DOES THE DESIGN OF THE SPROTTE SPINAL NEEDLE REDUCE THE FORCE NEEDED TO DEFORM THE TIP

Study Objective: To determine whether the window design of pencil-poin t spinal needles leads to deformation under lateral or axial loading c onditions. Design: Independent-measure, multigroup study of the force required to deform needles. Setting: Independent testing laboratory. M easurements and Main Results: The force necessary to bend 22- and 24-g auge Sprotte, 22- and 25-gauge Whitacre, and 22- and 25-gauge Quincke needles was measured using an Instron gauge (Instron Corp., Canton, MA ) after microscopic verification of needle uniformity. Effects of late ral and axial forces were evaluated in separate experiments. The force needed to bend the Sprotte needles was less than that needed for the Whitacre and Quincke needles of similar size when lateral or axial pre ssure was applied. Microscopic inspection of the needles showed a mark ed variability in the window area placement in a single lot of Sprotte needles. Examination of the needle tips demonstrated that the Sprotte needles were most likely to bend at the needle window, while the Quin cke and Whitacre needles deformed at the point of clamping. Conclusion s: The Sprotte needles have an inherent design weakness to lateral and axial pressure, which may result in a greater number of needle tip de formations upon needle insertion. The nature of this deformation may r esult in difficulty in needle withdrawal and possibly fracture of the needle tip.