Shoulder Arthrocentesis 

Introduction

Shoulder arthrocentesis can be performed diagnostically for identification of the etiology of acute arthritis or therapeutically for drainage of an effusion. Using the same technique, the joint can be injected therapeutically with corticosteroids, anesthetics, or both.

The practitioner performing the procedure should be familiar with the anatomy of the glenohumeral joint and surrounding structures in order to avoid complications. The glenohumeral joint of the shoulder is formed by the humeral head and the glenoid fossa of the scapula. It is bounded by the acromion. The subdeltoid bursa lies under the deltoid muscle and covers the lateral and superior aspect of the proximal humerus. The neurovascular bundle lies medially in the axilla.

Three glenohumeral ligaments exist: (1) the superior glenohumeral ligament (SGHL), (2) the middle glenohumeral ligament (MGHL), and (3) the inferior glenohumeral ligament (IGHL). The SGHL has a variable origin and inserts on the humerus near the lesser tubercle; this ligament resists inferior translation of the humeral head in the adducted shoulder. The MGHL originates from the labrum and inserts on the humerus medial to the lesser tubercle; this ligament resists inferior translation in the adducted and externally rotated shoulder. The IGHL originates from the labrum and the adjacent glenoid neck, inserts on the anatomic neck of the humerus, and resists humeral head anterior and posterior translation. For more information about the relevant anatomy, see Shoulder Joint Anatomy.

Aspiration of the glenohumeral joint can be accomplished from an anterior or posterior approach. The posterior approach allows the patient to be blinded from the procedure, and it mimics the approach used in arthroscopy of the joint.

Indications

Diagnostically, shoulder arthrocentesis is used in patients with shoulder pain for injection of anesthetic (with or without corticosteroid), to determine whether the glenohumeral joint is the source of the patient's pain. By permitting joint aspiration, arthrocentesis aids in the diagnosis of the underlying pathologic process through synovial fluid analysis^{[1, 2]}

Therapeutically, shoulder arthrocentesis can be used to provide pain relief and functional improvement in glenohumeral osteoarthritis, rheumatoid arthritis, or adhesive capsulitis (this may be performed through drainage of an effusion, septic joint, or hemarthrosis or through instillation of medication.)

Contraindications

Bacteremia, cellulitis of overlying skin, and adjacent osteomyelitis are often considered absolute contraindications because of the potential risk of seeding the joint with bacteria. In these situations, the procedure should be performed only if the clinician strongly suspects septic arthritis as the cause of overlying inflammatory changes, and then only after consultation with an orthopedist.

Relative indications include glenohumeral joint infection, chronic infection distant to injection site, allergy to injectate, diabetes mellitus, or uncontrolled coagulopathy.

Anesthesia

Local anesthesia is recommended. For more information, see Local Anesthetic Agents, Infiltrative Administration.

After skin preparation and identification of the needle insertion site, use a 25-gauge needle to make a small skin wheal with local anesthetic into the subcutaneous tissue and then along the anticipated needle pathway.

Equipment

Equipment for shoulder arthrocentesis consists of the following:

• Alcohol sponges
• Skin cleansing agent (chlorhexidine [Hibiclens] or povidone-iodine [Betadine])
• Gauze
• Gloves (clean unsterile gloves sufficient if no contact made with skin or needle)
• Needles - 1.5-inch, 25-gauge for anesthetic injection and 18-22 gauge for aspiration; spinal needle may be needed for obese or muscular patients
• Syringes - 3-5 mL for anesthetic injection and 5-20 mL for aspiration
• Local anesthetic
• Specimen tubes
• Corticosteroid
• Bandage

Positioning

The patient should be seated in a comfortable position. For the anterior approach, rest the patient’s hand on his or her lap so the shoulder is internally rotated. For the posterior approach, place the patient’s hand on the contralateral shoulder.

Steps in the performance of shoulder arthrocentesis are as follows:

• Obtain informed consent
• Palpate and mark the injection site according to the approach chosen (see different approaches below)
• Sterilize the skin surrounding the injection site and allow it to dry
• Administer local anesthetic with a 25-gauge needle and a 3- or 5-mL syringe
• Insert an 18-gauge needle and aspirate on needle advancement into the joint space until synovial fluid is obtained
• If warranted, exchange syringe with corticosteroid-filled syringe and inject
• Remove needle and apply pressure and bandage
• Divide the fluid among the specimen tubes

Anterior approach

Palpate the coracoid process and the humeral head. As the arm is internally rotated, the joint space can be felt as a groove lateral to the coracoid process (see the image below).^[3]

Insert the needle medial to the head of the humerus and just below the tip of the coracoid process (see the image below).

Direct the needle slightly laterally and superiorly into scapulohumeral joint space (see image below).^[4]

Posterior approach

Insert the needle 1-2 cm inferior and medial to the posterior tip of the acromion. Direct the needle anteriorly and medially toward the coracoid.^[5]

Complications

Complications are uncommon and often insignificant but include the following:

• Hematoma and intravascular injection are possible because of the close proximity of the axillary vessels
• Iatrogenic infection is possible; the risk of inducing joint infection is low when sterile technique is used
• Injection of corticosteroids directly into a tendon or tendon insertion can sometimes result in tendon rupture
• Corticosteroids may cause a transient rise in blood glucose levels in patients with diabetes mellitus