Role of ultrasound and MRI in the evaluation of postoperative rotator cuff

The traditional surgical procedure for rotator cuff tears is an open repair. To reach the torn rotator cuff tendon, a sizable skin incision must be made. The surgeon identifies the ripped tendon in realtime, after which the repaired tendon is reattached to the bone with sutures or anchors. In contrast to arthroscopic procedures, open repair typically involves larger incisions, and prolonged recovery periods, and is associated with more complications⁽⁶⁾. However, it provides good visualization and direct access to the rotator cuff. Tendon transfer surgery, such a latissimus dorsi or pectoralis major transfer, is also undertaken as an open procedure, to fix an irreparable rotator cuff.

Repairs of large tears with retracted tendons, and poor tissue quality tendons are sometimes technically challenging to perform arthroscopically. Consequently, these tears can be repaired using a mini-open approach, which involves making a vertical split in the anterolateral deltoid muscle to approach the rotator cuff tear.

This is the most preferred repair option nowadays, and is broadly divided into two types: single-row rotator cuff repair and doublerow rotator cuff repair.

Single-row rotator cuff repair

Partial-thickness tears, small full-thickness tears, and subscapularis tears are commonly treated arthroscopically via single-row rotator cuff repair. Following arthroscopic access, the damaged tendon is attended to by removing debris and scar tissue. Then, the tendon is reattached to the greater tuberosity utilizing sutures and anchors arranged in a single row (Fig. 1).

Fig. 1.

The position of the repaired tendon and the quality of the repair can be evaluated radiologically during the postoperative period. Both MRI and US are utilized to visualize postoperative changes. A well-apposed tendon-to-bone interface, and the absence of fluid collections or gaps at the repair site, are good indicators of good repair and tendon healing on both US (Fig. 2) and MRI (Fig. 3)⁽⁷⁾. However, MRI can be affected to varying degrees by artifacts.

Fig. 2.

Fig. 3.

Double-row rotator cuff repair

Larger tears are fixed utilizing a more complex surgical technique called the double-row repair, which seeks to better resemble the natural rotator cuff’s architecture. The damaged tendon is repaired by anchoring the tendon in two distinct locations (medial and lateral) instead of a single tendon row (Fig. 4). Improved biomechanical stability is intended to be provided by applying the double bundle approach, which may also lead to improved functional results^(8,9). Like single bundle repairs, the assessment of postoperative double bundle repairs focuses on the location, integrity, and healing of the repaired tendon. Imaging often reveals two suture anchors, or groups of suture anchors, at the repair site for a double-row repair (Fig. 5).

Fig. 4.

Fig. 5.

A hybrid procedure, known as transosseous equivalent repair, combines the advantages of both open and arthroscopic methods. It tries to mimic the biomechanics of open repair, while achieving the benefits of arthroscopic surgery. The method uses tiny arthroscopy incisions to send sutures through the tendon and tunnels carved out of the humeral head. To replicate the transosseous tunnels utilized in open repair, the sutures are knotted over bone bridges⁽¹⁰⁾ (Fig. 6, Fig. 7).

Fig. 6.

Fig. 7.

In the tendon transfer method, the choice of tendon is dependent on the functional deficit resulting from the tear in question. The most commonly employed tendon transfers are the latissimus dorsi and the pectoralis major. The latissimus dorsi transfer simulates the function of the posterosuperior rotator cuff and augments external rotation. The pectoralis major tendon transfer may be used to mimic the function of the anterosuperior cuff. The sternal head of the tendon is typically employed and augments internal rotation, acting in a similar fashion to the subscapularis tendon. Different techniques for the transfer of graft tendons are available to the surgeon. It is helpful to be familiar with the specific technique when evaluating the postoperative appearance of the repair. The most common complications in tendon transfers include graft tendon tear, infection, or neurovascular injury⁽¹¹⁾.

The MRI and US appearance of a normal transferred tendon is similar to primarily repaired rotator cuff tendons. On MRI, graft tendons are typically low to intermediate in signal on T2-weighted and T1-weighted imaging, often with intermediate signal at the attachment of the tendon due to granulation tissue and scar formation. The fluid-filled defect would be consistent with a tear of the graft tendon. Neurovascular injury is a potential complication, and, on MRI, this may manifest with denervation edema and fatty infiltration⁽¹²⁾.

Patch graft augmentation can be employed to bridge an irreparable tear or defect, or to patch and reinforce a primary repair that may not achieve optimal strength or healing. Patch augmentation may be performed with autografts, allografts (human dermal grafts), xenografts, or synthetic grafts⁽¹³⁾. Graft augmentation uses grafts to reinforce the existing primary repair, with the graft sutured directly to the repaired tendon. Patch graft bridging is used to address an irreparable defect greater than 1 cm, and the graft is sutured to the debrided torn tendon stump and to the insertion site on the bone, forming a bridge between the torn tendon and the original footprint.

On MRI, intact grafts and repaired tendons should be low to intermediate in signal, without fiber discontinuity. Findings such as partial or full-thickness fluid-filled defects, as well as attenuation and laxity of the tendon or graft, are indicative of recurrent tear⁽¹⁴⁾.

For patients with massive rotator cuff repairs and no glenohumeral arthrosis, superior capsular reconstruction has been used to provide glenohumeral stability by preventing superior migration of the humeral head through the torn superior cuff and prevent or reduce the development of rotator cuff arthropathy⁽¹⁵⁾. Currently, the most commonly used graft is the dermal allograft (Fig. 8). In superior capsular reconstruction, the graft forms a bridge from the superior glenoid to the greater tuberosity. In addition to the anchoring of the graft to the superior glenoid and the greater tuberosity, the graft is also sutured to the adjacent remnant rotator cuff tendons (Fig. 9). Potential complications of the procedure include tear of adjacent repaired tendons, re-tear of the anastomosis of the graft to adjacent tendons, and graft detachment from the greater tuberosity or the glenoid (Fig. 10).

Fig. 8.

Fig. 9.

Fig. 10.

The normal appearance of an intact graft on MRI is a low-signal structure without laxity or discontinuity(^12,15). Graft detachment may be accompanied by the laxity of the graft, superior migration of the humeral head, and dislodged anchors. On US, the graft is an echogenic linear structure. US findings of graft failure are similar to the appearance on MRI and include laxity due to graft detachment and hypoechoic fluid at the site of tears in the adjacent tendon. One study of 18 patients with superior capsular reconstruction who received a postoperative ultrasound at one-year follow-up showed that the graft might increase in thickness, particularly at the lateral humeral attachment, and might also show neovascularization⁽¹⁶⁾.

The US appearance of postoperative rotator cuff can vary depending on the time after surgery, type of repair performed, and any complications. Since some voluntary shoulder movement is required for an US study, this should be avoided in the immediate postoperative period.

The rotator cuff tendons are imaged using high-frequency linear transducers (6–15 MHz)⁽¹⁷⁾. Discussed below is a brief overview of the US technique for the assessment of postoperative rotator cuff, which is similar to the protocol used while evaluating the native rotator cuff:

The patient is seated, with the elbow flexed and the arm abducted to 90 degrees. The supraspinatus tendon is evaluated in either Crass or modified Crass positions (Fig. 11). Based on the position being scanned, the torn tendon morphology can differ, with more separation of the tear in the modified Crass position (Fig. 12).

Fig. 11.

Fig. 12.

There can be postoperative inflammation in the bursal space and other soft tissue around the repaired rotator cuff, which can be assessed by color, power, and microvascular Doppler US (Fig. 13).

Fig. 13.

Shear wave elastography has an added value in the follow-up of repaired rotator cuff By helping to evaluate whether the elasticity of the tendon is having a normal or abnormal progression with duration⁽¹⁷⁾.

MRI can evaluate the entire length of the rotator cuff tendons in various planes. Repaired rotator cuff commonly demonstrates increased signal intensity due to postoperative granulation tissue and inflammation rather than a re-tear⁽¹⁸⁾. The protocol used to study postoperative rotator cuff is like that of the preoperative MRI.

In intact rotator cuff repair, the distal end of the reconstructed rotator cuff tendon must be firmly fastened to the bone, covering the newly created trough portion in the greater tuberosity. A well-apposed contact between the restored tendon and the bone surface can be seen and assessed on US and MRI, to confirm the integrity of repair (Fig. 2, Fig. 3, Fig. 12).

Depending on the surgical approach employed, US and MRI may detect the presence of sutures or anchors, which on US appear as hyperechoic structures either inside or near the healed tendon (Fig. 16). They function as reminders of the repair and might support pinpointing the repair site’s position. On T2-weighted MRI sequences, the suture anchors may be seen as small, rounded, or oval structures with low signal intensity.

Fig. 16.

The subacromial-subdeltoid bursa may be thickened following rotator cuff repair (Fig. 14), which is thought to be caused by inflammation and scar tissue production. Sometimes the bursa is excised, which can lead to the pooling of fluid in its place, in the immediate postoperative period.

A partially torn long head of the biceps is sometimes totally released from the biceps anchor. On imaging, this is seen as an empty bicipital grove, and with time the biceps musculature shows fatty infiltration and atrophy.

Biceps tenodesis involves detaching the biceps tendon from its native attachment and reattaching it to another location, usually in the distal bicipital groove or the distal pectoralis major tendon, close to its humeral attachment site (Fig. 23).

Fig. 23.

The reattached biceps tendon should exhibit a secure and stable position in its new place following successful biceps tenodesis. The tendon is visualized by imaging as rigidly fixed to the proximal humerus, typically with suture anchors or other fixation devices⁽²²⁾. The tendon should appear whole and uninterrupted, with no signs of tears or breaks.

Suture anchors or other fixation devices used to secure the reattached biceps tendon to the proximal humerus may be visible through imaging. These devices may appear on US as hyperechoic structures or on MRI as signal voids.

The biceps tendon is encased in a synovial sheath that lubricates the tendon and makes tendon movement easier. The synovial sheath of the reattached tendon may exhibit alterations in shape and thickness after biceps tenodesis, compared to its preoperative state. These modifications can be seen on both MRI and US.

Several characteristics can be observed when examining the imaging findings of the rotator cuff post-TSA or RTSA⁽²⁶⁾.

One of the critical issues for planning TSA and RTSA is the integrity of the supraspinatus and subscapularis, respectively. Postsurgery, imaging examinations can help determine whether the rotator cuff tendon is torn, partially torn, or intact. It may appear thin, but a healthy, undamaged rotator cuff is a continuous, well-defined structure on US or MRI scans, without any signs of rupture or retraction (Fig. 24). Focused abnormalities or disruptions in the tendon fibers can be used to detect partial or complete tears. While an attempt is made to avoid incising subscapularis to approach the joint when performing RTSA, one of the primary challenges in evaluating the subscapularis tendon post-TSA is that the tendon is often incised during the surgical procedure to gain access to the shoulder joint for implant placement. This can result in varying degrees of damage to the tendon, making it difficult to assess its condition accurately. Additionally, the presence of metallic artifacts from the prosthetic implant can obscure the imaging quality in standard radiographic studies, such as radiography. This can limit the visibility of the subscapularis tendon and surrounding structures on MRI.

Fig. 24.

To overcome these challenges, advanced imaging modalities are often utilized for a more comprehensive assessment of the subscapularis tendon post-TSA and post-RTSA. MRI and US are commonly used, as they offer superior soft tissue visualization compared to CT or radiograph, and can help detect subscapularis tendon tears or pathology more effectively(²⁷) (Fig. 25).

Fig. 25.

To overcome the limitations, sometimes examining the rotator cuff tendons using both imaging techniques, including MRI and US, may be needed. This can lessen the effect of artifacts and give a more thorough evaluation of the tendons. The patient’s medical history is beneficial when evaluating postoperative rotator cuff imaging scans. For instance, the probability of a re-tear rises if the patient has a history of recurrent rotator cuff tears.

There are modifications in MRI sequences that usually help to reduce imaging artifacts, including: using fast spin-echo and short inversion time inversion-recovery sequences, increasing bandwidth and echo train length, increasing the matrix and decreasing section thickness, to name a few.

Shear wave and strain wave US elastography are used to predict the outcomes of repaired rotator cuff based on the elasticity of the tendon tissue and demonstrating promising results (Fig. 26).

Fig. 26.