The purpose of this study is to measure the skin epidural distance(SED) of L3∼4 interspace and to correlate SED with the individual constitutional data of patients such as body-weight, height, abdominal circumference and body mass index(BMI; kg/m2). In this study we examined 120 patients (45 men and 75 women) who had no pathological abnormality in L3∼4 interspace such as herniated disc, spondylolisthesis and spinal stenosis in MRI study, although majority of patients had pathology below this level. The SED was measured under fluoroscopic guide with loss of resistance technique, and we also measured individual constitutional data of patients.

Pearson's correlation analysis of the data showed that there were no correlations of statistical significance between SED and the height, abdominal circumference of the patient (p＞0.01). But there were statistically significant correlations between SED and body-weight as well as BMI (p＜0.0001). Linear regression analysis of these data showed significant correlations between SED and body weight(male r²=0.49, p＜0.0001, y=0.37x⁢18.1; female r²=0.31, p＜0.0001, y=0.18x⁢30.8), BMI(male r²=0.52, p＜0.0001, y=0.89x⁢23.1; female r²=0.35, p＜0.0001, y=0.41x⁢31.6).