Distal biceps tendon injuries refer to strains, partial and complete tears of the distal biceps tendon complex.
On this page:
Epidemiology
Distal biceps tendon injuries are far less common than injuries to the proximal biceps tendon with an incidence of approximately 1.2/100000 1,2. They typically occur in middle-aged men with a peak at around 50 years of age 1-3.
Risk factors
Conditions that account as predisposing factors for distal biceps injuries include the following 1,2:
male gender
smoking
anabolic streroid use
bodybuilding
Associations
Distal biceps injuries are associated with the following 4:
distal biceps tendinosis
Diagnosis
The diagnosis of a distal biceps tendon rupture can be established clinically, such as the Hook test, biceps crease interval or supination-pronation test 5. Tears can be confirmed and further evaluated with soft tissue imaging modalities such as ultrasound and MRI 1-5.
Clinical presentation
Typical presenting symptoms include severe pain in the antecubital fossa on eccentric loading accompanied by an audible snap or pop. Subsequent symptoms include pain and weakness in elbow flexion and/or forearm supination 1,2.
Clinical signs might inconsistently include bruising over the medial aspect of the elbow or an abnormal contour of the distal biceps 1.
The distal biceps tendon can be evaluated with the ‘Hook test’ by hooking the index finger into the distal biceps tendon from the lateral to the medial aspect. An abnormal test indicates a distal biceps tendon injury 1,2. Other clinical tests include the biceps crease interval and supination-pronation test.
Complications
If left untreated a distal biceps tendon injury can lead to atrophy and fatty degeneration of the biceps muscle with a reduction in elbow flexion and/or forearm supination strength 1.
Pathology
The high amount of fast-twitch (type II) muscle fibers and the biarticular configuration are considered risk factors for biceps injury. Most tears are complete and affect both tendons. Some tears are partial or isolated and affect either the more proximally located long head biceps tendon or the more distally inserting short head biceps tendon 3.
Etiology
Distal biceps tendon injuries usually occur in a weakened tendon during eccentric loading with the elbow in flexion and full supination 1.
Location
Distal biceps tendon injuries usually affect the distal zone or insertional tendon-bone interface and less commonly the musculotendinous junction proximally 3.
Classification
Distal biceps tendon injuries can be classified as acute (<4 weeks) or chronic (>4 weeks). They can be also subdivided into major and minor injuries based upon whether they require surgical management or not 6:
-
major injuries
complete tear or tendon rupture (with or without rupture of the lacertus fibrosus)
high-grade partial tear
-
minor injuries
low-grade partial tear
strain or tendinopathy
Radiographic features
Distal biceps tendon injuries are best evaluated with ultrasound and/or MRI and coverage of the whole distal biceps tendon from the musculotendinous junction to its distal insertion at the radial tuberosity is important 2.
Based on imaging features distal biceps tendon injuries can facilitate the classification of major and minor tendon injuries 2,6,7:
-
complete tear or tendon rupture: complete tendon disruption and loss of the distal attachment
intact lacertus fibrosus (direct visual confirmation on imaging or retraction gap <8 cm)
torn lacertus fibrosus (direct visual confirmation on imaging retraction gap >8 cm)
high-grade partial tear: discontinuity involving >50% of the biceps tendon
low-grade partial tear: discontinuity involving <50% of the biceps tendon
strain or tendinopathy: altered tendon signal or fiber pattern without evidence of discontinuity
Plain radiograph
The lateral radiograph of the elbow might show abnormal soft tissue shadowing with “Popeye deformity” 3.
Ultrasound
The distal biceps tendon can be examined from a medial longitudinal position with the forearm supinated and the elbow in a 20°-30° flexed position 7,8.
Partial and complete tears are characterized by partial or complete tendon discontinuity or detachment and/or peritendinous effusion with or without fiber retraction, whereas other alterations of the tendon without any evidence of fiber disruption (such as mere loss of the fibrillary pattern) indicate minor injuries as tendinopathy or elongation injury 5.
MRI
The distal biceps tendon can be evaluated in the FABS position in two longitudinal views 3,7,10,11 or with oblique coronal images besides the normal sagittal planes with the elbow resting close to the body 3.
Findings of distal biceps tendon injuries on MRI include the following 6:
tendon discontinuity
-
fluid or increased signal intensity of the following structures:
distal biceps tendon
distal biceps muscle
within the paratenon or in the peritendinous soft tissue
bone marrow edema of the radial tuberosity
Radiology report
The radiological report should include a description of the following 3:
distal biceps tendon injury (complete, partial, isolated tear)
the integrity of the lacertus fibrosus
tendon retraction with a gap
bicicpitoradial bursitis
Treatment and prognosis
Treatment options include non-operative, conservative or surgical management with distal biceps tendon repair or reconstruction.
Conservative, non-operative management is usually associated with significant declines in supination and elbow flexion strength and therefore reserved for patients with either strain and/or partial tears, significant peri-operative risks or low functional demands 1.
Distal biceps repair is usually done in acute distal biceps tendon injuries involving >50% of the distal biceps tendon where anatomical repair is feasible, whereas distal biceps tendon reconstruction is used to restore elbow flexion and/or supination power in the situation of a chronic distal biceps tendon rupture and if repair is no longer feasible 1,12,13.
Differential diagnosis
Conditions that might mimic the imaging appearance of a distal biceps tendon injury include 3,4:
degenerative enthesopathy/enthesitis
brachialis muscle injury (rare)