Background and Objectives Previous studies have shown the vulnerability of the tips of cutting type thin spinal needles and the possibility of foreign material passing into the subarachnoid space during the lumbar puncture. We made a microscopic analysis to compare two commonly used noncutting pencil-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, modified 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 subarachnoid puncture; 16 needles of each tip design were investigated under a fluorescence microscope, and another 16 needle tips were collected into test tubes and cytocentrifuged smears were prepared. The tips and smears with the 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 frequently seen on modified Quincke needles (56%) compared with modified Sprotte (37%) and Whitacre (37%) needles (NS). In the cytocentrifugation smears, the largest clusters of epithelioid cells and muscle fibers were observed in the Quincke group. In the Whitacre group many fewer and smaller cell clusters including small muscle particles were seen, and only minor epithelioid cells were found in the Sprotte group.

Conclusions Tissue coring seems to be a common phenomenon during lumbar puncture. The most prominent attachments appeared with a cutting Quincke-type spinal needle.