Intra-rater reliability of determining positions of cervical spinous processes and measuring their relative distances: An update to define rigid bodies of the cervical spine in a movement laboratory setting

OBJECTIVES: A reliable detection of bony landmarks of the spine is necessary in order to determine rigid bodies and to reduce the variability of marker placement in a movement laboratory setting. In a first study on the thoracic and lumbar spine, we demonstrated that placing markers on their relative positions between two major landmarks was superior to palpation of specific bony landmarks. The aims of this study were to examine the intra-rater reliability when palpating for spinous processes (SPs) of the second (C2) and seventh cervical vertebrae (C7), to determine the distances between C2 and C7 and the relative position of C7 along the length between C2 and the posterior superior iliac spine (PSIS) level. RESULTS: The intra-rater reliability in determining the distance between C2 and C7 was found to be substantial, with an intra-rater reliability of 0.75 (95% confidence limits 0.55–0.99) and a standard error of the measurement of 0.34 cm. The relative distance of C7 along the total C2–PSIS length was estimated to be 11.5%. The determination of the relative positions of spinal landmarks through measurement is considered superior to their palpation, because it relies on a reproducible and comparable definition of rigid bodies.