An Exploration of the Needling Depth in Acupuncture: The Safe Needling Depth and the Needling Depth of Clinical Efficacy

Table 5

Summary of researches using dissected specimens of cadavers for measurement of the depths of acupuncture points.

Authors and year	Subjects and sample size	Investigated acupuncture points and their body regions/meridians	Parameters used in comparison and related factors	Results, suggestions, and conclusions
Oh et al. 2012 [80]	4 adult cadavers	PC6	—	(1) The acupuncture needle should not be inserted deeply at PC6 in order to minimise the risk of trauma; (2) It seemed likely that various kinds of noninvasive stimulation at PC6 may be similarly effective as needling; (3) Careful insertion of the needle with respect to patients’ sensations and better anatomical knowledge of the forearm can help to prevent unexpected needle penetration of the median nerve or persistent median artery
Wang et al. 2009 [81]	15 adult cadavers	ST7, SI18	Side	(1) No side difference; (2) Mean inserting depth of ST7 and SI18 to sphenopalatine ganglion were 49.9 and 46.6 mm
Xie et al. 2007 [82]	46 adult cadavers	SI14 and GV14	Gender	(1) No gender difference; (2) The mean dangerous depth for perpendicular insertion was 60.60 mm for SI14 and 55.93 mm for GV14.; (3) Suggested depth for perpendicular needling of SI14 and GV14 was within 42 mm in adult
Chen et al. 2007 [83]	46 cadavers	CV22, ST11	—	(1) The needle not only easily injuried the upper pleural cavity but also damaged the big blood vessel, the vagus nerve in the mediastinum and the cervical root; (2) The safety depth of ST11 ranged 23.7–52.8 mm
Xie et al. 2006 [84]	46 cadavers	ST12	Gender, side	(1) No gender or side difference; (2) The mean dangerous depth of male was 34.97 mm and female 31.41 mm; (3) The depth for perpendicular needling of SI12 is within 22.50 mm
Xie et al. 2006 [85]	46 cadavers	BL12, BL13	Gender, angles of needle insertion (15, 20, 25, 30, and 40 degrees)	(1) The mean dangerous depth for perpendicular insertion was 49.51 mm of BL12 and 44.88 mm of BL13; (2) It was safe for oblique insertion toward the medial of chest in an angle exceeding 20 degrees; (3) No gender difference
Xu et al. 2006 [86]	48 adult cadavers	BL1	—	(1) The mean depth between the skin and the anterior ethmoidal artery was 18.25±4.45 mm, with an angle of 12.5±5.5 degrees; (2) The depth from the skin to the optic nerve tunnel frontal point was 43.37±7.84 mm; (3) Needling depth should not exceed 30.36 mm (70% of measured depth) to avoid injury of the optic nerve
Lou et al. 2006 [87]	80 limbs (40 cadavers)	ST36	Angle	(1) Average depth was 2.22 cm; (2) Maximal depth was 4.42 cm if needled obliquely; (3) Safe depth was generally less than 5 cm
Chen et al. 2006 [88]	46 cadavers	CV22, ST11, ST12, GB21, EX-B1, and BL11	—	(1) Risk of pleural injury may existed when inserting needle perpendicularly in these points; (2) Divergence existed in observed needling depths such as 22.5–61.3 mm for ST12
Dong et al. 2004 [26]	32 adults and 10 cadavers	7 points from bladder meridian (2nd side line)	Rohrer index: <1.2, 1.2–1.5, and >1.5, side	(1) No side difference; (2) Depths from in vivo CT images were greater than ones from cadavers; (3) Safe depth should be less than 70% of dangerous depth
Li et al. 2004 [27]	32 adults and 10 cadavers	7 points from bladder meridian (1st side line)	Rohrer index: <1.2, 1.2–1.5, and >1.5, side, and needling angles	(1) No side difference; (2) Depths from in vivo CT images were greater than ones from cadavers; (3) Safe depth should be less than 70% of dangerous depth; (4) Safe needling angle should be 10 degrees more than dangerous angle
Yan et al. 2004 [89]	51 cadavers	74 points from neck, chest, back, and abdomen	Angles of insertion	(1) Safe depth should be less than 70% of dangerous depth; (2) Needling angles were suggested such as 65 degrees rather than perpendicular insertion for points in the bladder meridian
Zhang et al. 2001 [90]	51 cadavers	17 acupoints of abdomen	Gender, side	(1) The dangerous depth of most abdominal points were similar and within 11–17 mm; (2) KI11 had the greatest depth up to 25 mm (to the urinary bladder) but with divergence in standard error
Zhang et al. 2001 [91]	57 cadavers	ST12	—	(1) The mean dangerous depths for perpendicular insertion downward was 38.34 mm; (2) Safety depth was within 26.83 mm (70% of the dangerous depth)
Piao and Zhong2001 [92]	6 cadavers	B2 (lumbar levels)	different lumbar vertebrae: L1–L5	The depth ranged 4.2–5.75 cm in different lumbar levels with greater depths in lower lumbar levels
Chen et al. 1998 [93]	20 adult cadavers	BL40	Side	(1) Safe depth (from skin to tibial nerve): 15 mm for left side and 16 mm for right side, less than the depth from current used textbook; (2) Depth from skin to deep vein: 35 mm
Ge 1998 [94]	16 cadavers	GV15, GV16	Thumb Tong Shen Cun	Safe depth of GV15 (42.46–55.86 mm) and GV16 (43.46–57.42 mm) correlated with thumb Tong Shen Cun
Zhang et al. 1998 [95]	51 cadavers	Total of 28 acupoints in back and lumbar region	Gender, side	(1) No side difference in dangerous depth except BL17, BL18 for male and BL17 for female; (2) Points of bladder meridian closer to the spine had greater depths. Divergence existed between points; (3) There was no gender/side difference
Zhang et al. 1998 [96]	51 cadavers	23 chest points	Gender, side	(1) The average dangerous depths of 23 chest acupoints were obtained. KI27 had the greatest dangerous depth up to 26 mm. Others ranged from 11.87 to 17.64 mm; (2) Divergence existed between points; (3) There was no gender/side difference; (4) Safe depth should be less than 70% of dangerous depth
Lin 1997 [29]	80 cadavers (including 30 newborns) and 240 adults for safety depth; 300 real subjects for de-qi depth	All back bladder meridian points and chest points	Gender, Tong Shen Cun, BL, BW (normal, over- and underweight) DQ, and AW	(1) Depths were deeper as compared to ancient writings. The depths highly correlated with body thickness and Tong Shen Cun; (2) De-qi depth was related to therapeutic effect; (3) De-qi depths of chest points were greater in females but not in back points
Yan et al. 1996 [97]	51 cadavers	GV16, GV15, GB20, and BL1	Gender, side	(1) The safe depths (80% of the measured depth) were GV16: 40.08 mm, GV15: 38.10 mm, GB20: 39.77 mm, and BL1: 34.25 mm; (2) No gender or side difference