Adhesive capsulitis of the shoulder

Adhesive capsulitis, also known as frozen shoulder, is a condition associated with shoulder pain and stiffness. It is a common shoulder ailment that is marked by pain and a loss of range of motion, particularly in external rotation. There is a loss of the ability to move the shoulder, both voluntarily and by others, in multiple directions. The shoulder itself, however, does not generally hurt significantly when touched. Muscle loss around the shoulder may also occur. Onset is gradual over weeks to months. Complications can include fracture of the humerus or biceps tendon rupture.

The cause in most cases is unknown. The condition can also occur after injury or surgery to the shoulder. Risk factors include diabetes and thyroid disease. The underlying mechanism involves inflammation and scarring. The diagnosis is generally based on a person's symptoms and a physical exam. The diagnosis may be supported by an MRI. Adhesive capsulitis has been linked to diabetes and hypothyroidism, according to research. Adhesive capsulitis was five times more common in diabetic patients than in the control group, according to a meta-analysis published in 2016.

The condition often resolves itself over time without intervention but this may take several years. While a number of treatments, such as NSAIDs, physical therapy, steroids, and injecting the shoulder at high pressure, may be tried, it is unclear what is best. Surgery may be suggested for those who do not get better after a few months. The prevalence of adhesive capsulitis is estimated at 2% to 5% of the general population. It is more common in people 40–60 years of age and in women.

Signs and symptoms
Symptoms include shoulder pain and limited range of motion although these symptoms are common in many shoulder conditions. An important symptom of adhesive capsulitis is the severity of stiffness that often makes it nearly impossible to carry out simple arm movements. Pain due to frozen shoulder is usually dull or aching and may be worse at night and with any motion.

The symptoms of primary frozen shoulder have been described as having three or four stages. Sometimes a prodromal stage is described that can be present up to three months prior to the shoulder freezing. During this stage people describe sharp pain at end ranges of motion, achy pain at rest, and sleep disturbances.
 * Stage one: The "freezing" or painful stage, which may last from six weeks to nine months, and in which the patient has a slow onset of pain. As the pain worsens, the shoulder loses motion.
 * Stage two: The "frozen" or adhesive stage is marked by a slow improvement in pain but the stiffness remains. This stage generally lasts from four to twelve months.
 * Stage three: The "thawing" or recovery, when shoulder motion slowly returns toward normal. This generally lasts from 5 to 26 months.

Physical exam findings include restricted range of motion in all planes of movement in both active and passive range of motion. This contrasts with conditions such as shoulder impingement syndrome or rotator cuff tendinitis in which the active range of motion is restricted but passive range of motion is normal. Some exam maneuvers of the shoulder may be impossible due to pain.

Causes
The causes of adhesive capsulitis are incompletely understood; however, there are several factors associated with higher risk. Risk factors for secondary adhesive capsulitis include injury or surgery leading to prolonged immobility. Risk factors for primary, or idiopathic adhesive capsulitis include many systemic diseases, such as diabetes mellitus, stroke, lung disease, connective tissue diseases, thyroid disease, heart disease, autoimmune disease, and Dupuytren's contracture. Both type 1 diabetes and type 2 diabetes are risk factors for the condition.

Primary
Primary adhesive capsulitis, also known as idiopathic adhesive capsulitis, occurs with no known trigger. It is more likely to develop in the non-dominant arm.

Secondary
Adhesive capsulitis is called secondary when it develops after an injury or surgery to the shoulder.

Pathophysiology
The underlying pathophysiology is incompletely understood, but is generally accepted to have both inflammatory and fibrotic components. The hardening of the shoulder joint capsule is central to the disease process. This is the result of scar tissue (adhesions) around the joint capsule. There also may be a reduction in synovial fluid, which normally helps the shoulder joint, a ball and socket joint, move by lubricating the gap between the humerus and the socket in the shoulder blade. In the painful stage (stage I), there is evidence of inflammatory cytokines in the joint fluid.

The main limiting factor in external rotation is due to the thickening of the coracohumeral ligament, which forms the roof of the rotator cuff and is a primary symptom of adhesive capsulitis. In addition, the coracohumeral ligament attributes to the limitation of internal rotation considering its connection to the supraspinatus and subscapular tendons. As the phases of adhesive capsulitis progress, the glenohumeral capsule begins to thicken and as a result the contraction of the capsule itself becomes the main reason as to why range of motion will be restricted in all planes of motion.

Diagnosis
Adhesive capsulitis can be diagnosed by history and physical exam. It is often a diagnosis of exclusion, as other causes of shoulder pain and stiffness must first be ruled out. On physical exam, adhesive capsulitis can be diagnosed if limits of the active range of motion are the same or similar to the limits to the passive range of motion. The movement that is most severely inhibited is external rotation of the shoulder.

Imaging studies are not required for diagnosis, but may be used to rule out other causes of pain. Radiographs will often be normal, but imaging features of adhesive capsulitis can be seen on ultrasound or non-contrast MRI. Ultrasound and MRI can help in diagnosis by assessing the coracohumeral ligament, with a width of greater than 3 mm being 60% sensitive and 95% specific for the diagnosis. Shoulders with adhesive capsulitis also characteristically fibrose and thicken at the axillary pouch and "rotator interval", best seen as a dark signal on T1 sequences with edema and inflammation on T2 sequences. A finding on ultrasound associated with adhesive capsulitis is hypoechoic material surrounding the long head of the biceps tendon at the rotator interval, reflecting fibrosis. In the painful stage, such hypoechoic material may demonstrate increased vascularity with Doppler ultrasound.

Grey-scale ultrasound can play a key role in timely diagnosis of adhesive capsulitis due to its high sensitivity and specificity. It is also widely available, convenient, and cost efficient. Thickening in the coracohumeral ligament, inferior capsule/ axillary recess capsule, and rotator interval abnormality, as well as restriction in range of motion in the shoulder can be detected using ultrasound. The range of motion is prohibited due to scapulohumeral rhythm changes occurring in the shoulder joint. The altered scapular kinematics can restrict anterior and posterior tilting, downward rotation and depression as well as external rotation. All of these restrictions lead the scapula to be excessively upwardly rotated. The restriction of the scapular posterior tilt is due to tightness in the lower serratus anterior, anterior capsule and the pectoralis minor. Downward rotation and depression are restricted due to the tightness of the rhomboids, upper trapezius and the superior capsule. Respective sensitivity values were 64.4, 82.1, 82.6, and 94.3, and respective specificity levels were 88.9, 95.7, 93.9, and 90.9.

Treatment
There is consensus that non-surgical management is the initial treatment of choice for frozen shoulder. There is no strong evidence to favor any particular approach; in fact, some reviews suggest that multi-modal approaches combining several treatments are better. Research in the UK showed that there were three typical approaches to treatment (physiotherapy, manipulation of the shoulder under general anaesthesia, and surgery (arthroscopic capsular release)). Alll three treatments were deemed effective but they had different benefits and drawbacks, suggesting clinicians and patients should decide together on the most appropriate treatment.

The effects of most treatments are primarily short-term, focusing on alleviating symptoms such as shoulder pain and reduced joint movement. Common treatments include exercise, physical therapy, oral analgesics such as paracetamol and NSAIDs, and intra-articular corticosteroid injections. Non-surgical treatment may continue for months, with more complex treatments such as ESWT, movement under analgesia, and hydrodilatation. It is unclear if these treatments lead to a quicker resolution of the disorder, or only manage chronic symptoms. The condition generally resolves itself with or without treatment. If conservative measures have no effect and the condition is long-lasting, or if evidence suggests surgical intervention, there are also several surgical procedures that may alleviate the disorder.

Medication
Medications such as NSAIDs can be used for pain control. Oral steroids may provide short-term benefits in range of movement and pain but have side effects such as hyperglycemia. Corticosteroids may also be used by local injection. In the short and medium term, intra-articular corticosteroid injections appear most effective in pain alleviation and increase in range of motion, although the injection does carry complications. Unfortunately, the effects of medication are not long-lasting. Oral corticosteroids in particular should not be used consistently to treat adhesive capsulitis, because of the dangers associated with long-term use and the lack of long-term benefit.

Exercise and physical therapy
Shoulder stretching and strengthening exercises improve shoulder function and decrease pain. When using intra-articular corticosteroid injections, the effects of exercise on short-term relief were not significant, although individual studies found some benefits. Concerning techniques, posterior glenohumeral mobilization had a large effect; mirror therapy, rotator cuff strengthening, spray & stretch, and end range mobilization had moderate results; continuous passive motion, scapular recognition, scapulothoracic exercises, yijin jing, and lower trapezius strengthening had small effects; and electromagnetic therapy, Kaltenborn mobilization, and instrument assisted soft tissue mobilization (IASTM) had insignificant effects compared to control kinesthetic exercises. It has been found that performing exercises under supervision is more effective than unsupervised exercise at home.

Extracorporeal shock wave therapy (ESWT) has been strongly recommended as a way of reducing pain levels and improving range of motion and functioning in people with Stage 2 and 3 adhesive capsulitis of the shoulder. Laser therapy was also found to have these similar effects for people dealing with Stage 2 adhesive capsulitis. Moderate evidence points to improvements in pain management, range of motion and functional status for interventions such as PNF techniques (stretching), continuous passive motion, dynamic scapular stability exercises, and conventional physiotherapy. Low evidence exists for manual muscle release.

Hydrodilatation or distension arthrography is controversial. However, some studies show that arthrographic distension may play a positive role in reducing pain and improve range of movement and function.

Manipulation of the shoulder under general anesthesia to break up the adhesions is sometimes used.

Surgery
If conservative measures are unsuccessful, surgery can be trialed. Surgery to cut the adhesions (capsular release) may be indicated in prolonged and severe cases; the procedure is usually performed by arthroscopy. Surgical evaluation of other problems with the shoulder, e.g., subacromial bursitis or rotator cuff tear, may be needed. Resistant adhesive capsulitis may respond to open release surgery. This technique allows the surgeon to find and correct the underlying cause of restricted shoulder movement such as contracture of coracohumeral ligament and rotator interval.

Prognosis
Most cases of adhesive capsulitis are self limiting, but may take 1 to 3 years to fully resolve. Pain and stiffness may not completely resolve in 20 to 50 per cent of affected people.

Epidemiology
Adhesive capsulitis newly affects approximately 0.75% to 5.0% percent of people a year. Rates are higher in people with diabetes (10–46%). Following breast surgery, some known complications include loss of shoulder range of motion (ROM) and reduced functional mobility in the involved arm. Occurrence is rare in children and people under 40, with the highest prevalence between 40 and 70 years of age. The condition is more common in women than in men (70% of patients are women aged 40–60). People with diabetes, stroke, lung disease, rheumatoid arthritis, or heart disease are at a higher risk for frozen shoulder. Symptoms in people with diabetes may be more protracted than in the non-diabetic population.