Quick Guide to Diagnostic Ultrasound of the Elbow
Moving along with the ultrasound series, the elbow will now be covered. The elbow is a synovial hinge joint with three articulations. These include the capitellum and radial head, the trochlea and the ulna and the proximal ulna and radius. Each joint recess has an extrasynovial fat pad that can be displaced with injury, with a common radiographic sign observed with this being called the “sail sign.” The ulnar collateral and radial collateral ligaments stabilize the medial and lateral elbow, with these ligaments becoming common sources of elbow pain in throwing athletes.
Image 1. Anterior elbow/ antecubital fossa. A = brachial artery, PT = pronator teres, B = brachialis, BT = biceps brachii tendon, BR = bracioradialis, H = humerus, curved arrow = medial nerve, open arrow = musculocutaneus nerve (adopted from )
The biceps brachii acts to flex and supinate the elbow and evaluating the distal biceps tendon can be technically challenging due to its steep oblique course and 90° rotation. It will occasionally help visualization if the elbow is supinated as far as possible [Figure 2]. This may bring the tendon insertion at the radial tuberosity into view. It is best seen utilizing the transverse plane . The transducer should be positioned slightly inferolaterally with attention to maintaining the probe parallel to the tendon as it courses obliquely away from the probe to its insertion [Figure 3]. Application of more pressure on the distal half of the transducer (“heel-toe maneuver”) aids in maintaining a perpendicular relationship between the ultrasound beam and the distal biceps tendon. Varying degrees of flexion and extension can also aid in visualization.
Image 2. Positioning for examination of distal biceps tendon insertion (adopted from )
Image 3. Distal biceps tendon with asterisks and arrows. DB = distal biceps, BR = brachialis, PT = pronator teres, R = radius (adopted from )
Image 4. The cobra maneuver can also be used if there is difficulty with visualization of the distal biceps tendon (adopted from )
Image 5. Radiocapitellar joint. C = capitellum, RH = radial head, BR = brachioradialis (adopted from )
Image 6. Coronoid fossa. B = brachialis (adopted from )
Image 7. Positioning for the medial elbow evaluation (adopted from )
Image 8. Anterior band of the ulnar collateral ligament (adopted from )
Image 9. One technique to perform valgus stress on the elbow and the ultrasound can be used to assess for joint space opening and compared to the opposite side. Red depicts location of the transducer (adopted from ).
Image 10. The cubital tunnel (adopted from )
Image 11. Positioning for testing of ulnar nerve instability. The nerve would be evaluated with the elbow in flexion and extension (adopted from )
Image 12. The ulnar nerve (arrowhead) and the triceps (T) posterior to the medial epicondyle (E) (adopted from )
Image 13. The common extensor tendon (dark arrows), radial collateral ligament (arrowheads) and the annular ligament (bracket) (adopted from )
Image 14. LUCL (adopted from )
Image 15. (A) the superficial and deep branches of the radial nerve (arrows) deep to the brachioradialis (B). Proximal imaging (B) shows the radial nerve branches have joined to form radial nerve (arrowheads adjacent to the posterior humerus (H). Distal imaging shows deep branch of the radial nerve (arrow) in short axis (C) and long axis (arrowheads) (D) within the two heads of the supinator muscle (S). (adopted from )
Figure 16. Posterior elbow evaluation “Crab” position (adopted from ).
Figure 17. Normal olecranon fossa and distal triceps tendon and muscle. Logitudinal US image shows the normal hypoechoid triceps muscle belly (TM) and the more hyperechoic fibrillar distal triceps tendon (arrowheads) as it approaches its insertion approximately 1 cm distal to the apex of the olecranon (O). The posterior fat pad (*) is seen within the olecranon fossa, which is bounded by the echogenic contour of the humerus (H). (adopted from )
In conclusion, ultrasonography is an excellent diagnostic imaging modality for a wide range of abnormalities affecting the elbow joint and surrounding structures. The sonographer should be familiar with proper US techniques for the elbow and it is important to have sufficient ultrasound gel with many of the structures being evaluated. Ultrasound can be extremely useful for point of care due to the added dynamic component available with conditions such as UCL instability or ulnar nerve instability. These are sometimes the very important factors for orthopedic surgeons while making decisions of operative versus nonoperative management.