomatic volunteers, four end- range sagittal cervical positions (flexion, extension, protrusion, and retraction) were measured simultaneously using a cervical range-of-motion device, a 3Space and lateral cervical radiographs. Measurements were compared, and differences were analyzed. Results. There were no significant differences for flexion and extension measurements between the cervical range-of-motion device and that radiographic angle determined by an occipital line and the vertical, nor were there any between the 3Space and that radiographic angle between this same occipital line and C7. The cervical range-of-motion device and the 3Space measurements for flexion and extension, however, differed significantly from one another (P < 0.05). For protrusion and retraction, there was no significant difference between the 3Space and radiographic measurements, but these two both differed significantly from the cervical range-of-motion device (P < 0.05). Conclusions. Available methods of measurement differ as to whether the cervical spine is isolated or includes upper thoracic motion. Protrusion and retraction can be measured reliably with all three methods studied, but without measurement consistency between devices. Because end-range cervical flexion and extension cannot occur in isolation from upper thoracic motion, true cervical motion can be measured only with an internally referenced, or landmark-based, methodology such as the 3Space. Even though the cervical range-of-motion device cannot measure isolated cervical flexion end extension, it is nevertheless a reliable clinical tool in measuring flexion and extension as well as protrusion and retraction as long as patient thoracic positioning is standardized to minimize the upper thoracic contribution.