A MICROSCOPIC ANALYSIS OF CUT-BEVEL VERSUS PENCIL-POINT SPINAL NEEDLES

An in vitro examination of 25-gauge Quincke and 25-gauge and 27-gauge Whitacre spinal needles was performed after insertion in 210 consentin g adult patients. In addition, 300 unused Quincke needles and 300 unus ed pencil-point needles were examined under a dissecting microscope. W hen the microscopic evaluation was performed on the needles after spin al blockade, burrs or blunting of the needle tip were noted in 24% of the Quincke needles compared with only 3% of the 25-gauge Whitacre nee dles and 10% of the 27-gauge Whitacre (P < 0.05). Bony contact with 25 -gauge Quincke and 27-gauge Whitacre needles resulted in an increased incidence of microscopic tip damage (versus 25-gauge Whitacre). Needle -tip damage with the Whitacre needles was limited to blunting of the t ip. The analysis of unused needles revealed significant differences am ong manufacturers of the cut-bevel needles with respect to stylet-to-n eedle length and burrs on the end of the stylet. The leading edge of t he stylet protruded beyond the opening of the needle tip in 7% of the Quincke needles. However, only minor needle-tip abnormalities were not ed with the pencil-point needles (i.e., variability in the side-port o pening to needle tip distance, side-port opening integrity). In conclu sion, bony contact produced more damage to the cut-bevel than to the p encil-point needle tips. In addition, fewer inherent manufacturing def ects were noted with the pencil-point versus cut-bevel needles. Implic ations: It has been suggested that damaged needle tips may contribute to a higher incidence of headaches after spinal anesthesia. A microsco pic examination revealed that the pencil-point (versus cut-bevel) need les had fewer manufacturing flaws and were less susceptible to tip dam age when bony contact occurred during the placement of the spinal need le.