Shoulder arthrocentesis is a necessary and practical skill in the hands of emergency physicians, surgeons, medical specialists and primary care providers alike. It is a useful procedure for both diagnostic and therapeutic indications and has very few contraindications. It is part of the initial evaluation for the exclusion of infection in monoarticular arthritis of unclear etiology. It can be used in rheumatologic and traumatic causes differentiating between gout and pseudogout and hemarthroses. Therapeutically, it can be used to drain symptomatic effusions or hemarthroses as well as to inject steroid or local anesthetic both for pain relief and to facilitate shoulder reduction in an awake patient, reducing the need for procedural sedation and IV pain medication.
To prevent complications, the clinician should be familiar with the shoulder anatomy.
The humeral head and the glenoid fossa of the scapula form the glenohumeral joint of the shoulder. The entire joint is associated with the acromion. Just under the deltoid muscle lies the subdeltoid bursa and may extend to the superior and lateral aspect of the proximal humerus. Medial to the axilla lies the neurovascular bundle.
The only absolute contraindication to the procedure is cellulitis overlying the entry point; however, known bacteremia is a relative risk as this procedure in the bacteremic patient could theoretically seed the joint space. High suspicion for bacterial joint infection should prompt synovial fluid analysis even in the bacteremic patient as the risks of improper or incomplete treatment of a septic joint far outweigh the theoretical risk of seeding the joint with bacteria. Another relative contraindication is a bleeding disorder or anticoagulant therapy as this could introduce hemarthroses; however, this risk is low compared to risks associated with bacterial joint infection. Prosthetic joints are considered to be a relative contraindication by some outside of a sterile, surgical environment. However, emergent arthrocentesis may be required if a sterile OR environment is not available.
Aseptic Skin Preparation
Specimen collection tubes
As with any medical procedure, the keys to success often lie in thorough preparation. Since there are no hyperacute indications for arthrocentesis of the shoulder, adequate preparation time should always be taken to maximize success and to minimize risk.
Technique: Anterior Approach
After prepping, sterilizing and draping the skin, the most important step in the shoulder arthrocentesis technique is the proper identification of landmarks which will determine the point of entry into the joint. These landmarks include the humeral head, distal clavicle, and coracoid process. The point of entry is medial to humeral head and inferior/lateral to the coracoid process. Insert needle perpendicular to the skin and into the joint space as depicted in the figure. If you chose to identify your landmarks prior to to the sterilization process, using a skin impression or marking pen at the site of insertion can maintain an accurate position during the prepping and draping of the skin.
While drawing back on the plunger to check for intra-articular blood or synovial fluid. Once the syringe is filled, a hemostat can be placed on the hub of the needle to facilitate removal of a syringe filled with synovial fluid to be sent for analysis and placement of an additional syringe (if needed) to draw of any additional fluid. This same synringe exchange technique can be used to attach a syringe filled with local anesthetic and or injectable steroid as indicated. The skin is then cleaned, and a bandage is placed.
The most important risk to discuss with the patient is an iatrogenic infection. While this complication is rare (approximately 1/10000), it remains a possibility.
Joint Fluid Analysis