Anatomical and imaging features
The distal tendon of the biceps brachii (tendo musculi bicipitis brachii) attaches to the tuberosity of the proximal radius. An important anatomical feature is that it lacks a true synovial sheath—instead, the tendon is surrounded by specialized connective tissue, the paratenon (paratenon). The bicipitoradial bursa (bicipitoradial bursa) is located in close proximity to the insertion site.
On plain radiographs in the area of the enthesis (attachment site), new bone formation can sometimes be detected. It is worth noting that calcific tendinopathy (calcific tendinopathy) in this region is significantly less common compared to rotator cuff lesions of the shoulder.
Ultrasound examination (US)
Ultrasound is an effective method for confirming the diagnosis and accurately localizing the injury.
- Normally, during longitudinal scanning, the tendon has a homogeneous echostructure and constant size all the way to its insertion site on the radius.
- In early stages (tendinopathy), the structure changes. In patients with elbow pain, the tendon appears significantly thickened, and its echogenicity decreases. In this phase, effusion in the bicipitoradial bursa is frequently visualized. Sonograms also clearly demonstrate the close anatomical proximity of the pathologically altered tendon to the brachial vessels.
- In a complete tear, retraction (shortening and proximal migration) of the tendon occurs. On ultrasound, the torn end is highlighted by a specific acoustic shadow (caused by edge refraction artifact). Hypo- or anechoic fluid accumulates in the distal part of the tendon sheath. The biceps (Biceps) and brachialis (Brachialis) muscles are usually well-differentiated on the images.
Magnetic resonance imaging (MRI)
MRI is considered the gold standard for assessing the degree of retraction and planning surgical intervention.
- On T2-weighted fat-suppressed images (FS T2) in the sagittal plane, a complete tear is identified as a zone of hyperintense signal. This signal is caused by extensive hemorrhage surrounding the retracted tendon end, the contours of which become blurred.
- For the most accurate visualization of the defect, the specialized FABS position is used. On such tomograms, the torn end and the completely empty tendon sheath filled with fluid, extending down to the radial tuberosity, can be clearly traced.
Briefly: answers to topical questions
What does the acronym for the FABS positioning in elbow MRI stand for?
The FABS positioning acronym in elbow MRI stands for Flexion in the elbow, Abduction of the shoulder, and Supination of the forearm. This special projection is used to visualize the torn tendon end and the empty, fluid-filled tendon sheath extending down to its insertion site on the radial tuberosity.
Which nerves and vessels are topographically related to the distal biceps tendon in the cubital fossa?
In the cubital fossa, the distal biceps brachii tendon is topographically related primarily to the brachial vessels.
- The brachial artery (a. brachialis) is projected at the medial margin of the m. biceps brachii; the artery lies closer to the biceps tendon.
- The median nerve (n. medianus) is projected 0.5–1.0 cm medial to the brachial artery and is located closer to the medial epicondyle.
Sonograms of the distal biceps tendon demonstrate its close anatomical relationship with the brachial vessels.
To assess a complete tear on MRI, remember the FABS positioning: Flexion, Abduction, Supination. It ideally demonstrates the empty tendon sheath and the torn end of the biceps.
Class and exam questions
What happens to the biceps tendon in a complete tear?
Its retraction (shortening and proximal migration) occurs. This is clearly visible on ultrasound and MRI as the absence of the tendon in its typical location, along with fluid accumulation or hemorrhage.
Why is the FABS projection needed on MRI?
It helps clearly visualize the torn end of the distal tendon and trace the empty, fluid-filled sheath all the way down to the radius.
What does biceps tendinopathy look like on ultrasound?
The tendon becomes thickened and loses its normal echogenicity (becomes hypoechoic). Effusion in the bicipitoradial bursa is also frequently identified.
What else to study on this topic
- MRI and ultrasound features of lateral epicondylitis ("tennis elbow")
- Post-traumatic osteolysis of the lateral end of the clavicle
- Osteochondritis dissecans of the humeral capitellum
- Assessment of osteochondral defect stability on MRI
- Diagnosis of loose intra-articular bodies in elbow osteoarthritis
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Imaging diagnostics of biceps brachii tendon injuries" and 2,199 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other topics in the "Musculoskeletal System" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.