BACKGROUND: The aim of this study was to investigate whether needles introduce skin plugs into joints during arthrocentesis.

MATERIAL AND METHODS: In the first part of this study, the arthrocentesis site was scrubbed with a fluorescein sodium swab, and 90 needles were inserted through the joint tissue and collected for examination under a fluorescence microscope. In the second part of this study, the joints were injected using 720 needles of different gauges. Two different randomly assigned needle insertion techniques were used: needle insertion straight through the joint capsule (subgroup 1) or insertion of the needle into the subcutaneous tissue followed by flushing of the needle with 0.5 mL of 0.9% normal saline prior to advancing the needle through the joint capsule (subgroup 2).

RESULTS: Of the 90 needle tips examined in the first part of this study, 21 had high-grade fluorescein contamination. In the second part of this study, the incidence of tissue, epidermis, and dermis contamination in subgroup 1 was 57.2%, 43.1%, and 25.0%, respectively. There was no significant difference in the incidence among different gauge needles, except for a difference in epidermis contamination between the 21-gauge and 23-gauge needles. Compared to subgroup 1, subgroup 2 had a significantly lower OR for tissue contamination.

CONCLUSIONS: It is common to introduce tissue coring with epidermis and dermis into the joint during arthrocentesis, which poses a potential risk for septic arthritis. However, tissue contamination of the joint may be reduced by flushing saline through the needle into the subcutaneous tissues prior to entering the joint capsule.

Keywords: Arthritis, Infectious, Injections, Intra-Articular, Needles