(See also Evaluation of the Patient with Joint Symptoms Evaluation of the Patient With Joint Symptoms Some musculoskeletal disorders affect primarily the joints, causing arthritis. Others affect primarily the bones (eg, fractures, Paget disease of bone, tumors), muscles or other extra-articular... read more and see Evaluation of the Foot Evaluation of the Foot An evaluation of the foot includes a physical examination and sometimes arthrocentesis (see How To Do Metatarsophalangeal Joint Arthrocentesis). (See also Evaluation of the Patient With Joint... read more .)
Diagnosis of the cause of a synovial effusion (eg, infection Acute Infectious Arthritis Acute infectious (septic) arthritis is a joint infection that evolves over hours or days. The infection resides in synovial or periarticular tissues and is usually bacterial—in younger adults... read more , crystal-induced arthritis Overview of Crystal-Induced Arthritides Arthritis can result from intra-articular deposition of crystals: Monosodium urate Calcium pyrophosphate dihydrate Basic calcium phosphate (apatite) Rarely, others such as calcium oxalate crystals read more )
Removal of a synovial effusion and/or injection of drugs as part of treatment and for pain relief
Infection of skin or deeper tissues at the anticipated site of needle insertion
If possible, an alternate, uninfected site should be used. However, acutely inflamed joints may be generally warm, tender, and red, thus mimicking extra-articular infection and making it hard to find an uninvolved insertion site. Ultrasonography can be done; visualization of a joint effusion can reinforce the decision to do arthrocentesis despite surrounding erythema. NOTE: If infectious arthritis is strongly suspected, arthrocentesis should be done regardless of erythema or negative ultrasonographic results because joint infection must not be missed.
Severe bleeding diathesis, which may need to be corrected before arthrocentesis; routine therapeutic anticoagulation is not a contraindication, particularly if infection is suspected
Complications are uncommon and include
Damage to tendon, nerve, or blood vessels (traumatic tap)
Antiseptic solution (eg, chlorhexidine, povidone iodine, isopropyl alcohol), sterile gauze, sterile bandage, and sterile gloves
Local anesthetic (eg, 1% lidocaine, 25- to 30-gauge needle, 3- to 5-mL syringe)
For joint aspiration, a 25-mm (1-inch) 22-gauge needle and a 5-mL syringe
Appropriate containers for collection of fluid for laboratory tests (eg, cell count, crystals, cultures)
For intra-articular therapeutic injection, a syringe containing a corticosteroid (eg, triamcinolone acetonide 20 mg or methylprednisolone acetate 20 mg) and/or a long-acting anesthetic (eg, 0.25% bupivacaine), and a hemostat to help switch syringes
Enlist an assistant to provide flexion and traction to the toe.
Sterile technique is necessary to prevent microbial contamination of both the joint space and the aspirated synovial fluid.
A digital nerve block can be used for anesthesia.
The aspirating needle is inserted along the dorsal portion of the joint, just medial or lateral to the extensor hallucis longus tendon.
Arthrocentesis of the metatarsophalangeal joint
Synovial fluid is withdrawn from any of the metatarsophalangeal joints. The foot and toes are flat while the patient is supine and the knee is flexed. Needle entry occurs along the dorsal portion of the joint, just medial or lateral to the extensor hallucis/digitorum longus tendon.
Position the patient supine, with the knee flexed and the foot and toes flat on the stretcher.
Step-by-Step Description of Procedure
Have the patient dorsiflex the great toe. Then, in this position, palpate the dorsal aspect of the metatarsophalangeal (MTP) joint and the prominent dorsiflexed extensor tendon.
Rest the foot on an underpad. Prepare the area with a skin-cleansing agent, such as chlorhexidine or povidone iodine, then use an alcohol wipe to remove the agent.
Place a wheal of local anesthetic over the needle entry site using a 25- to 30-gauge needle.
Have an assistant manually plantarflex (about 20°) and apply axial traction to the toe to facilitate entry of the aspirating needle into the joint space.
Aspirate the joint using a 22-gauge needle. Enter the skin perpendicularly, at the level of the joint line, just medial or lateral to the extensor tendon. Direct the needle toward the center of the joint space. Gently pull back on the plunger as you advance. Synovial fluid will enter the syringe when the joint is entered.
If the needle hits bone, retract almost to skin surface and then redirect the needle at a different angle.
Drain all fluid from the joint.
If intra-articular drugs (eg, anesthetic, corticosteroid) are to be given, hold the hub of the needle motionless (using a hemostat if available) while removing the synovial fluid-containing syringe and replace it with the drug-containing syringe. If the needle has remained in place in the joint space, there will be no resistance to drug injection.
After injecting a corticosteroid, move the joint through full range of motion to distribute the drug throughout the joint.
Transfer synovial fluid to tubes and other transport media for synovial fluid analysis Synovial fluid examination Some musculoskeletal disorders affect primarily the joints, causing arthritis. Others affect primarily the bones (eg, fractures, Paget disease of bone, tumors), muscles or other extra-articular... read more . Inspect the fluid for blood and fat.
Apply an adhesive bandage or sterile dressing.
Ice, elevation, and oral nonsteroidal anti-inflammatory drugs may help relieve pain.
If an intra-articular anesthetic has been given, limited joint activity should be prescribed for 4 to 8 hours.
If an intra-articular corticosteroid has been given, a period of immobilization lasting about 24 to 48 hours may be needed.
If the patient has increased redness, pain, and swelling > 12 hours after the procedure, the joint should be examined for possible infection.
Warnings and Common Errors
Carefully ensure optimal positioning before joint puncture.
Allow adequate time for local anesthesia to take effect before proceeding.
To avoid damaging the synovium and articular cartilage, do not advance the needle against resistance and do not move the needle once it has begun draining synovial fluid.
If the needle tip must be relocated, first withdraw it almost to the skin surface and then redirect; do not try to change the angle of insertion while a needle is embedded in tissue.
Tips and Tricks
Note also that warmth, tenderness, and redness may overlie an acutely inflamed arthritic joint, mimicking extra-articular infection.
When trying to differentiate infectious arthritis from infection of the overlying structures (a contraindication to arthrocentesis Contraindications Arthrocentesis of the metatarsophalangeal (MTP) joint is the process of puncturing the MTP joint with a needle to withdraw synovial fluid. The procedure is described for the great toe but is... read more ), infectious arthritis is more likely with the following:
Circumferential joint pain
More pain with passive than active joint motion
When inspecting fluid, consider the following:
The hemarthrosis of a traumatic tap tends to be nonuniformly bloody and tends to clot.
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