Spatial profiles of acupoint use across the distal–proximal Five-Shu sequence

Acupuncture treatment typically involves the coordinated selection of multiple acupoints across the body; however, the spatial organization of their use remains poorly understood. Variation across the distal–proximal ordering of limb acupoints may provide a useful basis for examining acupoint selection. The Five-Shu system offers a structured model for testing this possibility, yet it remains unclear how its categorical sequence relates to the anatomical spacing of the corresponding acupoints. We mapped Five-Shu acupoint usage and recommended needling depth onto standardized ordinal coordinates. This categorical order differed from the physical spacing of the corresponding points. Selection frequency peaked at intermediate positions in Yin meridians but shifted proximally in Yang meridians, whereas recommended depth generally increased proximally. Usage and depth profiles aligned closely in Yin meridians but diverged in Yang meridians. These findings suggest that acupoint selection varies systematically across the Five-Shu system, supporting the use of the Five-Shu sequence as an ordinal analytical framework that should not be interpreted as an equally spaced anatomical model.