Approximately 25% of individuals show full-thickness rotator cuff tears in their 7th decade, and this proportion increases to 50% after 80 years of age. Symptomatic tears are a source of significant morbidity. Rotator cuff tears can be classified as partial and full-thickness tear. The partial thickness tear is further classified as articular side or bursal side. If the full thickness tear is large enough to be retracted more than 5 ㎝ medially, it classified as massive tear Optimal management of rotator cuff abnormalities depends on a variety of factors, such as the presence and severity of an impingement, the degree of tendon damage and individual functional demands. Non-surgical management remains the mainstay of treatment for rotator cuff tears. The physical therapy concentrating on posterior capsular stretching, scapular stabilization, and progressive rotator cuff strengthening as well as medication or subacromial steroid injection could be applied first over a 6-month period.

Surgical treatment for Rotator cuff tear can be classified as open surgery, mini-open surgery, and arthroscopic surgery based on surgical approach, or as debridement, decompression, and repair based on purpose. Since the mid-1990s, the repair of full-thickness rotator cuff tears has undergone a transition from open techniques to combined open and arthroscopic methods (mini-open repair) to exclusively arthroscopic repairs. As reports demonstrated patient outcomes as good as or better than those obtained with open repair, the general consensus emerged that arthroscopic rotator cuff repair was a successful operation. High initial fixation strength, mechanical stability and biological healing of the tendon-to-bone interface are the main goals after rotator cuff repair surgery. Improvements in surgical techniques have led to the development of new strategies that may allow a tendon-to-bone interface healing process, rather than the formation of a fibro-vascular scar tissue.

1. Indications and contraindication

The primary indication is a symptomatic rotator cuff tear (full thickness or partial thickness tear more than 50% of the tendon thickness) confirmed on imaging with activity-related pain, night pain, and loss of function unresponsive to non-operative treatment. It should be emphasized to patients that results of surgical repair are more predictable for pain relief than for restoration of strength or function. Lack of strength alone is less of an indication; however, strength can be improved after surgical repair. Aggressive surgical treatment in younger or high-demand patients is increasingly recommended, based on the likelihood of tear progression and knowledge that smaller tears have increased intrinsic healing potential. Consider distal clavicle excision if there is tenderness over the acromioclavicular (AC) joint and/or inferior osteophytes (from radiographs) possibly contributing to impingement syndrome. In general, Irreparable rotator cuff tears are as follows; cuff arthropathy, severe muscle atrophy and fatty infiltration based on the Goutallier classification, retraction to the level of the glenoid, and elderly patients with poor cuff tissue and healing potential

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2. Procedure

Typical components of arthroscopic rotator cuff repair are as follows; Inspection of glenohumeral joint, subacromial space inspection, subacromial decompression, tear classification and measurement, assessment of rotator cuff tendon reparability, cuff mobilization, greater tuberosity repair site preparation, anchor placement, suture placement, and knot tying.

Subacromial decompression

It means the coracoacromial ligament release, acromioplasty, and bursal debridement. Among these, there are some controversy about the indication of acromioplasty. At the present time, the two most common indications for performing an acromioplasty are subacromial impingement refractory to non-operative care including supervised physical therapy, injections, and activity modification for a minimum of 6 months. And the American Academy of Orthopedic Surgeons clinical practice guidelines for the treatment of rotator cuff tears do not recommend routine acromioplasty during rotator cuff repair. The goal of the acromioplasty is to achieve a flat type I acromion morphology to reduce abrasion of the repaired tendon. Only if the patient has symptoms consistent with acromioclavicular joint arthritis based on the preoperative history (pain localized to the acromioclavicular joint with cross-body adduction or behind-the-back internal rotation) and examination (acromioclavicular joint tenderness on palpation), does surgeon usually perform a distal clavicle resection. Advantages of performing an acromioplasty include improved arthroscopic visualization and ability to control bleeding in the subacromial space as well as an increase in the local concentrations of growth and angiogenic factors, potentially improving the healing environment. Possible disadvantages include weakening of the deltoid origin, a risk of anterosuperior instability in the presence of a failed rotator cuff or irreparable tear, and adhesions between the raw exposed bone on the undersurface of the acromion and the underlying tendon can form, which in turn can limit smoothness, motion, comfort, and range of motion.

Tear characteristics assessment

Tear characteristics are identified including medial retraction, tissue thickness and quality, and tear geometry and asymmetry. Crescent-shaped, U-shaped, L-shaped, and reverse L-shaped tears may be identified, and the geometry of the tear will guide the mobilization techniques used. For the articular-surface partial-thickness rotator cuff tear, treatment options include debridement only, debridement with subacromial decompression, and cuff repair.

l Cuff mobilization It is needed If the tear cannot be reduced to its footprint without excessive tension. Using the thermos-ablation device, the torn tendon can be released from the surrounding tissue on the glenoid and subacromial aspects. Release of the coracohumeral ligament is often very helpful in increasing mobility of the torn rotator cuff.

Repair techniques

Frequently used techniques can be classified as single-row and double-row anchor repairs. Anchors are available in four different materials: metal, non-absorbable plastic, bioabsorbable plastic, and allograft bone. The double-row repair was initially described with a medial row of anchors with sutures in a mattress configuration and a lateral row of anchors with sutures in a simple configuration, but subsequent studies showed limited contact pressures between tendon and bone compared with newer “double row” techniques. One of the more recent double-row techniques that has gained popularity is the trans-osseous equivalent (TOE), otherwise known as the “suture bridge” technique, which was developed to optimize footprint contact area, pressure, and pull-out strength. The TOE technique uses a medial row of suture anchors and a lateral row of knotless anchors. The double-row techniques, including the TOE technique, are significantly stronger than single-row repairs in time-zero cadaveric studies, and several studies have shown higher rates of healing. For massive tear, patch grafts (allogenic freeze-dried tissues, artificial synthetic grafts, porcine small intestine submucosa, or grafts such as the long head of the biceps) or local tendon transfers (subscapularis, latissimus dorsi) can be utilized.

3. Complication

Complications of rotator cuff repair are numerous and include recurrent tear, displaced or broken sutures, muscle atrophy and fat infiltration, nerve injury, deltoid dehiscence, recurrent subacromial spur, a high riding humerus, glenohumeral osteoarthritis, shoulder stiffness or adhesive capsulitis, chondrolysis, and infection. The overall mean complication rate of arthroscopic repair is 10.6% in one series), which is similar to the reported complication rate of 10.5% after open repair. Anatomical failure with re-tear is the most common. Persistent pain may be caused by non-healing of poor-quality cuff tissue, structural failure, inadequate decompression, missed acromioclavicular arthritis, and/or biceps pathology. Shoulder stiffness or frozen shoulder is also one of the more common complications, ranging from 2.7% to 15%. The area of contracture is frequently within the glenohumeral joint, indistinguishable from idiopathic adhesive capsulitis. It may be caused by over-tensioning the repair or prolonged immobilization. Single-row repairs resulted in significantly higher re-tear rates compared with double-row repairs, especially with regard to partial-thickness re-tears. However, there were no detectable differences in improvement in outcomes scores between single-row and double-row repairs. Risk factors for developing a complication: large (3–5 cm) rotator cuff tears; more fatty infiltration; advanced age.

1. Technical consideration

To avoid the metal artifact, lower magnetic field strength, increasing the bandwidth, using a larger matrix size, thinner slices, lower time-to-echo (TE), and swapping the phase encoding direction to reorient the area affected by artifact are recommended, if metallic anchors were used. Gradient recalled echo (GRE) and spin echo spectral fat saturation should be avoided, Special pulse sequences such as Slice encoding for metal artifact correction (SEMAC) or multiple-acquisition with variable resonances image combination (MAVRIC) may be useful in this situation. With MR arthrography, post-operative inflammation and scarring may be distinguished from recurrent partial articular-side tears, a distinction not easily made by non-contrast fluid sensitive sequences. Hence, although MRA is not advocated at some centers, many authors suggest MR arthrography as a useful tool to help image the post-operative patient successfully. However, conventional MR has been widely used for comprehensive evaluation of post-operative shoulder after rotator cuff tendon repair surgery.

2. Expected post-operative findings

Osseous finding

Mild bone marrow edema-like high signal intensity area may be present up to 5 years after surgery in asymptomatic patients who have undergone rotator cuff repair. Additionally, osteolysis or cyst-like area around bioabsorbable suture anchors are expected reactions. These findings may double in size at 6 months, but should eventually stabilize and become replaced with bone at 2 years. The undersurface of the acromion may be flattened after acromioplasty, and the humeral head may be slightly elevated.

Soft tissue finding

The normal postoperative appearance of rotator cuff repair on MRI includes regular or irregular morphology of the tendon with thickening or thinning, intermediate to low signal intensity within the tendon secondary to granulation tissue and fibrosis, and bursal fluid. Intermediate increased signal within the tendon can persist for several months to a year and should not be misinterpreted as a sign of tendinosis or re-tear. Tendon-to-bone healing in clinical rotator cuff repair occurs through scar formation, without recreation of the normal histologic attachment seen in native cuffs. Scar deposition can be substantial and cause tendons to lengthen, a finding that has been suggested to explain degenerative muscle changes and abnormal tendon architecture after repair. Within 3 months of operating, tendons appear most disorganized compared with native tendons, there can be increased signal within the repaired cuff. With time, the development of fibrotic tissue will yield areas of low signal intensity on all sequences. Of note, only 10% of repaired tendons demonstrate normal signal intensity on MRI. It is also important to note that a portion of a torn tendon may purposely be left unrepaired during a rotator cuff repair usually because of poor tissue quality. For the massive rotator cuff tear repair, suspension bridge repair in which complete coverage is not essential to convert debilitating tears into functional cuff tears, can be effective, and this fluid-filled intra-tendinous gap should not be misinterpreted as a recurrent tear With surgical disruption of the tissues around the rotator cuff, the absence of subacromial peribursal fat is a common but clinically irrelevant finding. Similarly, fluid in the subacromial bursa is a normal post-operative feature and cannot be used reliably as a secondary sign of a full-thickness tear or bursitis. Fluid in the subacromial bursal region might persist for many years. Additionally, the presence of contrast extravasation into the subacromial-subdeltoid bursa in isolation without a visible tendon defect on MR arthrography does not always indicate a rotator cuff tear, because the rotator cuff repair is not a water-tight one.

3. Imaging of complication

Recurrent rotator cuff tear

Most recurrent tendon tears occur between 6 and 26 weeks after repair, and has variable causes, including suture-bone or suture-anchor pullout, suture breakage, knot slippage, tendon pullout, poor quality tendon or bone, muscle atrophy, inadequate initial repair, and improper physical therapy. Recurrent tears usually occur at the tendon–bone interface, but they can also occur approximately 1.5㎝ medial to the reattachment site, possibly because of increased tension after reattachment in a tendon that contains intrinsic abnormal architecture. The factors that contribute to recurrent rotator cuff tearing can be divided into those extrinsic to the cuff (most notably, impingement) and those intrinsic to the cuff (age-related degeneration, hypovascularity and inflammation, among others). Some factors are identifiable by imaging, including suture failure, suture anchor displacement and re-formation of a subacromial spur, but the rotator cuff might also re-tear because of too aggressive or inappropriate physical therapy. Only 10% of tendons demonstrated normal low signal intensity. However, if there is unequivocal full-thickness (especially greater than 1 cm) fluid signal traversing the entire repaired tendon at any time point, a retear can be diagnosed. Another sign of recurrent tear includes retraction of the tendon. Progression of a fluid-filled gap and tendon retraction over time is also an indication of failed rotator cuff repair. Loosening of hardware with displacement of a suture or suture anchor may also indicate a re-tear. Often there may be healing granulation tissue within the area of tendon repair, which can mimic fluid within a re-tear; therefore, one must keep this into consideration. There is an oblique linking of two related but not truly comparable concepts: clinical outcome and anatomic healing. The presence of a recurrent tear might not generate symptoms, even when the tear is of full thickness in extent, although the size of the tear is probably related to the development of symptoms. The morphologic alterations of a post-operative rotator cuff might persist for several years after surgical repair, with 20%–50% of tendons having a visible tendon defect for years. There are also several studies with high-levels of evidence that have shown a lack of correlation between recurrent tear and clinical or functional outcomes. The reason for this discrepancy is unclear and remains an area of intense study.

Adhesive capsulitis and post-operative stiffness

This complication usually occurs in the short-term perioperative period. The incidence of adhesive capsulitis varies between 2.7% and 4.9 %. The thickening of the coracohumeral ligament and the joint capsule in the rotator cuff interval, and the complete obliteration of the fat triangle between the coracohumeral ligament and the coracoid process, are the characteristic MRI findings for adhesive capsulitis in the pre-operative shoulder, and may in postoperative shoulder, too.

Problems of suture anchor

Malpositioning of a suture anchor can result in persistent pain after surgery, serious cartilage damage, decreased range of motion and failure of the reconstruction, mandating revision surgery. Bioabsorbable suture anchor can lead to cyst formation, soft-tissue inflammation, and local osteolysis or foreign body granulomas. On MRI, synovitis and related conditions appear as synovial thickening with enhancement and joint effusion.

Deltoid dehiscence

Most cases of loss of deltoid function result from iatrogenic injury during shoulder operations, including open rotator cuff repair, acromioplasty, arthroscopic decompression and arthroscopically assisted mini-open procedures. On MRI, this dehiscence is identified by retraction of the deltoid, with fluid filling the defect. If the detachment is chronic, atrophy is manifested by a decrease in muscle bulk and fat replacement.

Radiologists should understand and pay great degree of attention on the technical aspects of the operation, such as anchor types, suture patterns, suture materials, and instruments as well as expected and abnormal MR findings when read the post-operative MRI after rotator cuff repair surgery.