The biceps tendon connects the biceps muscle to the bone. A rupture is a sudden tear that often occurs during heavy lifting or forceful activity. When a rupture is suspected, especially if the physical examination is inconclusive, diagnostic imaging is necessary to confirm the injury. Magnetic Resonance Imaging (MRI) is commonly used because it excels at visualizing soft tissues, including tendons, muscles, and surrounding structures. MRI provides a detailed, non-invasive assessment of the injury’s location and severity, which is crucial for determining the appropriate course of action.
The Necessity of Precise Biceps Tendon Diagnosis
The biceps tendon can rupture at two main attachment points: proximally at the shoulder (Long Head of the Biceps Tendon, or LHBT) and distally at the elbow. Proximal ruptures are far more common, accounting for about 96% of all biceps injuries, and often occur alongside other shoulder pathologies like rotator cuff tears. Distal ruptures are rarer but are considered more functionally significant because the biceps is the primary supinator of the forearm.
A thorough physical examination can suggest a rupture, but it is often insufficient to fully characterize the injury, particularly in cases of partial tears or significant swelling. Imaging is required to definitively distinguish between a partial-thickness tear and a complete rupture. This distinction is important, as the required treatment differs based on the tear’s severity and location. A clear radiological assessment is also needed to guide the surgical plan, especially when the injury is chronic or the patient has a complex medical history.
Specific MRI Protocols: Standard vs. MR Arthrography
The choice of MRI protocol depends on the suspected location and nature of the tear, particularly the need to visualize subtle internal joint structures. A standard MRI uses powerful magnets and radio waves to create detailed images, typically employing T1-weighted and fluid-sensitive T2-weighted or STIR sequences. This protocol is effective for diagnosing complete ruptures, especially for distal biceps tears, where it achieves high sensitivity and specificity.
For a suspected distal rupture at the elbow, a standard MRI is often sufficient, but specialized positioning can enhance visualization. The Flexed-Abducted-Supinated (FABS) view is a dedicated protocol that places the arm in a specific position to optimize the long-axis view of the distal tendon. The FABS view helps distinguish between high-grade partial tears and complete ruptures that might be difficult to characterize on standard imaging planes.
For proximal biceps tears, which involve the tendon’s path through the shoulder joint, Magnetic Resonance Arthrography (MRA) is frequently the preferred technique. MRA involves injecting a Gadolinium-based contrast dye directly into the joint space before the scan. The contrast material outlines the intra-articular structures, providing superior detail for subtle tears and associated pathology.
Contrast enhancement is particularly useful for identifying low-grade partial tears of the LHBT or associated injuries to the glenoid labrum or rotator cuff. Although some studies suggest little difference in diagnostic accuracy for complete tears, MRA better delineates the tendon’s relationship to the surrounding anatomy, making it the protocol of choice for complex shoulder injuries. The injected fluid distends the joint capsule, allowing the radiologist to see small tears or areas of instability that might be obscured on a standard MRI.
Assessing the Extent of Injury
Regardless of the protocol used, the radiologist focuses on several imaging features to characterize the injury. The first is determining the tear’s severity, classifying it as a partial tear (where some tendon fibers remain intact) or a complete rupture (where the tendon is fully separated). On fluid-sensitive T2-weighted images, a complete tear appears as a high-signal, fluid-filled gap between the two ends of the tendon.
A second factor is the degree of tendon retraction, which is the distance the torn tendon end has pulled away from its insertion site. Retraction is measured on the sagittal MRI sequences from the anatomical insertion point (the radial tuberosity for a distal tear or the glenoid for a proximal tear) to the most distal point of the remaining tendon stump. For distal tears, retraction can range significantly, sometimes measuring 6.0 centimeters or more.
The pattern of retraction also provides information. For instance, a distal biceps tendon that is severely coiled or bunched up is sometimes referred to as the “Turtle Neck Sign.” This curled appearance is associated with a complete rupture and an accompanying tear of the lacertus fibrosus, a structure that normally helps prevent significant retraction. The MRI report will also detail associated soft tissue findings, such as edema (increased signal intensity in the surrounding muscle belly) and any hemorrhage or fluid accumulation in the peritendinous tissues.
MRI Findings and Treatment Decisions
The objective data provided by the MRI directly informs the orthopedic surgeon’s treatment plan. Complete ruptures, especially those of the distal biceps tendon, are generally treated with surgical repair to prevent permanent loss of strength in elbow flexion and forearm supination. The degree of tendon retraction measured on the MRI influences the urgency and type of surgery.
For distal tears, the goal is typically to perform a primary repair within about four weeks before scarring and muscle shortening make reattachment without a graft impossible. Lengthy retraction, particularly if the injury is chronic (older than six weeks), increases the likelihood that a tendon graft will be necessary for reconstruction, as primary reattachment may no longer be possible. Conversely, a low-grade partial tear or a complete proximal rupture in a low-demand patient may be managed non-surgically with rest, physical therapy, and pain management. The MRI translates the physical damage into quantifiable metrics, allowing the surgeon to select the most effective treatment pathway.