First Metatarsophalangeal Joint Injection
Pain at the base of the first metatarsophalangeal joint (MTP), also known as the big toe, can be due to a variety of conditions. Aspiration of this joint is frequently performed to help differentiate between rheumatoid or osteoarthritis, and crystal-induced arthropathies (e.g., gout or pseudogout).
Obtain informed consent from the patient.
Gather appropriate materials needed for the procedure.
First, draw up 1cc of 1 or 2% lidocaine into a 3-5cc syringe.
Then draw up the steroid into the same syringe in order to intermix the two together.* You may use this list of four commonly used steroids as a reference.
*If you are planning to aspirate:
Use a larger syringe (e.g., 10cc) to draw up your anesthetic.
Draw up the steroid in a separate syringe to inject after the aspiration is complete.
Have the patient lie supine with their legs extended. It is a good idea to stabilize the lower extremity by placing a towel roll or gown, as shown, beneath the knee.
Make sure the exam table is long enough to support the patient's foot.
In this image: The patient lies supine on an exam table that is long enough to support their foot.
Ask the patient to flex and extend the toe to assess the location of the joint line. Using your index finger and thumb, palpate the joint line as you passively flex the toe.
Cleanse the skin with povidone-iodine or an alcohol swab.
In this image: The physician has marked the MTP joint.
Using a 25-gauge, 1-inch needle, insert the needle from the medial surface, perpendicular to the skin.
Direct the needle laterally. Valgus traction may be applied to the distal phalanx to open up the joint space.
If aspirating, draw off the fluid necessary for laboratory evaluation. Remove the syringe containing the synovial fluid and steady the needle hub (it is optional to use a sterile hemostat for this step). Replace the syringe used to aspirate with the steroid-containing syringe, then inject. Remember, do not inject steroids if you suspect a septic joint.
