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Thursday, March 1, 2001

Injection in joint may introduce inflections

A study of intraarticular injections using standard needles demonstrates that introduction of skin into the knee joint is common.

There is potential for introduction of infectious agents injected with the skin, especially when minimal skin preparation is performed, say coauthors of scientific paper 60, presented Wednesday. They advise that in addition to meticulous skin preparation, reduction in the needle gauge used and aspiration into a separate syringe prior to injection through the needle, may reduce risk. The study coauthors say that "a feared complication of arthrocentesis is the introduction of infectious material into the joint space. While postinjection overt bacterial arthritis is considered to be rare, it does occur, and it is not clear that a low-grade infection may be more common."

To confirm placement of the medial portal during arthroscopy, a spinal needle is routinely introduced and inspected upon penetrating the joint capsule. A prospective study was designed to observe the presence of skin material using various spinal needles with and without a stylus. Specimens were recovered and analyzed histologically and with polymerase chain reaction (PCR). The study included 112 patients.

The investigators compared 18 and 25 gauge needles each with fully inserted stylus or with partially inserted stylus. In patients with a partially inserted stylus, it was fully inserted after passing into the joint space. At surgery, surface anatomy was marked using a surgical marking pen, staining the skin at the entry. A positive result was defined as the visualization of blue colored tissue on the needle bevel.

With the stylus fully inserted into an 18g needle, 100 percent of needle insertions produced identifiable skin fragments ranging in size from trace to 3mm. With the stylus partially inserted into an 18g needle, 100 percent of trials also produced positive results. However, in 76 percent, the skin remained in the needle shank and was only identified with full insertion. With a 25g needle with stylus fully inserted, 74 percent of trials produced positive results with smaller sized fragments. With the stylus partially inserted into a 25g needle, 88 percent of trials produced positive results.

The specimens, which were evaluated using light microscopy, confirmed the presence of skin. Among the six specimens evaluated with PCR, two had evidence of bacterial nucleic acids.

Coauthors of the study are David L. Glaser, MD; Arthur R. Bartolozzi, MD; Jeffrey C. Schildhorn, BS, Rita Denis, RN; Yong Li, MS; and H. Ralph. Schumacher, MD, all of Philadelphia, Pa.

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2001 Academy News March 1 Index C

Last modified 14/February/2001 by IS