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Lesion/Condition Name: rotator cuff tendinopathy

What is it?
The rotator cuff is composed of four muscles, supraspinatus, infraspinatus, teres minor, and subscapularis, each of which is attached to the humerus via a tendon. The supraspinatus muscle, responsible for abduction and external rotation of the shoulder, is the biggest component of the rotator cuff. When there is an injury to the supraspinatus tendon, usually as a consequence of overuse, degeneration of the collagen fibers of the damaged tendon with increased fibrosis and neovascularization of the surrounding matrix results in clinical symptoms of tendinopathy [22].

Synonyms: Rotator cuff tendonitis

ICD-0 code: 726.10

Mechanism of Injury:
Although the exact pathophysiology of rotator cuff tendinopathy remains unclear, several factors were found to be involved in its mechanism. As supraspinatus makes up the largest component of the rotator cuff, most rotator cuff injuries involves often damage to the supraspinatus tendon. In addition to the increased tensile overload on the tendon, usually with overhead motions such as throwing or reaching, causing over-stretching and microtears of the collagen fibers, a zone of avascularity at the site of injury created by vascular compromise further exacerbates process of degeneration. Similar to the mechanics responsible for shoulder impingement syndrome, close bony landmarks including acromion, coracoaromial ligaments, coracoid process, and acromioclavicular joint may cause compression and irritation of supraspinatus tendon from a decreased distance between the undersurface of these structures and head of humerus, leading to development of tendinopathy [22].

Risk Factors:
Working population with repetitive overhead activities, for example athletes who specialize in swimming, tennis, golf, throwing, or weightlifting, are at greatest risk. Other comorbidities including old age, vascular diseases ie DM, and connective tissues disease ie RA, Marfan, Ehlers-Danlos can contribute to tendon pathology [7,16,23].

Demographics: (age, gender, etc)
Prevalence of shoulder complaints involves approximately 16 to 34 percent of the general population, with disorders of rotator cuff being the most common etiology of shoulder pain. Although shoulder pain occurs more in the elderly, with up to 50% by age 60, rotator cuff disorders can affect as early as age 40 []. This group of disorders is a major source of morbidity of among manual laborers and athletes whose work involving repetitive overhead motions [4,8,24].

Radiology: (separate CT, US, MR, angio if needed)
Magnetic resonance imaging (MRI), with T2 weighting such as a spin echo or fast-spin each (FSE) sequence being the most sensitive method, is a well-accepted diagnostic tool in the evaluation of shoulder pathology [3]. It is often difficult to distinguish tendinopathy from partial thickness tears, which typically manifest as a T1 low signal in conjunction with T2 or STIR high signal [15]. Although partial thickness and full thickness tears correspond more to high signals, no parameters have been established to reliably distinguish water and tendon signal. Furthermore, tendinopathy resulted from degenerative changes in the tendon have not been well distinguished from overuse injury on the MRI [29]. Intermediate signal intensity, though indicative of possible tear and/or tendinopathy, had even been reported in asymptomatic young individuals [29]. T2 weighted images of athletes with overuse injuries of the shoulder, likewise, were found to be lacking any inflammatory changes.

Other factors also contribute to the variability of tendon signal in rotator cuff disorders. Imaging artifacts called magic angle phenomenon that resemble pathology may be created as a result of the tendon orientations. As the supraspinatus tendon connects to the greater tuberosity via a curved course, the tendon becomes oriented to the bore of the magnet at 55 degrees and generates spuriously high signal due to loss of the rapid dephrasing [26]. This artifact may obscure pathology of the supraspinatus as it most frequently occurs at the same place as tears and tendinopathy. According to Wright et al., magic angle artifact was successfully overcome with a longer TE as water and tendon signals were more accurately distinguished.

Muscle interdigitation with tendon, especially pronounced with shoulder internally rotated, creates an artifact of intermediate signal on T1 and PD [15]. This artifact may be easily overcome with keeping the body in neutral position.

Despite significant strides made in improving sensitivity of detecting water signal, which reliably identify tears, intermediate signal remains even at longer TE (>37ms) [29]. Such findings may be complicated by underlying indolent conditions such as tendinopathy, which accounts for an increased baseline signal in the tendon. Although very long TE (>88ms) can be a highly sensitive tool in identifying tears, specific MRI findings for tendinopathy remain ambiguous and must be interpreted within clinical context [29].

Musculoskeletal ultrasound, another highly sensitive tool especially for assessing complete tears, is considered the gold standard in the initial evaluation of rotator cuff pathologies [1,14]. Unlike other imaging modalities, musculoskeletal ultrasound allows for comparison of the tendons of interest in motion to their counterparts on the contralateral side, making it much easier to correlate to physical exam findings. Although musculoskeletal ultrasound is limited by its inability to fully visualize the entire rotator cuff, ultrasound findings such as tendon hypoechogenicity, thickening with or without hypo or hyperechoic foci are characteristic of shoulder pathologies [1,18].

Plain shoulder films, due to low image resolution, are considered only useful for cases where complications including arthritis or calcification are involved on top of medical treatment failure, recurrent tendinopathy, or bony landmark identification prior to joint injection. As they are unable to reveal pathologies of rotator cuff tendinopathy, plain films are usually not indicated [25].

Differential Diagnosis: From a clinical perspective Cervical radiculopathy as might occur from disc herniation needs to be considered. Specific orthopedic tests for shoulder impingement and rotator cuff tear are used to help isolate the rotator cuff lesion. Cervical compression testing, motor strength, reflex changes and sensory alterations in the upper extremity can all contribute to the diagnosis of cervical radiculopathy. Often the two disorders can occur simultaneously. The patient always reserves the right to have more than one diagnosis. As such, advanced imaging offers a significant advantage in discerning the condition.

Prognosis and Treatment: (include survival statistics)
Approach to management of rotator cuff disorders depends on degree of severity of the injury, more specifically, whether it is a tear or just simply tendinopathy. As findings of tendinopathy must be corroborated in clinical context, a thorough clinical assessment is deterministic to the management approach. The examination must include a complete neck examination to rule out referred pain, inspection for rotator cuff atrophy, evaluation of range of motion, strength testing, and special tests such as Neer and Hawkins tests for impingement. Subacromial lidocaine injection may be applied to distinguish large tear from tendinopathy. With lidocaine, tendinopathy demonstrates return to normal muscle whereas muscle weakness remains in large cuff tears. If rotator cuff tears are strongly suspected, orthopedic referral is generally indicated [25].

Once rotator cuff tendinopathy is diagnosed, conservative medical therapy should be applied. Initial regimen usually consists of rest, ice, and NSAIDs. Cryotherapy, ice being the most, is effective in decreasing inflammation of the affected site while providing some analgesia [10]. NSAIDs, a first line medication for inflammation reduction, is usually given a short course for acute injuries. Its role in chronic therapy however remains unclear [10,20]. A number of physical therapy techniques have also been shown in several studies to be effective in facilitating rehabilitation of the rotator cuff muscles. Rehabilitation program generally consists of restoration of range of motion exercises, which helps loosen muscle stiffness while preventing adhesive capsulitis, then muscle strengthening and stretching as proven beneficial for short term and long term functioning, and lastly coordination to enhance integration of muscles [4,6,11]. Eccentric exercise that involves muscle contraction with application of a load during muscle lengthening has also been found to be effective [9]. Atheletes with increased load requirement are also recommended maintenance programs to meet their specific demands.

Subacute therapies, glucocorticoids and topical glyceryl trinitrate, are the 2nd line of treatment if no improvement is made with initial conservative management in 2-3 months. Although studies with proven benefits of steroid injection are controversial, glucocorticoids usually provide significant pain relief and is therefore a reasonable analgesic. Topical glyceryl trinitrate, vasodilates thereby bringing more blood flow to area of injury, was shown effective in symptom reduction in one randomize control study [20]. Glyceryl trinitrate is relatively contradindicated in patients with ischemic heart disease, anemia, those on phosphodiesterase inhibitor therapy, those with severity to nitrate, and closed-angle glaucoma despite its most common side effect being headache [17].

Orthopedic referral is the last resort and is only indicated in patients who fail medical therapy after 6-9 months and those with rotator cuff tears. Patients with complications such as refratory adhesive capsulitis from diminished use may also need surgical repair. Types of surgical interventions commonly performed include debridement, acromioplasty with debridement, and rotator cuff repair [10].