Comparison of needle deviation during regional anesthetic techniques in a laboratory model

Although many characteristics of needles used for spinal and epidural anesthesia have been studied extensively, the amount that a needle deviates from a straight path while passing through tissue has been relatively ignored. A laboratory model was used to determine the amount of needle deviation produced when different types of new spinal needles and epidural needles were passed through porcine tissue. Both needle point design and, to a lesser extent, needle gauge were found to influence the amount and direction of needle deviation. Deviation was found to be the least for the pencil-point spinal needles (Whitacre, Sprotte, Safetap, range 0.60-1.00 mm/50 mm tissue, analysis of variance (ANOVA) P < 0.001). Needles commonly used for epidural anesthesia (Tuohy, Hustead, Crawford) exhibited increased deviation (range 1.73-3.54 mm/50 mm tissue), although the largest amount was seen with beveled spinal needles (Quincke, Atraucan) (range 4.42-5.90 mm/50 mm tissue). The possible clinical significance of needle deviation during the performance of a regional anesthetic is discussed.