Shoulder Arthrocentesis Technique

Shoulder arthrocentesis (shoulder aspiration) is a necessary and practical skill in the hands of emergency physicians, surgeons, medical specialists, and primary care providers. A clinically useful procedure for both diagnostic and therapeutic indications, shoulder joint aspiration as a diagnostic procedure limited relative contraindications. [1]

Shoulder aspiration/injection techniques are commonly utilized in various treatment and management modalities.  Aspiration techniques are often used in clinical settings that require synovial fluid analysis to aid in diagnosing inflammatory or septic arthritis.  Also, shoulder aspiration techniques can be used in rheumatologic and traumatic causes, such as when attempting to clinically differentiate between suspected infection cases versus gout, pseudogout, and/or traumatic hemarthroses.[2] 

Therapeutically, the technique is utilized to aspirate (or "drain") shoulder joint effusions in addition to coupling the aspiration with the injection of a local steroid and/or anesthetic for pain relief and to facilitate shoulder reduction in an awake patient.  The latter can be beneficial for the patient and help mitigate other risks associated with procedural sedation and IV pain medication use.  Glenohumeral intra-articular injections can also be utilized to treat pain/symptomatic management of shoulder degenerative joint diseases.

In the setting of clinical suspicion for periprosthetic joint infections (PJI), in this case, following either a standard total shoulder arthroplasty (TSA), reverse total shoulder arthroplasty (rTSA), or a shoulder hemiarthroplasty, aspirations sent for extended culture incubation time periods (i.e. 2 to 3 weeks) can be clinically useful to aid clinicians in the appropriate management of these conditions. [3][4]

The clinician should be familiar with the glenohumeral (GH) joint and shoulder girdle anatomy to prevent complications.

Osseous Elements

The shoulder girdle consists of the scapula and clavicle, which articulate with the chest wall, and the proximal humerus, which articulates with the scapula (the glenoid).  The humeral head and the glenoid vault of the scapula form the osseous components of the shoulder's glenohumeral joint. 

Surrounding osseous components that can potentially be implicated in associated/related pathologic conditions include the other portions of the scapula, including the body, spine, and most laterally, the acromion.  The latter can be implicated in conditions relating to shoulder external impingement and rotator cuff syndrome [5][6][7].

Soft Tissue Components

Bursa

Shoulder injections technique can include extra-articular and periarticular injections to various anatomic locations.  The most common location is the subacromial space of the shoulder.  The subacromial space exists as a bursal cavity lying between the rotator cuff (inferiorly) and the acromion process (superiorly).  Also, the most lateral component of this cavity becomes contiguous with the subdeltoid bursa/space.

Neurovascular elements

Critical knowledge of the surrounding neurovascular structures is of the utmost importance when planning for a shoulder joint aspiration/injection.  

The shoulder joint derives its nerve supply from three branches of the brachial plexus (C5/C6):

• Suprascapular nerve
• Axillary nerve
• Lateral pectoral nerve

The axillary nerve and the posterior circumflex humeral artery pass through the quadrilateral or quadrangular space, which lies inferior and posterior to the GH joint.  The quadrangular space includes the following borders/boundaries:

• Superior: Teres minor
• Inferior: Teres major
• Medial: Long head of the triceps
• Lateral: Proximal humerus/humeral shaft 

Diagnostic Indications[8][9][10]

• Diagnosis of infectious/septic arthritis
• Diagnosis of inflammatory arthritides/crystalline arthropathy 
• Diagnosis of traumatic injury (bony or ligamentous)
• Rule out traumatic arthrotomy (in the setting of penetrating trauma, lacerations, gunshot wounds (GSW))

Therapeutic Indications

• Steroid/cortisone injections
• Local anesthetic injections
• Relief of symptomatic, distended effusions
• Relief of hemarthroses to prevent synovial hypertrophy and fibrosis

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.

Materials

Aseptic Skin Preparation

• Sterile gloves
• Iodine solution or chlorhexidine skin prep
• Sterile gauze pads
• Sterile, fenestrated drape

Needles

• 25G or 27 G for anesthetic and steroid injection
• 20-22 G for aspiration (depending on viscosity fluid to be aspirated)

Luer-Lok Syringes

• 3-5 mL for injection
• 5-20 mL for aspiration

Medications

• Anesthetic: Lidocaine 1% or Bupivacaine 0.5% (shoulder will accommodate 3-5 mL)
• Steroid: Methylprednisolone acetate (Depo Medrol) 40 mg or Triamcinolone acetonide (Kenalog) 40 mg

Testing Equipment

Specimen collection tubes

• Hematology tube for cell count and differential
• Sterile tube for Gram stain, culture, and smear
• Heparinized tube for crystal analysis