Mohini Rawat, DPT, MS, ECS, OCS, RMSK
Contents
- Patient position: Sitting with elbow resting on the table with full supination and extension
- Probe/transducer position: The probe is placed transversely on the anterior aspect of the elbow to visualize the joint in the short axis (SX) view. The probe is then rotated 90 degrees to visualize the anteromedial and anterolateral aspect of the joint in the long axis (LX) view (Figures 3-1 through 3-4).
Figure 3-1. SX view of the anterior elbow. (A) Probe placement. (B) Ultrasound image of the anterior elbow in the SX view. A hyperechoic bony interface is lined by an anechoic cartilage interface. The distal biceps tendon (white arrow) is hyperechoic and the most superficial tendon. (C) Relevant anatomy and probe placement.
Figure 3-2. Expanded SX view of the anterior elbow showing soft tissue structures. The radial nerve (yellow arrow) is between the brachialis and brachioradialis muscles. The median nerve (white arrow) is between the brachialis and pronator teres muscles.
Figure 3-3. Anterolateral LX view of the elbow. (A) Probe placement. (B) Ultrasound image of the anterolateral elbow in the LX view, showing the radial fossa (white arrow), joint (white triangle), and radial head and neck. (C) Relevant anatomy and probe placement.
Figure 3-4. Anteromedial LX view of the elbow. (A) Probe placement. (B) Ultrasound image of the anteromedial elbow in the LX view, showing the coronoid fossa (white arrow), joint (white triangle), coronoid process (CP), and trochlea of the humerus. (C) Relevant anatomy and probe placement.
- Relevant anatomy: The distal humerus is seen as a hyperechoic bony interface lined by anechoic cartilage above the bony surface. The convex surface is the capitellum, and the concave surface is the trochlea, which is divided into lateral and medial facets.1 Overlying the joint surface is the brachialis muscle belly. On the radial side, the brachioradialis muscle can be seen. Between the brachialis and brachioradialis is the radial nerve. On the ulnar side, the pronator teres muscle is seen. Between the brachialis and pronator teres, the median nerve is seen next to the brachial artery.
- Points to remember: Cartilage is best visualized with full extension of the elbow. Adding flexion may limit visualization of the cartilage-lined surface of the distal humerus.
- Relevant anatomy: The distal humerus is seen as a hyperechoic bony interface lined by anechoic cartilage above the bony surface. The convex surface is the capitellum, and the concave surface is the trochlea, which is divided into lateral and medial facets.1 Overlying the joint surface is the brachialis muscle belly. On the radial side, the brachioradialis muscle can be seen. Between the brachialis and brachioradialis is the radial nerve. On the ulnar side, the pronator teres muscle is seen. Between the brachialis and pronator teres, the median nerve is seen next to the brachial artery.
Relevant anatomy of the distal biceps tendon (DBT) is shown in Figure 3-5.
Figure 3-5. Relevant anatomy of the DBT, which twists from predominantly the frontal plane to the sagittal plane before inserting on the radial tuberosity. As the DBT crosses the elbow joint, a thin fibrous structure, the lacertus fibrosus or bicipital aponeurosis (green), fans out in the ulnar direction and merges with the superficial fascia to span the flexor muscle compartment of the forearm.
- Patient position: Sitting with full supination and slight elbow flexion
- Probe/transducer position:
a. SX view: The probe is placed transversely on the anterior aspect of the elbow to visualize the DBT (Figure 3-6).
Figure 3-6. SX view of the DBT, anterior approach. (A) Probe placement. (B) SX view of the DBT (white arrow).
b. LX view:
i. Anterior approach: The probe is rotated 90 degrees from the SX view to visualize the DBT in the LX view, and the tendon is followed distally to its insertion site at the radial tuberosity. In the distal part, passive supination of the forearm and increased pressure on the distal part of the probe are needed to visualize the distal insertional fibers of the DBT (Figure 3-7).1,2
Figure 3-7. LX view of the DBT, anterior approach. (A) Probe placement. (B) LX view of the DBT (white arrows). (RH = radial head.)
ii. Lateral approach: The probe is placed on the lateral aspect of the elbow with the elbow flexed to 90 degrees and the forearm supinated to visualize the DBT in the LX view through the acoustic window of the muscle mass of the forearm extensors, brachioradialis, and supinator muscle (Figure 3-8).1,3
Figure 3-8. LX view of the DBT, lateral approach. (A) Probe placement: probe (red rectangle), DBT (blue arrow), radius (yellow rectangle), ulna (black rectangle). (B) With the elbow flexed to 90 degrees and the forearm supinated, the DBT (white arrows) is visualized in the LX view through the acoustic window of the muscle mass of the forearm extensors (E), brachioradialis, and supinator muscle (S).
iii. Medial approach: With the elbow flexed to 90 degrees and the forearm supinated, the probe is placed in the LX on the medial aspect to visualize the DBT through the acoustic window of the flexor-pronator mass. The brachial artery is medial to the DBT and helps enhance echogenicity of the DBT with this approach (Figure 3-9).1,4
Figure 3-9. LX view of the DBT, medial approach. (A) Probe placement. (B) LX view of the DBT (white arrows) showing the brachial artery (white triangle). With the elbow flexed to 90 degrees and the forearm supinated, the probe is placed in the LX on the medial aspect to visualize the DBT through the acoustic window of the flexor-pronator mass. The brachial artery is medial to the DBT.
iv. Posterior approach: This is a limited view of the distal portion of the DBT fibers. The elbow is maximally flexed and resting on the table with the forearm in full pronation and the wrist flexed. The probe is placed transversely between the radius and ulna at the level of the radial tuberosity, about 4 cm distal to the olecranon process. A dynamic maneuver of supination and pronation will show the DBT with pronation and cause it to disappear upon supination (Figure 3-10).1
Figure 3-10. LX view of the DBT, posterior approach. (A) Probe placement. (B) The DBT (white arrow) between the radius and ulna. The elbow is maximally flexed and resting on the table with the forearm in full pronation and the wrist flexed. The probe is placed transversely between the radius and ulna at the level of the radial tuberosity, about 4 cm distal to the olecranon process. (C) Relevant anatomy and probe placement.
- Relevant anatomy: The DBT twists from predominantly the frontal plane to the sagittal plane before inserting on the radial tuberosity. As the DBT crosses the elbow joint, a thin, fibrous structure called lacertus fibrosus, or bicipital aponeurosis, fans out in the ulnar direction and merges with the superficial fascia to span the flexor muscle compartment of the forearm.5 The footprint of the DBT on the radial tuberosity is divided into 2 parts: a larger proximal footprint for the long head of the biceps fibers and a small, thin distal footprint for the short head of the biceps fibers.5 The DBT is surrounded by bicipitoradial bursa, which in normal states is not depicted on ultrasound.
- Points to remember: Because of the 90-degree twist in the DBT fibers from the frontal plane to the sagittal plane and the sudden change in the course of the tendon from being the most superficial tendon at the level of the elbow joint to the most posterior as it inserts on the medial aspect of radius, scanning the tendon in the LX view can be challenging. Knowledge of fiber orientation and course of the tendon is helpful in proper visualization of the tendon. Full supination and increased pressure on the distal end of the probe to make the probe parallel to the tendon is important to counter the refraction artifact due to the oblique direction of the fibers.
- Relevant anatomy: The DBT twists from predominantly the frontal plane to the sagittal plane before inserting on the radial tuberosity. As the DBT crosses the elbow joint, a thin, fibrous structure called lacertus fibrosus, or bicipital aponeurosis, fans out in the ulnar direction and merges with the superficial fascia to span the flexor muscle compartment of the forearm.5 The footprint of the DBT on the radial tuberosity is divided into 2 parts: a larger proximal footprint for the long head of the biceps fibers and a small, thin distal footprint for the short head of the biceps fibers.5 The DBT is surrounded by bicipitoradial bursa, which in normal states is not depicted on ultrasound.
- Patient position: Sitting with elbow extension and resting on the table
- Probe/transducer position: The probe is placed transversely on the anterior aspect of the elbow to visualize the brachialis in the SX view, and then the probe is moved distally in the SX view to visualize the distal portion of the brachialis. The probe is rotated 90 degrees to scan the brachialis muscle tendon complex in the LX view as it attaches on the coronoid process of the ulna (Figures 3-11 and 3-12).
Figure 3-11. SX view of the brachialis. (A) Probe placement. (B) SX view of the brachialis muscle (white arrow) at the proximal level. (C) SX view of the brachialis muscle tendon (white arrow) at the distal muscle tendon level.
Figure 3-12. LX view of the brachialis. (A) Probe placement. (B) LX view showing the superficial head (SH) and deep head (DH) of the brachialis attaching to the coronoid process.
- Relevant anatomy: The brachialis is divided into 2 parts: The larger superficial head originates from the anterolateral aspect of the middle third of the humerus and lateral intermuscular septum, and the deep head originates from the distal third of the anterior aspect of the humerus and the medial intermuscular septum. The brachialis continues distally and inserts on the coronoid process of the ulna. The superficial head attaches more distally than the deep head.6
- Points to remember: The tendon of the distal brachialis is thinner than the DBT. Variations of the distal insertion of the brachialis tendon on the coronoid process of the ulna include purely muscular, tendinous, or mixed.1
- Relevant anatomy: The brachialis is divided into 2 parts: The larger superficial head originates from the anterolateral aspect of the middle third of the humerus and lateral intermuscular septum, and the deep head originates from the distal third of the anterior aspect of the humerus and the medial intermuscular septum. The brachialis continues distally and inserts on the coronoid process of the ulna. The superficial head attaches more distally than the deep head.6
Relevant anatomy of the region is shown in Figure 3-13.
Figure 3-13. Relevant anatomy of the pronator teres, which has 2 heads: the humeral head and ulnar head. The 2 heads fuse to form a muscle belly, which inserts through a short tendon on the lateral aspect of the middle third of the radius. The median nerve runs between the ulnar and humeral heads of the pronator teres. The ulnar artery runs deep to the ulnar head of the pronator teres.
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