Ultrasound guidance for intra-articular injections of the foot and ankle.

BACKGROUND: Ultrasound has been increasingly utilized in procedures involving intra-articular injections. This study's purpose was to compare the accuracy of intra-articular injections of the foot and ankle using palpation versus dynamic ultrasound in a cadaver model.
MATERIALS AND METHODS: Fourteen lightly embalmed cadaver specimens without notable osteoarthritis were used. A 0.22-gauge needle was placed by a foot and ankle orthopaedic surgeon into the first and second tarsometatarsal joints, subtalar joint, and ankle joint. The needle was initially placed using palpation, evaluated with ultrasound by an experienced rheumatologist, and re-inserted if necessary. Needle placement was confirmed with injection of an Omnipaque/methylene blue solution and examined under fluoroscopy, followed by dissection.
RESULTS: Palpation and ultrasound were 100% accurate in subtalar and ankle joint injections. Using palpation, the needle was correctly placed into the first TMT joint in three of 14 cadavers, and in four of 14 cadavers for the second TMT joint. Using ultrasound, the needle was correctly placed into the first TMT joint in ten of 14 cadavers, and into the second TMT joint in eight of 14 cadavers. When grouped, ultrasound was significantly more accurate for intra-articular needle placement compared to palpation in the midfoot (p = 0.003). On three specimens, dye extended beyond the second TMT joint.
CONCLUSION: Intra-articular injections of the subtalar and ankle joints can be successfully performed utilizing palpation alone. Ultrasound guidance significantly increases injection accuracy into the TMT joints compared to palpation alone and therefore US or Fluoroscopy is performed when injecting these TMT joints. When using selective diagnostic injections into a TMT joint to assess for the symptomatic joint and potential need for arthrodesis, the injected anesthetic may not remain isolated within that joint. These isolated TMT injections should not be done to answer that question without fluoroscopy confirmation with radiopaue dye demonstrating the injected fluid remained within the one joint of interest.