Background Ultrasound (US) is widely used in rheumatology to study and guide infiltration of peripheral joints. This imaging modality can also provide useful information about the anatomy of the lumbar spine. Studies have shown that US examination of the spine was an useful tool to help perform epidural anesthesia .
Objectives To determine if the identification of the optimum puncture level by a pre-puncture US examination of the lumbar spine may facilitate epidural corticosteroid injection in patients with a presumed difficult puncture.
Methods We performed a prospective randomized single-blind controlled study (NCT01832844). All patients referred to our unit for the treatment of sciatica due to lumbar disc herniation were evaluated. Inclusion criteria were a BMI >30 kg/m2 and/or age >60 years and/or lumbar scoliosis (Cobb angle >10°). Patients were randomized to a US (n=40) or a control (n=40) group. The US group underwent a pre-procedure spinal US (Esaote Mylab 70; 3-11 MHz probe). Interspinous spaces and depth of the epidural space were measured. Visibility and accessibility of the epidural space was thus rated as “poor”, “moderate” or “good”. The best lumbar level to perform the injection was selected according these results. Patients of the control group underwent a fake US examination to remain blind to the group allocation and the level of injection was selected using the traditional landmark technique. An interspinous injection of 5 ml of Hydrocortisone was thus performed. Primary endpoint was the pain during the procedure assessed using the Visual Analogue Scale (VAS). Each redirection of the needle was counted. Data are presented as the mean (±SD). A Student t-test and a Pearson correlation test were used for the statistical analysis.
Results Mean age was 62,5 (±16) and 33% were men. 47/80 (58%) patients were over 60 years, 41/80 (51%) had a BMI>30 kg/m2 and 14/80 (17%) had a lumbar scoliosis. Among the 80 patients, 21 (26%) had 2 or more criteria of presumed difficult puncture. Mean epidural space depth was 49.2 mm (±13.8) and mean interspinous distance was 14.22 mm (±5.1). We found a positive correlation between epidural space depth and BMI (p<0,001) and a negative correlation between interspinous spaces and age (p<0,01). A reduction of the intensity of pain during the procedure was observed in the US group compared to the control group (mean VAS 2,01±1,6 versus 2,95±2,5 respectively; p=0,05). The difference was even greater in patients over 60 years (mean VAS 1,86±0,4 versus 3,50±0,4; p=0,08). Finally, 22/40 (55%) injections were performed without any redirection in the US group compared with 16/40 (40%) in the control group (p=NS).
Conclusions US evaluation of the interspinous space and epidural depth is feasible even in obese or old patients. Identification of the optimum puncture level by a pre-puncture US decreased the pain during the epidural injection procedure. This benefit was greater in patients over 60 years. US of the lumbar spine represents an additional technique at the rheumatologist's disposal to help guiding lumbar spine injections.
Grau T, Leipold RW, Conradi R, et al. Efficacy of ultrasound imaging in obstetric epidural anesthesia. J Clin Anesth. 2002;14:169-75.
Disclosure of Interest : None declared