Emergency physicians must consider septic arthritis when evaluating patients presenting with a painful and swollen elbow. The clinical exam, even in combination with serum laboratory markers, is not adequately sensitive to rule out a septic joint making arthrocentesis with synovial fluid analysis mandatory once the presence of a new effusion has been verified.1
Explore This IssueACEP News: Vol 32 – No 09 – September 2013
Pic.1A: A linear high frequency ultrasound probe is needed to image the elbow. 1B: Gather supplies required for an ultrasound-guided elbow arthrocentesis.
Overlying tissue edema and obesity often limit the ability of clinicians to assess accurately the presence of an effusion and palpate classic landmarks needed for “blind” joint aspiration.2
Sonography has proven to be superior to both the physical exam and plain film radiography in detecting the presence of joint effusions, while also confirming alternative diagnoses such as cellulitis, abscesses, and soft tissue hematomas.3,4
Pic. 2: Have the patient abduct the shoulder, flex the elbow to 90 degrees and pronate the forearm. Placing a pillow or towel under the forearm will allow for easier visualization of the joint space.
The absence of effusion in the capsule surrounding the elbow joint on ultrasound (in conjunction with the clinical exam) may prevent an unnecessary invasive joint aspiration.4
Along with delineating anatomical landmarks and detecting the presence of joint effusion, point-of-care ultrasound can be used to guide needle aspiration during arthrocentesis.
Ultrasound guidance has been shown to improve success rates compared to classic landmark techniques, and having a simple protocol can be invaluable for the clinician performing elbow arthrocentesis.5
Pic. 3: Slide the linear transducer proximally until the radio-capitellar joint is imaged.
Elbow Effusion Identification by Bedside Ultrasound
We recommend using the linear transducer (10-5MHz) for both the identification of the effusion and needle guidance for the arthrocentesis (Pic 1A). The elbow can be assessed for the presence of effusion from both the lateral and posterior approaches, with the lateral approach preferred for arthrocentesis.
We always recommend first examining the non-affected elbow with ultrasound for clinical comparison of the joint capsule. For the lateral approach to the elbow joint capsule, the goal is to find the soft triangular junction between the lateral epicondyle of the humerus, the radial head, and the olecranon.
Pic. 4: Look for anechoic (black) space between and above the radio-capitellar joint. The displacement of the joint capsule denotes a joint effusion.
The patient should be placed in a sitting upright position with the affected arm abducted, resting to the patient’s side, pronated, and flexed to 90 degrees (Pic 2). Place the transducer along the proximal forearm in a longitudinal fashion, parallel to the shaft of the radius, and with the probe marker towards the patient’s head.