First metatarsophalangeal joint aspiration using a 29-gauge needle

Objectives: To asses the clinical feasibility of aspirating symptomatic and asymptomatic first metatarsophalangeal (MTP) joints with a 29-gauge needle in order to obtain a synovial fluid (SF) sample. Methods: All consecutive aspirations of first MTP joints performed within our department were prospectively recorded. The procedure was considered successful if SF volume was enough to perform a crystal search. Crystals were identified using a polarised light microscope (magnification x400) with a first order red compensator. Pain was recorded on a 10-cm visual analogue scale (VAS). Results: Aspirations were attempted in 33 first MTP joints in 31 patients. SF was drawn from 30 of the joints (91%), with little difference between asymptomatic (89%) and inflamed joints (93%). The technique was well tolerated (mean VAS 1.74). Urate monosodium crystals were identified in 22 samples (73%) and another sample contained calcium pyrophosphate dihydrate crystals. Conclusions: A 29-gauge needle allows easy aspiration of the first MTP joint with only modest discomfort for the patients, and generally yields a SF sample of sufficient volume for crystal detection and identification.