ABSTRACT
<p><b>OBJECTIVE</b>It is unknown whether the psoas major muscle, thought to be a key muscle for treatment of lower back pain, can be punctured at Shenshu (BL23).</p><p><b>METHODS</b>Twelve dissected specimens were used for studying the needling pathway of BL23 by perpendicularly inserting the depth-measuring blade of a vernier caliper at BL23. Dimensions of psoas muscle were measured. Correlation studies were conducted. In addition, our samples were grouped by gender and underlying medical conditions for analysis.</p><p><b>RESULTS</b>Half (50%) of the needle insertions successfully punctured psoas muscle. The mean depth of needle insertion to puncture psoas muscle (Dmin) in the group with short-term underlying medical conditions was 38.0 mm (interquartile range 29.0-51.8 mm), approximately 6 mm deeper than 32.0 (29.3-42.5) mm in the group with long-term health problems (P = 0.041). The cross-sectional area (CSA) of psoas muscle in the former group was on average approximately 1.5 times that of the latter group (P = 0.04). When the data were analysed by gender, the thickness of psoas muscle in the male group was 19.0 (6.5-24.0) mm compared to 19.5 (5.8-34.8) mm in the female group (P = 0.02). The age in the female group (P = 0.04) and the body length of the total group (P =0.04) negatively correlated to Dmin.</p><p><b>CONCLUSION</b>Needle insertion at BL23 might be able to puncture psoas muscle. Differences in the CSA of psoas muscle and Dmin were observed in groups with short-term and long-term underlying medical conditions.</p>