Neutral lateral fingertip-to-floor distance can be derived from height

摘要

Spinal mobility is one of the core outcome measures used in axial spondyloarthritis as recommended by the Assessment of SpondyloArthritis international Society (ASAS). Among the commonly used spinal mobility measures, lateral spinal flexion (LSF) is considered to be the most sensitive to change and has therefore been included as one of the domains in the ASAS 5/6 response criteria. LSF is measured as the difference between two marks placed on the thigh, one in a neutral standing position and the other in maximum lateral flexion. Alternatively, LSF can be calculated as the difference in the lateral distances between middle fingertip-to-floor (FTF) in the neutral position (neutral FTF) and middle FTF in maximum latero-flexion (maximum flexion FTF). In this second LSF measurement, it may sometimes erroneously and accidentally happen that only the maximum flexion FTF is recorded. This prohibits calculation of the LSF unless neutral FTF could be obtained by another method. Because neutral FTF is a static measure, we hypothesised that it would be highly correlated with height and it would be possible to derive its value from height.