Author(s): Sagar S. Parikh, MD, Laurent Delavaux, MD, Jonathan Wolbert, DO
Originally published: September 20, 2013 Last updated: May 25, 2021
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Disease/ Disorder

Definition

As the key dynamic stabilizers of the shoulder, the muscles of the rotator cuff (ie, supraspinatus, infraspinatus, teres minor, and subscapularis) are susceptible to various degrees of injury. These injuries are described based on location of the lesion, tear pattern, functional impairment and recovery; however, a clear global classification consensus does not exist.38 Injury classification can be described as tendonitis, tendinosis, or tear with a subclassifications of partial or full thickness and incomplete or complete tears depending on degree of injury (Figure 1).

Rotator-Cuff-Figure-1-RC-Tear-2Download

Figure 1-created by Sagar Parikh, MD

By definition tendonitis (acute phase) connotes inflammation of the tendon while tendinosis or tendinopathy (chronic phase) connotes tendon degeneration most commonly caused by  breakdown of collagen protein leading to disorganization of fiber orientation.48  These can be visualized and distinguished effectively with ultrasound.  Tears as mentioned before can either be incomplete tears (partial thickness) or complete tears.

As mentioned before, there is no consensus on a specific classification system for rotator cuff tears (RCTs), however the Snyder Classification for RCTs has been shown to have good reproducibility and interobserver agreement.24   This classification identifies partial tears based on their location–either on the articular (A) or bursal (B) side–and degree of tearing ranging from a normal tendon without injury (0) to a severe tendon injury associated with either a flap tear or significant tendon fragmentation (IV).  Refer to Table 1 for an in-depth explanation of the classification system.24

Rotator-Cuff-Table-1-Snyder-Classification-1Download

An RCT classification put forth by Jon Jacobsen describes RCTs based on their anatomical characteristics visualized through ultrasound.  This classification scheme emphasizes accurate localization of the injury, specifically involvement of the articular or bursal surface, whether the tear is located interstitially within the tendon (i.e., intrasubstance), whether the tear extends from the articular to the bursal surface (i.e., full-thickness) and the relative completeness of the tear (i.e.,   focal tear or full width). 20   

The Patte classification system is useful to determine the degree of muscle and tendon retraction in full-thickness complete tears specifically of the supraspinatus muscle.44 The full classification can be seen in Table 2.  Massive RCTs are usually > 5 cm and involve complete detachment of at least 2 tendons typically the supraspinatus and infraspinatus.1

Rotator-Cuff-Table-2-Patte-ClassificationDownload

Finally, it is important to distinguish between traumatic and non-traumatic rotator cuff tears as it guides treatment options. Surgery is usually indicated in traumatic cases while a trial of non-surgical treatment is warranted in non-traumatic injuries.

Etiology

Rotator cuff injury occurs when any of the 4 muscle-tendon units that surround the shoulder become damaged. Acute tears can result from immediate increased tensile force/overload or by direct laceration. The mechanism of injury in acute RCTs are typically easy to identify by patient history with specific reported incidents followed by onset of pain.  Chronic, non-traumatic tears result from gradual changes from a pre-existing injury or by diminished vascularization because of aging, generalized comorbidities, tobacco usage, as well as physiologic predispositions or aberrant shoulder mechanics.41 Chronic subacromial impingement syndrome is possibly the most common cause of rotator cuff tears.25   Though tears can be found in any of the four rotator cuff muscles, the supraspinatus is the most commonly torn muscle.50

Epidemiology including risk factors and primary prevention

With respect to predisposing factors, advancing age is considered one of the most influential risks.39  RCTs are primarily symptomatic in persons aged 40 and older. The average incidence of RCT reaches 20-30% in patients aged over 40 years; however, it can reach as high as 62% in patients over 80 years of age.  A strong dose association has also been established between smoking history and the development of RC tears.39 There is also a correlation between RCTs and certain systemic conditions such as rheumatoid arthritis and diabetes.49

In addition to degeneration, acute traumatic tears are associated with repetitive overhead motion and previous shoulder dislocation.4 Though RCTs are most common in the dominant limb, there is also a higher prevalence in the contralateral shoulder of a previously injured rotator cuff.39  

Long head of biceps tears and glenohumeral joint abnormalities are associated with RCTs almost 75% of the time.5 Cases of deltoid muscle rupture and/or superior migration of the humeral head may also indicate a high-grade RCT.6  In addition, pectoralis major muscle injury, typically associated with indirect trauma such as from weightlifting, is also associated with some degree of rotator cuff injury.7

Patho-anatomy/physiology

The rotator cuff is composed of 4 separate muscle tendon units (supraspinatus, infraspinatus, subscapularis, and teres minor) originating from various portions of the scapula and inserting into the humerus. The supraspinatus, infraspinatus and teres minor insert onto the greater tuberosity of the humerus, and the subscapularis inserts on the lesser tuberosity of the humerus. Of note, in considering mechanisms of injury, the supraspinatus tendon travels through a confined space above the humeral head, referred to as the subacromial space. Subacromial impingement syndrome (SAIS) is the most common shoulder disorder, accounting for 44-65% of all shoulder pain complaints.47 This occurs as result of inflammation and degeneration of the structures within the subacromial space (supraspinatus tendon and subacromial bursa) by either an intrinsic or extrinsic mechanism.  Extrinsic explanations for SAIS in the literature suggest that narrowing of the acromiohumeral distance (AHD) is a key factor.41 In healthy shoulders, this measures approximately 7-14 mm. Variations in the shape of the acromion have been shown to increase the risk of RCTs by decreasing AHD contributing to impingement of the rotator cuff tendons.40 Acromion morphology can be flat (Type 1), curved (Type 2), or hooked (Type 3). Of note, an increased thoracic kyphosis and protracted scapulae have been shown to narrow the subacromial space, increasing the incidence of tendon injury as a result of mechanical compression.41

On the other hand, intrinsic impingement occurs due to degenerative processes within the tendon itself. 26  The theories supporting an intrinsic mechanism of tendon injury point to the poor vascularization of the distal supraspinatus tendon near its insertion site onto the greater tuberosity.  This so-called “critical zone” of the tendon is usually where injury or tears occur. Injuries in this area can be compounded by patients’ medical comorbidities that may further delay healing and disrupt the organization of the tendon fibers.41

Internal impingement, which also a form of extrinsic impingement, is not necessarily related to AHD. Internal impingement occurs on the articular surface of the tendon, usually between the superior glenoid and humeral head, when the shoulder is in an abducted, externally rotated, and extended position. This shoulder positioning can commonly be seen in volleyball, tennis, swimming, and baseball athletes.

A weakened rotator cuff with a normal deltoid can result in superior migration of the humeral head, allowing the tuberosity to repetitively abut against the coracoacromial arch. This migration can result in further injury to the supraspinatus and may lead to tearing of the tendon. Repetitive traction, friction, and glenohumeral rotation because of upward migration of the humeral head can lead to LHB tendinopathic changes.12

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

The diagnosis of rotator cuff injury at its onset can be challenging because there is a high proportion of patients with mild to moderate disease that may be asymptomatic. (39).  Nevertheless, rotator cuff disease and impingement begins in early adulthood and progresses in subsequent years. According to Neer, the first phase of rotator cuff injury begins with increased edema and microhemorrhages of subacromial bursal tissue and within the rotator cuff tendons. This stage is usually reversible. The second stage involves inflammatory remodeling changes and degeneration of the tendon.  Inflammation can lead to calcific deposits resulting in rotator cuff tendonitis, which will typically be symptomatic between ages 25-40. Finally, in stage three, partial or full rotator cuff tears occur. This generally occurs after forty years of age (Table 3). 27

Rotator-Cuff-Table-3-Neers-ClassificationDownload

Specific secondary or associated conditions and complications

Associated conditions with RCTs and LHB, PM, and deltoid tears include glenohumeral dislocation/subluxation, acromioclavicular separations, glenoid labrum tears, and instability. A significant complication of these conditions (especially in the chronic setting) is adhesive capsulitis.

Essentials of Assessment

History

Essential components of a history include whether the injury occurred acutely or has had a more insidious/chronic course, when the injury occurred, what was the mechanism of injury, the location of the pain/symptoms, how the pain is characterized and if there is any radiating pain. Other important components include prior shoulder injuries, prior shoulder surgeries, what activities or positions alleviate or exacerbate the symptoms, and what treatments and/or interventions have been attempted thus far, and to what benefit.

Physical examination

Examination includes inspection for focal muscular atrophy, bruising or potential bony deformity of the clavicles, AC joints, as well as muscular deformities (i.e., Popeye or Ludington signs). The patient’s cervical spine alignment and scapular positioning should be noted.  Palpation of superficial structures should include the sternoclavicular joint, clavicle, AC joint, coracoid process, supraclavicular fossa, greater and lesser tuberosities of the humerus, LHB in the bicipital groove, spine of the scapula and corresponding RTC musculature. Then, active and passive range of motion, strength, neurovascular testing, and special tests are performed. Special attention should be paid to muscle tone, symmetry, and deformity. An examination of the opposite shoulder should always be performed as a comparison as well as a cervical spine examination, if needed, to rule out spine pathology.

Special testing should include rotator cuff strength (empty can, external rotation, belly/lift-off), impingement testing (Hawkins sign and Neer sign), LHB testing (Yergason and/or Speed tests), and labral testing (O’Brien’s test).

At the beginning stages of supraspinatus tears, Jobe sign, or the empty can sign (PPV 0.84), may be positive. As tears progress, the external rotation lag sign (PPV 1.0) can be used to test the integrity of supraspinatus and infraspinatus muscles. The drop test (PPV 1.0) can distinguish infraspinatus tears from supraspinatus. The internal rotation lag sign (PPV 0.97) can be used to test supraspinatus, as well as the lift-of (PPV 1.0).28 The bear hug test was found to have a sensitivity of 0.60, and specificity of 0.92. 30 The bear hug test can detect subscapularis tears as small as 30%, while the lag-sign becomes positive when more than 75% of the tendon is torn.30

For rotator cuff impingement, the Neer sign has a sensitivity of 0.68 and specificity of 0.69, while Hawkins sign has a sensitivity of 0.72 and specificity of 0.66. The best post-test probability for any degree of impingement can be yielded by combining the Hawkins-Kennedy impingement sign with the painful arc sign, and the infraspinatus muscle test (95%).29

Other rotator cuff tests include the infraspinatus muscle strength test, with a sensitivity of 0.42 and specificity of 0.90. The painful arc sign has a sensitivity of 0.74 and specificity of 0.83. Drop-arm test has low sensitivity of 0.27 but highly specific (0.84).

For long head biceps testing, Yergason’s test can be used. Speed’s test has a sensitivity of 0.38 and specificity of 0.83.29

Since cervical spine pain can closely mimic shoulder pain, The Arm Squeeze Test can be used to evaluate for neck symptoms, with a sensitivity of 0.96 and specificity of 0.91-1.0.18

Rotator-Cuff-Table-4-Dynamic-TestingDownload

Functional assessment

Activities of daily living (ADLs) may be limited in older adults, specifically with self-care activities above shoulder level and behind the back or head.  This includes the ability to dress oneself, reaching for a wallet, combing one’s hair, and donning a jacket. Overhead reaching motions may be pain-limited. Evaluation of biomechanics with the intent to improve form and posture should also be assessed as well.

Laboratory studies

Although laboratory studies are not considered routine, tears are more often seen in those with diabetes, rheumatologic conditions, and other conditions that may affect localized blood flow to the cuff (e.g., small vessel disease).

Imaging

According to New Zealand Guidelines group, plain radiography of shoulder should be ordered when there is a high suspicion for fracture, a dislocated shoulder in someone older than 40 years of age, or when surgery is considered.30 Suggested plain radiography views include anterior-posterior, axillary, and supraspinatus outlet used to examine alignment and degenerative changes about the shoulder. A common finding on plain AP radiograph with a large supraspinatus tear is a high riding humerus.   Ultrasound may be utilized to diagnose rotator cuff and biceps tendon pathology, having the advantage of being quick, noninvasive, dynamic and inexpensive. Ultrasound evaluation of RCTs are best done in both long and short axis to best identify the type of lesion in this manner.  A limitation to ultrasound is its diagnostic accuracy and that it is operator dependent.8 Magnetic resonance imaging (MRI) may be used to diagnose full thickness RCTs and is necessary for evaluation of the proximal long head of bicep tendon as it inserts on labrum which cannot be assessed with Ultrasound. MRI arthrography of the shoulder is the criterion standard performed when there is clinical suspicion of a full thickness RCT and/or a labral tear or post-operative complications. In one retrospective study, US identified rotator cuff tears with a sensitivity of 0.88 and specificity of 0.89 in comparison to MRI which had a sensitivity of 0.91 and specificity of 0.84.19 Therefore, US is an important imaging modality to evaluate for RTC tears and pathology prior to obtaining an MRI.19

Supplemental assessment tools

The Western Ontario Rotator Cuff Index (WORC) is a well-validated, condition-specific, self-reported assessment tool designed to assess quality of life in patients with shoulder complaints secondary to rotator cuff disease. It comprises 21 visual analog scale items in 5 domains: physical symptoms, sports/recreation, emotions, lifestyle and work.9-10 Additionally, another common shoulder assessment tool is the Penn Shoulder Score, a 100-point shoulder-specific, self-reported questionnaire consisting of 3 subscales of pain, satisfaction, and function.16

Patient outcomes can also be assessed with the Simple Shoulder Test (SST). Patients without RTCs typically have lower SST scores than those with RCTs. Restrictions in ADLs were greater in patients with higher SST scores and associated RCTs.15

Early predictions of outcomes

Conservative treatment is reasonable for a partial tear or if circumstances such as chronicity of the injury, severe retraction or patient comorbidities preclude surgery.  Surgical intervention should be considered for younger patients with acute tears, particularly traumatic ruptures11. Surgical success is reduced when fatty infiltration or RCT retraction is present. Recreational athletes have a good prognosis for return to sport, but return to prior level of play is reduced in elite overhead athletes. PM tears in older, sedentary patients or other proximal muscle belly tears are usually treated non-surgically. In other types of PM tears or with younger patients, surgical intervention results in increased functional outcome.12

Social role and social support system

Rehabilitative services designed to improve ADLs are imperative for successful outcomes.  Injury prevention must include strengthening the dynamic and static muscle stabilizers, often with the assistance of physician directed physical or occupational therapy. Physicians should encourage family and friends to assist with more complicated ADLs and to reinforce the importance of adherence to a long-term treatment plan including therapies, home exercises and restrictions put in place to prevent further injury or functional decline.

Professional Issues

Developing a strong working relationship with your radiology and orthopedic colleagues will facilitate initiation of diagnostic and treatment strategies and improved outcomes. Treatment algorithms are not necessarily agreed upon across specialties which may cause confusion especially in management of partial width tears. One algorithm is the 50% rule, which states that tendon and ligament injuries with involvement of less than 50% are best treated by non-operative management. Thus, determining the size of such tears can allow physiatrists to quickly determine if a patient can rehabilitate an injury or will require surgical referral.13 One quick method of determining the size of such tears is through musculoskeletal ultrasound. Though many physiatrists are trained in musculoskeletal ultrasound, musculoskeletal ultrasound evaluations conducted by physiatrists in-office vs. a radiologist may not always be considered official diagnostic studies in some insurance or hospital networks. Thus, it is felt by many in the field that the physiatrist, should they wish to make such determinations, establish their credentials for diagnostic ultrasound through accreditation and/or board certification.

Rehabilitation Management and Treatments

Available or current treatment guidelines

Current treatment guidelines are based on the degree of tendon tear and location. If there is not a complete or full thickness tear, initial treatment involves patient education, activity modification, physical therapy, pain control with analgesic medication, and possible corticosteroid injections.

At different disease stages

Non-operative management is typically recommended as an appropriate strategy in the first few months after a mild-to-moderate injury.  Non-operative treatments may include the use of anti-inflammatory medication and a physical therapy program focusing on restoring pain-free range of motion and gradually progressing to rotator cuff and periscapular muscle strengthening exercises.  If the patient fails to make progress after several weeks, a subacromial corticosteroid injection (i.e., in the setting of subacromial impingement) may provide significant pain control and allow progression in physical therapy.

Most shoulder RCT rehabilitation programs, especially those at home with therabands, emphasize open kinetic chain (OKC) exercises such as dynamic external rotation and/or shoulder abduction keeping the theraband affixed to an anchored object such as a closed doorknob. Closed kinetic chain exercises are also used to promote dynamic joint stability. Other rehabilitation strategies include correction of kinetic chain deficits, muscle recruitment patterns, posture, and scapulohumeral kinesis. This is followed by proprioceptive and neuromuscular training, then integration of the entire kinetic chain into occupational and sport-specific training. OKC exercises are essential to regaining high demand functionality, as in overhead throwers.

Corticosteroid injections can be used for rotator cuff partial tears that do not improve with non-operative treatment (>1-2 months).  Injections may also be used for patients with acute shoulder pain thought to be due localized inflammation within the subacromial/subdeltoid bursa or rotator cuff.  They can also be utilized in the setting of full thickness RCT tears in patients who are not surgical candidates. Though widely performed, the use of corticosteroid injections has been called into question recently secondary to their potential to interfere with the proliferative phase of healing.45 Furthermore, there exists the potential of chondrotoxicity with the use of certain local anesthetics (i.e., bupivacaine) when administered as part of the injectate.  When choosing a local anesthetic, lidocaine is preferred.21 Injections can be done by landmark or anatomic guidance or with the assistance of ultrasound guidance. Ultrasound guided injections are increasingly becoming the standard of care as they have been shown to have superior accuracy and efficacy when applied to almost all shoulder girdle injections.43  Regenerative medicine injections such as platelet rich plasma (PRP) have been gaining favor in the treatment of RCT tears with respect to clinical improvement in pain and decrease in re-tear rates; however, more Level 1 evidence is needed.  36

In cases of calcific tendonitis, ultrasound guided percutaneous barbotage and aspiration is an option when non-operative management strategies including anti-inflammatories, physical therapy and corticosteroid injections have failed.22

If there is no improvement after 3 to 6 months of therapy, surgical consultation for operative repair is recommended. Traumatic rotator cuff tears are usually treated surgically. Chronic, full width RCT tears are treated surgically if they are symptomatic. There is weak evidence for surgical repair of chronic partial rotator cuff tears. There is weak consensus evidence on negative outcomes in diabetics, smokers, patients with previous shoulder injection, or cervical pathology. There is moderate consensus on negative outcomes for patients on disability.33

A RCT is considered irreparable if the defect cannot be closed operatively or if repair will lead to structural failure.  Imaging findings suggesting irreparability of the RCT include static superior subluxation of the glenohumeral joint with an acromiohumeral interval of less than 7 mm or fatty infiltration of the involved rotator cuff muscle.1

Coordination of care

Outcomes are improved when there is communication between all members of the care team. This includes the physical therapist, physician and patient.  Pertinent diagnostic results and a clear course of treatment should be explained to all members of the team. Facilitating a smooth transition of care between different members of the treatment team and educating the patient on the proper home exercise regimen is essential for a successful outcome.

Patient & family education

Patients should be educated on the various treatment options available to them and recovery timeline for their injury. Explaining the differences between full width versus partial thickness/ width RCT tears is important to modulate patient expectations.  Emphasizing compliance with  patients’ home exercise program will help transition to a long-term self-management.14

Emerging/unique interventions

PRP has gained substantial coverage in the media and popularity among professional athletes seeking earlier return to play. However, as stated above, adequate Level 1 research is lacking. While earlier studies found no benefit for the use of PRP in the setting of RCT repair (34, 35, 36), one randomized study showed similar results of PRP vs corticosteroid injections into the subacromial space 37 .  Newer studies have shown clinically relevant benefits in the form of pain relief.46 

Regenerative treatments using bone marrow autologous cells concentrate (BMC) have been emerging for treatment of shoulder osteoarthritis and rotator cuff tendinopathy. Even though BMC has showed promise in one multi-center prospective study, the results have yet to be reproduced.  Moreover, the study was funded by a party with financial investment in BMC.23

For patients that have failed non-operative therapy and would like to avoid surgery, certain regenerative medicine treatments such as PRP and BMC may be considered. However, patients need to be reminded that these are experimental treatments with potentials for harm.

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

For young, overhead athletes, restoration of pain-free range of motion and rotator cuff muscle strength is considered best practice prior to letting these individuals return to sport. Sport-specific or work-specific exercises must be included at the end of rehabilitation to complete the treatment and prevent future injury. Consider imaging and surgical consult early for younger patients with acute injuries and loss of range of motion.

Cutting Edge/ Emerging and Unique Concepts and Practice

Musculoskeletal ultrasound has become a popular imaging modality for direct visualization of the rotator cuff.17 Ultrasound has the advantage of being a quick and dynamic technique and allows for image-guided injections. However, the technique is based on operator experience.8  As mentioned above, US guided injections have been shown to have better accuracy and efficacy in the shoulder.

Cutting-edge concepts in tendon healing include extracorporeal shockwave therapy (ECSWT), regenerative therapies (i.e., PRP), and tenotomy with and without PRP. Each intervention shows some promise for pain and healing; however, the evidence remains inconclusive.34,35,36

Gaps in the Evidence- Based Knowledge

One question that remains to be answered is whether PRP or ECSWT play a role in treatment of partial RCT tears needs to be further defined, as does the role of biologics, such as PRP and stem cells in the setting of frank tears.34,35,36

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Original Version of the Topic

Jason L. Zaremski, MD, Kevin Vincent, MD. Shoulder tendon and muscle injuries. 9/20/2013.

Revised Version(s) of the Topic

Tariq Hilal, MD. Shoulder tendon and muscle injuries. 4/4/2017

Author Disclosures

Sagar S. Parikh, MD
Nothing to Disclose

Laurent Delavaux, MD
Nothing to Disclose

Jonathan Wolbert, DO
Nothing to Disclose