Dr. Bouffard is a Senior Staff Radiologist in Muskuloskeletal Radiology, in the Department of Diagnostic Radiology, Henry Ford Hospital, Detroit, MI. Dr. Lee is a Musculoskeletal Radiologist with Medical Imaging of Denton, Denton, TX.

Rupture of the distal biceps tendon (DBT) is a rare occurrence and is usually associated when a sudden force is applied on a flexed elbow. Often challenging to evaluate clinically, urgent diagnosis is necessary for prompt repair of the distal biceps to preserve function and flexibility at the elbow. Although magnetic resonance imaging (MRI) has been the mainstay of diagnosis in this arena, musculoskeletal ultrasound (MSUS) is increasingly being recognized as an efficacious modality to diagnose not only the presence of a tear in the DBT, but also its extent and the degree of retraction. The authors present a case report of a torn DBT as an example of the application of MSUS.

Case Summary

A 50-year-old man presented with a bruised distal biceps area following a lifting injury. He had felt a "pop" with a subsequent swelling, bruising, and pain over the distal left arm and elbow. Physical examination revealed an asymmetrically enlarged and tender distal left arm (the "Popeye" sign) with diminished strength in flexion and supination at the elbow.

Imaging Findings

The patient was evaluated with an Antares ecograph (Siemens-Acuson, Mountain View, CA) using a 5- to 13-MHz linear array transducer. The images were reviewed on a generic picture archiving and communication system (PACS). Only soft copy images were used for interpretation, annotation, and illustration.

The MSUS images were obtained following the protocol established in our institutions for routine exploration of the elbow. Long-axis and short-axis views of the DBT were obtained with the elbow in extension and, simultaneously, the wrist and hand in hypersupination. The bony acoustic landmarks of the radial head, neck, tuberosity, distal humeral condyles, and brachial artery were used for orientations in long- and short-axis evaluations. Additional images in nonorthogonal planes and color Doppler images were obtained to optimize the separation of the brachial artery from the intimately adjacent DBT. Short-axis images at the level of the radial tuberosity with the elbow in full-flexion and wrist in flexion-pronation were also obtained for visualization of the DBT insertion onto the radial tuberosity.

Routine MSUS images of the symptomatic elbow of the patient demonstrated a large hypoechoic collection of abnormal fluid over the antecubital fossa, representing a hematoma (Figure 1). The DBT was completely torn, retracted, and coiled over the brachialis muscle, and surrounded by capacious hematoma (Figures 2 and 3). There was an interruption of the fibrillar pattern of the tendon insertion into the radial tuberosity (Figure 4). A small residual stump or flap of the tendon at the radial tuberosity was noted. There was no bony avulsion fragment from the radial tuberosity. The elbow joint had no effusion.

The ultrasound images were diagnostic of a completely ruptured DBT, corroborating the clinical examination. The orthopedic surgeons recommended surgery to repair the tendon, but the patient has not yet decided to have it.

Discussion

Rupture of the DBT is an uncommon musculoskeletal injury, representing <5% of all biceps tendon injuries of the arm. It is usually seen in men 40 to 60 years of age who are manual laborers, construction workers, athletes, or weight lifters. The injury most frequently occurs during heavy lifting with the elbow flexed 90° or when the biceps muscle contracts suddenly and forcefully against unexpected resistance. Occasionally, spontaneous ruptures can occur without a specific history of trauma. ^1,2 The dominant arm is more commonly affected. ³ Early diagnosis of this injury, differentiation of partial from complete rupture, and measurement of the degree of retraction are important in planning patient management. ^4,5

The clinical diagnosis of DBT injury may be challenging in partial tear, nonretracted complete tear, or brachialis tendon injury. Swelling or edema obscures the tendon defect, and palpable thickened lacertus fibrosus may also lead to a misdiagnosis of an intact tendon. Differentiation of partial versus complete rupture is important since complete ruptures generally require surgical repair, while partial ruptures are traditionally treated conservatively. Two weeks following the injury, scarring and retraction of the tendon make the surgery more difficult, so early diagnosis is important. ^4,5

Although magnetic resonance imaging (MRI) has been the mainstay of diagnosis in this arena, ^6-9 musculoskeletal ultrasound (MSUS) is increasingly being recognized as an efficacious modality to diagnose not only the presence of a tear in the DBT, but also its extent and the degree of retraction. ^10-13 The authors report this case of a torn DBT as an example of the application of MSUS.

With ultrasound, the direct signs of complete rupture are nonvisualization of the distal biceps tendon with fluid collection or hematoma (Figures 1 to 3) within the tendon sheath or gap, along with truncated proximal (Figure 2) and distal stumps of the retracted tendon. Granulation tissue or hematoma within the tendon sheath or irregular synovial thickening of the tendon sheath may mimic preserved strings of tendon substance, leading to the underdiagnosis of a partial rupture. However, total loss of the fibrillar pattern and irregular nodular appearance of the granulation tissue or synovial thickening are additional findings that help to avoid this pitfall (Figure 4). Sometimes the distal brachial artery adjacent to the biceps tendon may be confused with the hematoma. Weakly pulsatile or heavily compressed brachial artery (Figure 4) requires Doppler angiography. ^13,14

Complete tears are more common than partial tears. Tears almost always occur at or near the distal insertion site on the radial tuberosity, with variable retraction from the radial tuberosity. Longitudinal intratendinous tears or shearing type tears can also occur, and these have been recognized with MSUS imaging. ¹²

Partial ruptures show thinning (attrition of tendon substance, usually chronic) or thickening (from tendin-opathy or granulation tissue) of the distal biceps tendon. As in a complete tear, fluid or hematoma within or adjacent to the partial rupture can occur, but the tendon remains contiguous along its course.

This case illustrates the efficacy of ultrasound in clearly demonstrating the torn and retracted DBT, with the torn end lying over the brachialis muscle. The large hematoma separating the retracted end and the residual stump were depicted accurately. High-frequency transducers provide high-resolution images, readily delineating the fine details of the injured tendon. In addition, the extended field-of-view technique was useful in providing a panoramic view of the injury while demonstrating the level of tendon retraction. ¹⁶ Furthermore, MSUS has several other advantages over other imaging modalities: it is inexpensive, rapid, noninvasive, and does not require ionizing radiation. Dynamic motion study is easy to perform, and direct blood flow mapping is possible with color or power Doppler techniques. Comparison with the asymptomatic side is easier when necessary. The three-dimensional imaging technique, now available in many US machines, may also prove to be a useful method.

Conclusion

The torn DBT in a patient with elbow trauma was clearly visualized with MSUS as a coiled and retracted tendon, avulsed from the radial tuberosity, and separated by a large hematoma. MSUS was useful in confirming the clinically suspected DBT rupture, characterizing it as a full-thickness tear, and assisting in the patient management. *