Background and objectives: Needle trauma may cause peripheral nerve injuries during performance of peripheral nerve block.
Methods: Four types of 21-gauge needles for regional anesthesia were compared: a beveled nerve block needle (Quincke type); a short-tapered needle with a side orifice (Whitacre type); a long-tapered needle with a side orifice (Sprotte type); and a long-tapered double needle combining an inner pencil-point fine needle with an outer truncated conical needle (a new type). This new needle was developed to reduce the potential for nerve injury while retaining a suitable flow rate of anesthetic solution and the ability to inject the solution precisely at the point of paresthesia elicited by the tip. Each type of needle was used to produce puncture injuries to rabbit sciatic nerves. Eighteen specimens were studied within each needle group. The beveled needle was used to produce two different types of nerve injuries by inserting it either transverse or longitudinal to the nerve fibers. Each histologic specimen of the nerve with the needle puncture was surface-stained with hematoxylin-eosin and Bodian's method. Subsequently, the number of damaged axons was histomorphologically counted and statistically evaluated.
Results: Both long-tapered needles produced significantly fewer transected axons than the beveled needle inserted with the bevel longitudinal to the nerve fibers.
Conclusions: The long-tapered needles produced the least number of transected nerve fibers after sciatic nerve puncture.