Background and Goal of Study: To identify the anatomical landmarks for successful spinal block, it may be a challenge and inaccurate in some patients. Therefore, this case-control clinical study was conducted. The ultrasound imaging was used to compare between the maximum spinal processes interspace width during the sitting position on either a flat operating table or after inducing 30 0 lateral tilt towards the operating anesthetist.
Materials and Methods: Thirty four adult volunteers were enrolled in this study. Exclusion criteria were participants under 18 years, pregnancy, body mass index less than 25 and inability to maintain sitting position for spinal anesthesia. The maximum interspinous space width at L4-L5 and L5-S1 levels (the distant between the relevant two successive spinous processes) was measured during the sitting position while the operating table was manipulated to be either in the flat classical pose or inducing 30 degrees lateral tilt towards the anesthetist. The measurement was performed using the Sonosite ultrasound machine in mms. All ultrasound images were reviewed and confirmed with an experienced radiologist.
Results and Discussion: There were significant increases in the spaces between L5-S1 and L4-L5 spinous processes (P < 0.001); with a mean change of 21% at L5-S1 and 35.4% at L4-L5 spaces. This increase had a strong positive correlation to the independent space itself (P < 0.001 with L5-S1 and 0.002 with L4-L5 spaces). The amount of changes at each level was not significantly correlated to the height and waist circumference of the participants. In the present study, the authors focused on changing the table position and not patient's position by tilting the table 30 degree towards the anesthetist while the patient is in sitting position which pushed the patient to lean forward involuntary to protect himself from falling; (patient was supported by an assistant and protected from falling); and this action lead to widening of the lower lumber vertebral interspace and relaxed the para-spinal muscles.
Conclusion(s): Thirty degrees lateral tilt of the operating table towards the anesthetist during sitting positioning for spinal anesthesia is a feasible technique to widen the intervertebral space which may ease the access to epidural and subarachnoid space.