Fig 1.
Experimental models of dural puncture with various spinal needles.
(a) Subjective assessment. Participants were asked to randomly puncture the artificial dura mater (PAF) or porcine dura mater (PDM) at different locations using different spinal needles with the stylet in place thorough the needle introducer. The needle hubs were covered with a colored tape to make their original colors and shapes indistinguishable. (b) Objective measurements of puncture resistance forces using the biomechanical testing machine (AG-I; Shimazu Corporation, Kyoto, Japan). The device was equipped with a 10-N load cell unit connected to an analog measurement circuit, and the obtained data were processed through an analog filter before A/D conversion. Samples (4 × 4 cm in size) of either 50 μm PAF or of PDM were mounted with pins on the testing device. The different types of spinal needles were fixed after passing through the 20 G introducer needle and loaded so that the dura mater could be punctured perpendicularly at a constant velocity of 200 mm min-1. Abbreviations: PAF–PA film, PDM–porcine dura mater.
Table 1.
Numerical rating scores of click sensations perceived with different spinal needles.
Table 2.
Numerical rating scores of click sensations perceived with different spinal needles.
Table 3.
Comparison of click sensations (NRS values) among needles.
Fig 2.
Load-displacement curves obtained by punctures of PAF and PDM with different spinal needles.
Values are represented as mean ± SD. Colors represent curves / values for: PAF–blue and PDM–dark orange. Abbreviations: LDTF–largest drop in total force, PAF–PA film, PDM–porcine dura mater.
Fig 3.
Similarity of load-displacement curves analyzed with the Euclidean distance calculation algorithm.
(A) For each spinal needle, the mean values for each point on the load-displacement curve of all data sets were separately calculated for PAF and PDM data, and for the time interval 0 to 1.19 sec. The smallest Euclidean distance between each point on the PAF load-displacement curve to the PDM curve was then assessed by calculating Euclidean distances at set intervals (0–30 steps backwards) on the time axis. (B) The smallest distances (reflecting closest similarity between the PAF and PDM curves) for a given needle were compared to the distances obtained from calculations of the smallest distances between the PAF curve of that needle and those on the PDM curves of other needles.
Fig 4.
Forces elicited on the spinal needle upon puncture of the dura mater.
(a) Before puncture. The force acting on the needle is due to the elastic deformation of the membrane which is represented as Felastic. (b) After the puncture, Fresistive is added to represent the forces produced by membrane viscosity, similar to frictional forces.