Preoperative Assessment of Massive Rotator Cuff Tears: Choosing Ultrasound or MRI

Before deciding on surgery for a massive rotator cuff tear, imaging has two tasks: establishing how much of the cuff is torn and assessing whether the torn tendons can be sutured back to their original attachment.

Ultrasound and MRI can both detect rotator cuff tears and are highly accurate for full-thickness tears, but they do not provide exactly the same information.

High-quality musculoskeletal ultrasound is valuable for quickly establishing whether the cuff is torn. When a massive tear is suspected and the choices include direct repair, partial repair, superior capsular reconstruction or other treatment, MRI usually provides more complete preoperative information.

The rotator cuff comprises the tendons of the supraspinatus, infraspinatus, teres minor and subscapularis. They surround the humeral head, help produce shoulder abduction and internal and external rotation, and keep the humeral head stable within the glenoid.

There is no universally agreed definition of a massive tear. One traditional definition is a tear measuring more than 5 cm across; another common definition is involvement of at least two rotator cuff tendons.

Tears may also be classified by location, including posterosuperior and anterosuperior patterns. Chronic massive tears often involve tendon retraction, muscle atrophy and fatty infiltration, all of which make repair more difficult.

For a typical rotator cuff injury, identifying the location, size and depth of the tear is already important. With a massive tear, the surgeon must answer a more complex question: can the tendon be brought back to the greater tuberosity and securely fixed?

A tendon torn for years may gradually retract towards the scapula. As its muscle loses normal mechanical loading, it may atrophy and muscle tissue may progressively be replaced by fat. The longer these changes persist, the more difficult recovery generally becomes. A massive tear can also allow the humeral head to migrate upwards, narrowing the distance between the acromion and humeral head. Further progression can lead to cuff tear arthropathy.

Musculoskeletal ultrasound directly visualises structures including the supraspinatus, infraspinatus, subscapularis and long head of the biceps tendon. The examiner can also ask the patient to rotate the shoulder and observe the relationship between the tendons and subacromial structures during movement.

In experienced hands, ultrasound is highly effective at identifying full-thickness tears. A systematic review of 62 studies involving 6,007 patients reported approximately 96% sensitivity and 93% specificity for full-thickness tears; for partial-thickness tears, sensitivity was approximately 84% and specificity 89%.

Another systematic review in 2021 directly compared ultrasound and MRI and found no significant difference in accuracy for full- or partial-thickness supraspinatus tears, provided ultrasound was performed by experienced examiners.

Its main advantage is convenience. The examination is relatively quick, uses no radiation, can be repeated and usually costs less than MRI.

Ultrasound is especially useful for patients with certain medical devices that prevent MRI, severe claustrophobia, or long local waiting times for MRI.

It also allows dynamic examination: while the patient moves the shoulder, the examiner can assess tendon gliding, subacromial impingement, stability of the long head of the biceps tendon and the subacromial bursa. MRI is usually performed with the patient still and cannot provide the same real-time movement information.

MRI shows the cuff tendons and muscles, long head of the biceps tendon, articular cartilage and surrounding soft tissues together. It also allows a systematic assessment of several factors that influence the surgical plan:

After a rotator cuff tendon detaches from the humerus, the muscle gradually pulls the torn end medially. Retraction generally increases with time.

MRI commonly uses the Patte classification to describe retraction. In simple terms, the farther the torn end is from its original attachment, the farther it must be brought back during surgery and the greater the potential tension on the repair.

If the tendon has retracted to the glenoid or even farther medially, a complete direct repair becomes substantially more difficult.

After a cuff tendon tears, its muscle gradually loses normal loading, and some normal muscle tissue may be replaced by fat. This is called fatty infiltration.

Clinicians commonly assess this using the Goutallier classification, from grade 0 to grade 4. Higher grades indicate a greater proportion of fat within the muscle. The supplied material notes that when fat exceeds muscle tissue, muscle function may undergo severe changes that are difficult to reverse.

The supraspinatus can atrophy markedly after a massive tear. The tangent sign on oblique sagittal MRI images helps assess the degree of atrophy.

The clinician draws a reference line on a specific MRI slice. If the supraspinatus muscle belly has become substantially smaller and lies below that line, the tangent sign may be positive.

Early clinical studies found an association between a positive tangent sign and greater difficulty achieving direct cuff repair.

However, one measure alone cannot determine the treatment plan. Clinicians usually consider the tangent sign together with Goutallier fatty infiltration, Patte retraction, tear extent and patient age.

An experienced ultrasound examiner can identify full-thickness tears, their extent, some tendon retraction and dynamic findings, as well as certain changes in muscle structure.

For massive tears, however, surgeons often need precise assessment of the tendon’s retracted position relative to the glenoid and the severity of fatty infiltration and atrophy in the supraspinatus and infraspinatus. Standardised assessment of these factors currently relies mainly on MRI.

Therefore, if ultrasound has identified a very large full-thickness tear and surgery is planned, an additional MRI usually remains useful.

If a high-quality MRI clearly demonstrates a massive tear and adequately shows its extent, retraction and muscle condition, the surgeon can usually plan the next steps from that MRI.

Ultrasound can still add information in certain situations: dynamic assessment of subacromial impingement, focused examination of the long head of the biceps tendon, compromised MRI image quality, or repeated postoperative assessment of continuity of the repaired tendon.

The examinations therefore overlap in some respects, while each has situations where it is particularly useful.

For an initial assessment of whether a full-thickness tear is present, ultrasound may already provide enough information.

If ultrasound suggests a massive tear and the patient is considering surgery, completing an MRI is usually worthwhile.

X-rays do not clearly show the cuff tendons themselves, but they demonstrate bony structures. In massive tears, they help assess upward migration of the humeral head, marked narrowing of the subacromial space, osteophytes and established glenohumeral degeneration.

If a massive tear has progressed to substantial cuff tear arthropathy, treatment may shift from direct cuff repair towards other options, such as reverse total shoulder arthroplasty.

Preoperative assessment therefore often combines X-rays for bone and joint evaluation with MRI for the cuff and muscles, rather than requiring a rigid choice between ultrasound and MRI.

Ultrasound can be considered first when symptoms have recently begun and the main question is whether the cuff is torn; an experienced musculoskeletal examiner is available; a quick, lower-cost initial assessment is desired; MRI cannot be performed; or dynamic assessment is needed.

In patients who suddenly cannot raise the arm after a clear injury, ultrasound can also rapidly identify a large full-thickness tear.

If the tear proves extensive and surgery is subsequently planned, adding MRI for surgical planning is usually more appropriate.

MRI usually provides more complete information when a massive tear is strongly suspected, symptoms are longstanding, active arm elevation is markedly limited, or surgical options are being discussed.

MRI is particularly valuable when the following questions need answering:

Can the tendon be brought back to its attachment? Is retraction severe? How advanced is muscle atrophy? What is the fatty infiltration grade? Are the subscapularis and infraspinatus also involved? Has the humeral head migrated upwards?

These findings directly influence discussion of complete repair, partial repair, patches, superior capsular reconstruction, tendon transfer or reverse shoulder arthroplasty. Massive tears have several treatment pathways, requiring individual assessment of cuff quality, tear extent, fatty infiltration and the patient’s functional needs.

Ultrasound’s main limitation is operator dependence. Examination quality can differ substantially between an experienced musculoskeletal examiner and a general examiner. Deep structures, complex multitendon tears and severely retracted tendon ends are also harder to visualise fully.

MRI takes longer and usually costs more. Some patients with certain metallic or electronic implants cannot undergo it, and severe claustrophobia can make conventional closed-bore MRI difficult to complete.

MRI is not infallible either. Scan quality, shoulder positioning and interpretation experience can affect the result, and final repairability may still require direct assessment during arthroscopy.