Postero-anterior movements of the cervical spine: repeatability of force displacement curves.

The repeatability of instrumented assessments of postero-anterior (PA) movements has been reported previously for lumbar and thoracic spines, but only in relation to limited parameters of the movement. This study describes a device for measuring PA movements of the cervical spine and reports on repeatability of the entire force/displacement (FD) curves. Repeatability was assessed using coefficients of multiple determination (CMDs) and adjusted CMDs (where the mean offset between the two curves are removed and the shape of the curve can be more directly assessed) for inter-rater intra-day (inter-rater), intra-rater inter-day (inter-day) and intra-rater intra-day (intra-rater) repeated measurements. The mean CMD and mean adjusted CMD for intra-rater measurements (0.90 and 0.99, respectively) were significantly higher than for the other measurement intervals. Inter-rater and inter-day mean CMDs were 0.76 and 0.73 and mean adjusted CMDs were 0.96 and 0.97. It is concluded that the maximum repeatability is achieved if the same operator reassesses the patient on the same day. It is hoped that the methodology described will form the basis for further research that will enable greater understanding of what characteristics of PA movements inform manual palpation and thereby enable improvement in both manual therapy treatment teaching efficiency of manual therapy skills.