Shoulder Arthrocentesis Technique

Steps in the performance of shoulder arthrocentesis are as follows:

• Obtain informed consent
• Palpate and mark the needle insertion site according to the approach chosen (see below)
• Sterilize the skin surrounding the insertion 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 injection is warranted, exchange the syringe for a corticosteroid-filled syringe and inject
• Remove the needle, and apply pressure and a bandage
• Divide the fluid among the specimen tubes

Needle placement accuracy rates appear to be significantly higher for the posterior approach to the glenohumeral joint than for the anterior approach. ^[8]

Ultrasonographic guidance

Prevention of unnecessary arthrocentesis is possible through confirmation of the effusion with ultrasonography (US). Procedural success is increased, and potential damage to important structures (vessels, tendons, ligaments, and cartilage) is minimized with visualization of the needle tip. An ultrasound probe sheath, chlorhexidine for site preparation, sterile gloves, sterile gel, and sterile drape are required.

With US guidance, the posterior approach accessing the posterior glenohumeral recess is preferred. After the transducer is aligned in the long axis with the infraspinatus, the needle is advanced from lateral to medial (or vice versa) until its tip is positioned near the surface of the humeral head hyaline cartilage. ^[9]

There are advantages to both in-plane and out-of-plane approaches. An in-plane approach does not allow neighboring structures to be identified, but it does provide the advantage of visualizing the entire length of the needle. An out-of-plane approach makes visualizing the needle tip difficult, but it allows improved visualization of the surrounding structures. The choice of approach is determined by the preferences of the provider and the depth of the joint. The curvilinear probe is ideal for the shoulder. ^[10]

Accuracy rates are also higher when imaging is used in conjunction with injection and aspiration. In a randomized trial comparing US-guided with blind steroid injection in patients with adhesive capsulitis of the shoulder, Raeissadat et al found that US-guided injections yielded improved accuracy, pain relief, range of motion, and function; however, these improvements were not statistically significant. ^[11]  In addition, the use of US guidance was associated with higher cost and was more time-consuming.

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). ^[12]

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 the scapulohumeral joint space (see the image below). ^[13]

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. ^[14]

Switching of syringe

If the practitioner wants to change the syringe, then the needle hub can be clasped with a hemostat. The hub should be clasped distally because the proximal portion can distort the opening. This technique is useful if corticosteroid injection follows aspiration or if an additional syringe is needed for complete aspiration.

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
• Vasovagal syncope