Microscopic analysis of three different spinal needle tips after experimental subarachnoid puncture

Background and Objectives: Previous studies have shown the vulnerability of the tips of cutting type thin spinal needles and the possibility of foreig n material passing into the subarachnoid space during the lumbar puncture. We made a microscopic analysis to compare two commonly used noncutting penc il-point spinal needles with different tip designs. Needles with a cutting tip design were included as reference. Methods: Four fresh cadavers were placed in the lateral position and their backs were scrubbed with disinfectant solution containing 0.1% fluorescein. Thirty-two spinal needles (27 gauge) of each type (modified Quincke, modif ied Sprotte, and modified Whitacre) were inserted through an introducer at interspaces L2-5 into the subarachnoid space. Under visual control (spinal canal opened ventrally) all the needle tips were cut after successful subar achnoid puncture; 16 needles of each tip design were investigated under a f luorescence microscope, and another 16 needle tips were collected into test tubes and cytocentrifuged smears were prepared. The tips and smears with t he most obvious findings were photographed under a microscope. Results: On microscopy, only 2 needle tips were damaged (1 modified Quincke and 1 modified Whitacre). Visible fluorescent tissue particles were more f requently seen on modified Quincke needles (56%) compared with modified Spr otte (37%) and Whitacre (37%) needles (NS). In the cytocentrifugation smear s, the largest clusters of epithelioid cells and muscle fibers were observe d in the Quincke group. In the Whitacre group many fewer and smaller cell c lusters including small muscle particles were seen, and only minor epitheli oid cells were found in the Sprotte group. Conclusions: Tissue coring seems to be a common phenomenon during lumbar pu ncture. The most prominent attachments appeared with a cutting Quincke-type spinal needle.