Supraspinatus, infraspinatus, teres minor, and subscapularis together constitute the rotator cuff tendons.
Supraspinatus tendon: It is the most frequently involved tendon in rotator cuff tears. Tears of the supraspinatus tendon can range from partial to complete tears. This tendon is commonly repaired when indicated, especially in symptomatic or large tears(1). Infraspinatus tendon: It is less frequently torn compared to the supraspinatus tendon, but it is still a common site of rotator cuff pathology. Tears in the infraspinatus tendon can be associated with other rotator cuff tears or occur in isolation. Surgical repair may be considered for larger or symptomatic tears(2). Subscapularis tendon: It is a less frequently torn tendon compared to the supraspinatus and infraspinatus tendons. Certain larger tears are considered for primary repair, especially when conservative treatment does not lead to improvement(3). Teres minor tendon: Teres minor tendon tears are rare, and the tendon is generally intact even in the presence of a massive rotator cuff tear.
Rotator cuff tears are broadly classified into partial and full-thickness tears, and are commonly seen in patients above 40 years of age, causing pain, disability, and reduced quality of life.
Full-thickness tear size definitions:
Small tear: Typically involves a partial discontinuity of the tendon, often less than 1 cm in width. Moderate tear: Larger than a small full-thickness tear but not a full-width tear, usually ranging from 1 to 3 cm in width. Large tear: A full-thickness disruption of the tendon, typically measuring more than 3 cm in width. Massive tear: Involves multiple tendons and may extend to more than 5 cm in width. In some cases, it can lead to complete detachment of the rotator cuff from its attachment site.
Implications of tear size and fatty atrophy in rotator cuff repair:
Tear size:
Smaller tears may be amenable to conservative management or arthroscopic repair, with generally better outcomes. Moderate tears can often be managed with arthroscopic repair, although success rates may be slightly lower than in smaller tears. Large and massive tears usually require surgical intervention due to significant functional impairment and limited healing potential. Fatty atrophy:
Fatty atrophy r efers to the replacement of muscle tissue with fatty tissue, which can occur when the rotator cuff tears are left untreated. Advanced fatty atrophy may compromise the healing potential and functional outcome following rotator cuff repair. The degree of fatty atrophy is assessed using magnetic resonance imaging (MRI) or ultrasound (US) imaging, and can influence the surgical decision-making process.
Most recurrent rotator cuff tears occur within three months(4). Rotator cuff repair is performed to restore shoulder function and relieve symptoms. However, 25% of patients experience pain and dysfunction even after successful surgery(5). Imaging plays an essential role in evaluating patients with postoperative rotator cuff pain. US and MRI are the most commonly used imaging modalities for evaluating rotator cuff. US is often the first-line imaging modality, given its easy availability, lower cost, ability to perform dynamic tendon evaluation, and reduced post-surgical artifacts compared to MRI. It may also be better for earlier diagnosis of smaller re-tears. MRI is superior for assessing the extent of larger tears and for detecting other complications of rotator cuff surgery, such as hardware failure and infection. However, postoperative imaging of the rotator cuff can be challenging due to the presence of hardware and variable appearance of the repaired tendon, which can be confused with a re-tear. This review aims to provide an overview of the current practice and findings of postoperative imaging of the rotator cuff using MRI and US. We discuss the advantages and limitations of each modality, and the normal and abnormal imaging appearance of the repaired rotator cuff tendon.
When imaging postoperative rotator cuff, for an appropriate assessment, one should be aware of the type of surgical repair undertaken. Some of the common techniques are briefly described below.
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.
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).
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.
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).
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).
Massive rotator cuff repairs are defined as full-thickness and full-width tears of two or more tendons of the rotator cuff. Such tears result not only in pain but also in glenohumeral instability, as demonstrated by the high-riding humeral head. These tears are often not amenable to primary repair due to anatomic limitations, chronicity, or extent. In such cases, orthopedic surgeons may elect to proceed with arthroplasty. This is a less-than-ideal option in the younger patient population without glenohumeral arthrosis. Arthroplasty implants have a limited life span, and arthroplasty often results in decreased strength and range of motion compared to the primary repair of the rotator cuff.
In an attempt to avoid arthroplasty, other techniques have been developed, including tendon transfer (most commonly, latissimus dorsi or pectoralis major), patch graft augmentation and bridging, and superior capsular reconstruction.
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).
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).
During subacromial decompression, the undersurface of the acromion is shaved or resected to increase the space and reduce pressure on the rotator cuff tendons. The procedure aims to relieve pain and improve shoulder function in patients with impingement syndrome.
This procedure involves removing a portion of the distal end of the clavicle. The Mumford procedure is commonly performed for patients with acromioclavicular (AC) joint osteoarthritis or AC joint impingement.
The remplissage procedure is performed in conjunction with rotator cuff repair, especially in cases of recurrent shoulder instability with a Hill-Sachs lesion. During the remplissage procedure, the infraspinatus tendon (a rotator cuff tendon) is mobilized and shifted into the Hill-Sachs defect. This action helps to ‘fill’ the defect, effectively preventing the humeral head from engaging the glenoid (shoulder socket) during shoulder motion and reducing the risk of recurrent instability.
MRI is a highly sensitive and specific imaging modality that can provide detailed information about the extent of the re-tear and the status of the rotator cuff repair. However, when compared to the US, MRI is more susceptible to surgical hardware artifacts, more expensive, and not readily available. In addition, it is not possible to obtain a dynamic evaluation on MRI.
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). The thickness, echogenicity, and continuity of the tendons are assessed. The supraspinatus tendon is the one that is typically repaired; thus, even though other tendons are evaluated as part of the examination, this is the one that is given the most attention. The volume of the rotator cuff muscles is also evaluated. To evaluate the integrity of the repair, passive dynamic maneuvers, including abduction and external rotation, are conducted, while keeping the patient’s comfort in mind. Subacromial-subdeltoid bursa and acromioclavicular joint are assessed for the presence of fluid or other post-surgical sequelae.
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).
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.
Both US and MRI play vital roles in the imaging evaluation of postoperative rotator cuff. Recent studies have revealed no significant difference between US and MRI for diagnosing tears in repaired rotator cuff(19). The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for the US in detecting rotator cuff re-tears were 95%, 90%, 97%, 82%, and 94%, respectively(20). However, the correlation between the structural integrity of rotator cuff repair and the clinical outcome remains controversial, and there are studies indicating that the functional outcome is independent of the structural integrity(21).
Imaging evaluation of repaired rotator cuff becomes difficult due to anatomical distortion at the surgical site. Intact repaired tendons appear thickened and heterogeneous on both US and MRI for at least one year to five years postoperatively(18,22,23). These changes gradually regress with the progression of time, with a return to standard fibrillar patterns. However, the suture material and associated graft patches continue to appear heterogeneous and thickened. MRI usually shows susceptibility artifacts related to anchors and sutures that could impair visualization of the repaired tendon, limiting interpretation (Fig. 3). MRI in the early postoperative period shows intermediate or high signal intensity of the repaired tendon on fluid-sensitive sequences, and may reveal a small amount of fluid in the subacromial-subdeltoid bursa, which is considered a normal spectrum (Fig. 14). US has the excellent advantage of dynamic assessment of the repaired cuff’s integrity. This dynamic assessment can be used to evaluate the stability and functionality of repaired tendon while in motion. Similarly to MRI, the variable and heterogeneous appearance of the repaired cuff on US may persist for years after surgery (Fig. 15). There can be discontinuity and irregularity of a few of the repaired tendon fibers, which may represent unrepaired torn fibers that were not possible to repair due to poor quality of tendon tissue(24). Thus, information about the extent and type of surgical repair is needed to avoid overcalling re-tears.
Artifacts due to surgical hardware and postoperative scar tissue can affect how an MRI or US scan looks, and determine its diagnostic capability. Additionally, on US, the patient’s body habitus, fatty infiltration of the deltoid, the operator’s experience, and the equipment being used may all affect the visibility and interpretation of repaired tendons.
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.
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.
Specific US and MRI findings that may be seen in patients with a postoperative rotator cuff re-tear include(25):
Thickening, irregularity, defect, or gap within the rotator cuff tendon (Fig. 17, Fig. 18) Empty trough (site of tendon attachment at the greater tuberosity) (Fig. 19) Recurrent tears tend to get larger and significant Completely or partially avulsed or dislodged suture anchor (Fig. 20) Fluid or other abnormalities in the subacromial space (Fig. 18) Biceps tendinosis
Important US and MRI appearances of a re-tear of rotator cuff repair:
Sometimes, a rotator cuff tear or repair does not impact the biceps tendon, so the surgeon may repair the rotator cuff without specifically addressing the biceps tendon. In such cases, imaging reveals a continuous and clearly defined biceps tendon, making it seem normal.
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).
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.
Radiography, US, and MRI are the imaging modalities frequently utilized to evaluate the rotator cuff following arthroplasty. The supraspinatus is expected to be intact in total shoulder arthroplasty (TSA) and absent in reverse shoulder arthroplasty (RTSA).
The indications for RTSA include:
Massive rotator cuff tears: RTSA is commonly performed in patients with massive, irreparable rotator cuff tears, where the torn tendons cannot be adequately repaired or reconstructed. In such cases, the deltoid muscle, rather than the rotator cuff, is used for shoulder function, allowing for improved stability and function. Rotator cuff arthropathy: The condition occurs when a longstanding rotator cuff tear leads to degenerative changes in the shoulder joint. RTSA is considered when the patient experiences severe pain, loss of function, and poor shoulder mobility. Failed previous shoulder surgery: RTSA may be indicated in patients who have had unsuccessful previous shoulder surgeries, including failed shoulder replacements or rotator cuff repairs. Complex fractures: In elderly patients with complex fractures of the proximal humerus (shoulder bone), where the bone is severely damaged and the surrounding tissues are compromised, RTSA may be a viable treatment option. Proximal humerus tumor: In patients with certain tumors affecting the proximal humerus, RTSA may be used to provide pain relief and functional improvement. Severe glenoid (shoulder socket) deficiency: Patients with significant glenoid bone loss or deformities may be candidates for RTSA, as it can provide better stability and fixation.
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.
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).
The rotator cuff position and movement may vary after arthroplasty. Imaging can be used to determine whether the tendons correctly exhibit the anticipated mobility during dynamic US imaging, indicating proper functioning.
Surgical intervention or long-term rotator cuff disease can cause tendon atrophy or attritional thinning. Imaging, especially US or MRI, can measure the thickness of the rotator cuff tendons and compare it to the other side or to preoperative imaging scans. Tendon atrophy or thinning may indicate chronic degeneration or persistent disease.
The rotator cuff may have undergone repair or reconstruction during various arthroplasty procedures. Like the results seen after a primary rotator cuff repair, imaging can help assess the state of repair and integrity of the repaired or reconstructed tendon. It is possible to see sutures, anchors, or other repair tools, which provide visual cues that surgery was previously performed.
After arthroplasty, the rotator cuff may experience fluid collections or subacromial-subdeltoid bursal effusions. These could be symptoms of bursitis, synovitis, or surgical inflammation. The fluid accumulations can be seen on US or MRI as hypoechoic or hyperintense regions.
Suture anchors and screws, among other surgical devices, can introduce artifacts in imaging studies, resulting in acoustic shadowing or reverberation on US and signal dropouts or distortion on MRI, making it challenging to visualize and evaluate the integrity of rotator cuff tendons.
Scar tissue is formed because of healing. It could be challenging to differentiate between scar tissue and recurrent or residual tears because this scar tissue might change the way the healed tendon and its surrounding components look. It may be a challenge to evaluate the mobility of the rotator cuff tendons if they are encased in scar tissue. It is not unusual to see an apparent full-thickness defect or focal cleft in early postoperative rotator cuff, representing a reparative scar rather than a true re-tear(28). Follow-up US imaging may show the filling of these apparent defects, suggesting routine healing.
The time interval since surgery can impact postoperative rotator cuff MRI results. Due to inflammation and edema, the rotator cuff tendons may seem swollen and disorganized in the early postoperative period. However, the tendons should eventually appear normal, with expected fibrillar echotexture.
The rotator cuff tendon margins should be examined the most carefully. The tendon edges ought to be smooth, and the presence of uneven or ragged tendon edges could indicate a tear.
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).
Understanding the expected time-bound variation of imaging findings post rotator cuff repair is critical to improving the accuracy of diagnosis and avoiding pitfalls and overdiagnosis. Most recurrent rotator cuff tears happen within three months. Therefore, it is essential to have a high index of suspicion during this period for a re-tear in any patient with persistent pain or weakness after rotator cuff surgery. It is important to note that patients with recurrent tears may be asymptomatic. but large recurrent tears are more likely symptomatic. The ability to perform a dynamic evaluation and reduced limitations from artifacts may favor US over MRI in the initial assessment of postoperative rotator cuff, provided that operator expertise exists.