Identification of Epidural Space: A Comparison Study Between Contrast Spread and Loss of Resistance Techniques
Phase: NA
Conditions: Cervical Radiculopathy, Neck Pain, Disc Prolapse With Radiculopathy
Sponsor: Yakov Perper, MD

Study protocol. Statistical analysis and results. 
 
Title: Identification of Epidural Space: A Comparison Study Between Contrast Spread 
and Loss of Resistance Techniques 
 
REB tracking number: 19-06-002 
 
 
Date of document: 07/17/2020 
 
 
 
 
 
 
 
 
 
 

 
 
The study protocol. 
The study participants were patients of Astoria Pain Management, New York, USA (age 
28–72 years) with a clinical diagnosis of cervical radiculitis. The Canadian SHIELD 
Ethics Review Board approved this study (July 18, 2019. REB tracking number: 19-06-
002), conducted from August 19, 2019, to October 8, 2019. Patients were eligible for the 
study if they met the criteria for cervical ESI, which included clinical and recent MRI 
findings confirming the diagnosis of cervical radiculitis and inadequate pain relief with 
conservative care for more than 3 months. Other criteria were if the procedure was 
covered by medical insurance, and if they signed informed consent. Patients were 
excluded from the study if they were taking anticoagulants or had serious comorbidities 
such as congestive heart failure.  
The patients were divided into two groups of 20 each and underwent CESI with either 
an 18G or a 25G Tuohy needle. Patient selection for the18G and 25G groups was not 
random. For example, the preference was given for a 25G needle when the procedure 
was performed at the C5-6 level (25G/18G = 15/4) and for an 18G (18G/25G = 16/5) 
when the needle was inserted at C6-7 or C7-T1 level. The smaller needles were favored 
for females (25G/(25G+18G) = 17/24) vs. males (25G/(25G+18G) = 3/16). The skin was 
anesthetized with 1% lidocaine in the 18G group but not in the 25G group.  All CESIs 
were performed utilizing the fluoroscopy only method when the needle was navigated 
from the skin toward the epidural space under contralateral oblique fluoroscopy, and the 

contrast spread technique was employed for epidural space identification. After 
radiological confirmation of the epidural spread, LOR was tested using an Epidrum® 
device (Exmoor Innovations Ltd., Somerset, UK). Subsequently, accompanied by the 
radiology assistant, I observed the Epidrum for 30 seconds or more; if the Epidrum 
deflated, the result was positive. However, if the device remained inflated, the result 
was reported as negative. The collected data was then analyzed.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 
Statistical analysis and Results. 
 
There were three investigations: 
1) Within group 1; 18G (LORT vs. CST), 
2) Within group 2; 25G (LORT vs. CST); and  
3) Between groups 1 and 2 (LORT 1 vs. LORT 2). 
 
The Confidence Interval Test for Proportion to estimate the confidence interval (CI) 
between LORT and CST within groups 1 and 2 was employed. The 95% CI was [0.385, 
0.815] for group 1 (LORT 60%; 18G) and [-0.031, 0.231] for group 2 (LORT 10%; 25G), 
confirming that LORT showed a statistically significant lower rate of epidural space 
detection than CST within each group (Table 1). 
 
Table 1. The 95% Confidence Interval test for proportions of epidural space detection by 
LORT within 18G and 25G groups. 
 
 
x 
n 
p 
Margin of error for 95% 
CI 
Lower 
Limit 
Upper 
Limit 
LORT 
18G 
12 
20 
60 
0.215 
0.385 
0.815 
LORT 
25G 
2 
20 
10 
0.131 
-0.031 
0.231 
 

Rate of epidural space detection by CST in both groups is 100%. The 95% Confidence Interval 
test for proportions confirmed that epidural space detection by LORT is significantly lower than 
the CST.  x–positive results, n–number of patients, p–percentage of positive results. 
 
The z-test for independent proportions was utilized to compare the epidural space 
detection between LORT 1 (group 1; 18G) and LORT 2 (group 2; 25G). Since CST 
detected 100%, it was employed as a benchmark to conduct a hypothesis test of 
proportion, using H0: ρ = 1; Ha: ρ < 1. There was a statistically significant difference 
between the proportions of epidural space detection by LORT with 18G compared to 
25G needles: z = 3.31, p < 0.001, Cohen's h = 1.13 (Table 2).   
 
Table 2.  Z-test for independent proportions for the difference in the epidural space 
detection by LORT between 18G and 25G groups. 
 
 
x 
n 
p 
LORT 18G 
12 
20 
60 
LORT 25G 
2 
20 
10 
 
Significance 
level 
Pooled 
proportion 
z 
p-value 
Effect size 
Cohen’s h 
0.05 
0.35 
3.31 
0.0009 
1.13 
 
CST=20 (100%) was employed as a benchmark. Since p-value: 0.0009 < 0.05, H0 was rejected. 
As Cohen’s h > 0.8, the difference in LORT detection rate between 18G and 25G needles is 
large.