Contamination of joints with tissue debris and hair after arthrocentesis: the effect of needle insertion angle, spinal needle gauge, and insertion of spinal needles with and without a stylet.

OBJECTIVE: To assess fetlock joint contamination with tissue debris and hair after arthrocentesis. STUDY
DESIGN: Experimental. ANIMALS: Fetlock joint tissues (n = 10 horses).
METHODS: Soft tissue flaps including the joint capsule were dissected from the dorsal fetlock joints of 7 anesthetized horses leaving an intact proximal base. Needles inserted through the tissue flaps were flushed into tissue cell culture plates and examined for debris. Studies were repeated on excised fetlock tissue preparations after being stored for 5 days. Variables included gauge and type of needle, insertion of spinal needles with and without a stylet, angle of insertion, length of hair, and ante- and postmortem needle insertion. Tissue fragments collected from 3 horses were cultured for bacteria.
RESULTS: Compared to 20 g disposable needles inserted perpendicularly through unclipped skin, the odds ratios (ORs) for hair contamination were significantly greater for 20 g spinal needles without a stylet, and significantly less for 22 g spinal needles inserted with a stylet and for angled insertion of disposable needles. Tissue contamination OR was significantly less for 20 g spinal needles inserted without a stylet, angled insertion, and clipped hair. Bacteria were isolated from 2.6% of tissue fragments.
CONCLUSIONS: Angled needle insertion reduces joint contamination with tissue and hair. Spinal needles should be inserted with a stylet in place and 22 g spinal needles are preferable to 20 g spinal needles. Joints may be contaminated with bacteria after routine surgical preparation of skin. © Copyright 2012 by The American College of Veterinary Surgeons.