Arthrocentesis of the shoulder is the process of puncturing the glenohumeral joint with a needle to withdraw synovial fluid. The anterior approach, which is described here, is most common and can be technically difficult. A posterior approach is also possible.
- 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
- Prosthetic joint, which is susceptible to iatrogenic infection; prosthetic joint arthrocentesis should be done by an orthopedic surgeon
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
- Nonsterile pads
- Local anesthetic (eg, 1% lidocaine, 25-gauge needle, 3- to 5-mL syringe)
- For joint aspiration, a 51-mm (2-inch) 20-gauge needle and 20-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 40 mg or methylprednisolone acetate 40 mg) and/or a long-acting anesthetic (eg, 0.25% bupivacaine), and a hemostat to help switch syringes
- Sterile technique is necessary to prevent microbial contamination of both the joint space and the aspirated synovial fluid.
- Needle insertion is inferior and lateral to the coracoid process and medial to the humeral head.
Arthrocentesis of the shoulder
The glenohumeral joint is punctured while the patient sits with the arm at the side and the hand on the lap. The needle is inserted anteriorly, slightly inferior and lateral to the coracoid process, aiming posteriorly toward the glenoid fossa, and medial to the humeral head. A posterior approach is also possible.
- Position the patient sitting upright on the stretcher, with the affected arm adducted and the hand in or near the lap (ie, arm internally rotated).
Step-by-Step Description of Procedure
- Palpate the glenohumeral joint to identify the clavicle, the coracoid process, and the humeral head. If desired, mark the needle entry site with a skin-marking pen.
- 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 entry site using a 25-gauge needle. Then inject more anesthetic along the anticipated trajectory of the arthrocentesis needle, but do not enter the joint space.
- Palpate the landmarks, including the coracoid and the humeral head.
- Aspirate the joint using a 20-gauge needle. Enter the skin perpendicularly, inferiorly, and lateral to the coracoid process and medial to the humeral head. Direct the needle posteriorly, toward the glenoid rim, and 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 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. 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/or 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
Consider doing ultrasonography if there is no obvious large effusion.
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), infectious arthritis is more likely with the following:
- Joint effusion
- 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.
- Fat within a hemarthrosis (lipohemarthrosis) is caused by an occult fracture.
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