Objective To explore the needle insertion parameters of deep acupuncture at Baliao points for clinic and teaching.Methods A retrospective analysis of 100 cases of prone pelvic CT from January to June 2016 in Nanjing Hospital was carried out.The 3 Dimages were scanned with continuous 5 mm slice thickness.The optimum needle angle is defined as the angle of the needle along the central axis of sacral anterior and posterior hole

and the angle between the needle body and the skin surface and the center line of the body was observed.The effect needle depth is defined as the thickness of the sacral back soft tissue plus 1/2 sacral depth

to observe the best needle angle of deep acupuncture parameters of Baliao points.Results For deep acupuncture at Baliao

the oblique thorn method should be used with the needle-point toward the inner bottom.The best insertion angle between needle body and skin surface is:Shangliao(BL 31)(61.04±12.15)°

Ciliao(BL 32)(57.57±10.01)°

Zhongliao(BL 33)(58.25±8.69)°

Xialiao(BL 34)(54.39±10.94)°.The optimum angle of insertion between the needle body and the posterior midline of the human body is:BL 31(24.54±6.21)°

BL 32(18.58±7.76)°

BL 33(17.36±7.90)°

BL 34(30.73±9.45)°.The effective insertion depth show a decreasing trend:BL 31(58.16±12.43)mm

BL 32(44.57±11.55)mm

BL 33(33.96±10.74)mm

BL 34(31.13±10.94)mm.The effective depth is positively correlated with BMI

and has no correlation with gender and weight.Conclusion The study of the parameters of needle insertion should be taken into account both clinical efficacy and safety

and CT three-dimensional reconstruction can accurately

rationally and scientifically perform acupoint anatomical measurements.