. Author manuscript; available in PMC: 2009 Jul 25.

Published in final edited form as: Reg Anesth Pain Med. 2009;34(2):100–105. doi: 10.1097/AAP.0b013e31819a12ba

TABLE 2.

Needle Depth and Fluoroscopic Oblique Angle by Body Mass Index Category

	Underweight (n = 1)	Normal (n = 16)	Preobese (n = 26)	Obese Class I (n = 22)	Obese Class II (n = 15)	Obese Class III (n = 6)
Needle depth, median (interquartile range), cm	6.3	7.5 (7.0–8.5)	8.4 (8.0–9.5)	10 (8.9–12.5)^*	10.4 (9.3–11.8)^†	12.2 (12–12.5)^‡
Oblique angle, mean (SD, min-max), degrees	15 (—; 15–15)	35 (8.4; 20–50)	29.23 (8.5; 12–47)	33.8 (9.7; 15–50)	28.72 (8.2; 15–47)	32.0 (3.9; 27–35)

BMI categories based on classifications by the World Health Organization.²³

Obese class I patients (BMI, 30–34.99 kg/m²) required a significantly increased depth (P < 0.01) when compared with normal patients (BMI, <25 kg/m²).

^†

Obese class II (morbid obesity) (BMI, 35–39.99 kg/m²) required a significantly increased depth (P < 0.01) when compared with normal and overweight patients.

^‡

Obese III (super-morbid obesity) (BMI, >40 kg/m²) was associated with an increased depth (P < 0.01) when compared with normal, overweight, and obese patients.