Adhesive capsulitis of the shoulder

Adhesive capsulitis of the shoulder, also known as frozen shoulder, is a self-limiting painful condition characterized by restricted active and passive range of motion of the shoulder lasting for more than one month and unremarkable shoulder X-ray findings ^23,34. Adhesive capsulitis can rarely affect other sites, such as the ankle ⁸.

Epidemiology

The incidence in the general population is thought to be 3-5%. Adhesive capsulitis typically affects women in their 5^th to 6^th decades, although patients with co-morbidities such as diabetes mellitus may develop the condition at earlier ages. The incidence in patients with diabetes is reported to be 2-4x higher than in the general population.

Recent studies seem to demonstrate how adhesive capsulitis can represent a rare potential complication resulting from improper administration of the COVID-19 vaccine ^27,28 .

Diagnosis

Adhesive capsulitis is principally a clinical diagnosis with no definitive diagnostic criteria. Diagnostic criteria used in some research papers (c. 2023) ^25,26 include the presence of at least 4 of the 5 following criteria

• shoulder pain

• <90 degrees anterior flexion

• <90 degrees abduction

• <50% external rotation compared to the contralateral shoulder

• <50% internal rotation compared to the contralateral shoulder

in patients without prior shoulder surgery, trauma, synovitis, rotator cuff or labral injury, calcific tendinosis, or rheumatoid or septic arthritis.

Clinical presentation

The characteristic symptoms are shoulder pain and reduced active and passive shoulder range of motion ^23,24. The pain also occurs at night, which negatively affects sleep quality ²².

Adhesive capsulitis presentation can be broken into three distinct stages:

• freezing: painful stage 

  • patients may not present during this stage because they think that eventually, the pain will resolve if self-treated

  • as the symptoms progress, pain worsens, and both active and passive range of motion (ROM) becomes more restricted

  • this can eventually result in the patient seeking medical consultation

  • typically lasts between 3 and 9 months and is characterized by acute synovitis of the glenohumeral joint

• frozen: transitional stage

  • most patients will progress to the second stage

  • during this stage, shoulder pain does not necessarily worsen

  • because of pain at the end of the range of motion, arm movement may be limited, causing muscular disuse

  • can last between 4 to 12 months

  • the common capsular pattern of limitation has historically been described as diminishing motions with external shoulder rotation being the most limited, followed closely by shoulder flexion, and internal rotation

  • a point is eventually reached in the frozen stage where pain does not occur at the end of the range of motion

• thawing stage

  • begins when the range of motion starts to improve

  • lasts anywhere from 12 to 42 months and is defined by a gradual return of shoulder mobility

Pathology

Adhesive capsulitis is divided into two main types: 

• primary or idiopathic

  • absence of preceding trauma

• secondary 

  • major or minor repetitive trauma

  • shoulder or thoracic surgery

  • endocrine, e.g. diabetes, hyperthyroidism ¹²

  • rheumatological conditions

Radiographic features

Fluoroscopy

Described features of fluoroscopic arthrography include ^ref:

• limited injectable fluid capacity of the glenohumeral joint 

• small dependent axillary fold

• small subscapularis bursa

• irregularity of the anterior capsular insertion at the anatomic neck of the humerus

• lymphatic filling may be present

Ultrasound

• limitation of movement of the supraspinatus tendon is considered a sensitive feature ⁷

• limited external rotation, identified when positioning for subscapularis tendon assessment

• thickened coracohumeral ligament (CHL) can be suggestive ⁹

• thickening of the inferior glenohumeral capsule ¹⁶

• hypoechoic soft tissue and/or increased vascularity around the long head of the biceps (LHB) tendon at the rotator interval ^13,20

MRI/MR arthrography

MRI is often used to confirm the clinical diagnosis of adhesive capsulitis and exclude other shoulder conditions ²⁵. The signs of adhesive capsulitis are variable with some but rarely all of the following expected to be present:

• increased signal intensity of the inferior glenohumeral ligament on T2FS or PDFS sequences ^17,19,25

• coracohumeral ligament thickening ≥3-7 mm ^4,19,25

• subcoracoid triangle sign ⁴

• joint capsule thickening ²

  • anterior capsule thickness >3.5 mm and abnormal hyperintensity ¹⁴

  • axillary pouch thickening >3-4 mm has been specific for adhesive capsulitis in some studies ^1,2,5,25 but not in others ^3,4,17-19

• abnormal soft tissue thickening (>3-7 mm ²⁵) within the rotator interval with signal alteration ¹⁸

• abnormal soft tissue encasing the biceps anchor ¹⁸

• variable capsular and synovial enhancement within the axillary recess and rotator interval ¹⁸

• distention of the subscapular recess is very suggestive ²¹

• contrast-enhancement of the inferior glenohumeral ligament and rotator interval has been shown to have a sensitivity and specificity of >90% for frozen shoulder, however, contrast administration does not significantly increase the diagnostic performance over non-contrast 3 T MRI ²⁵

Chronic frozen shoulder may show low T2 signal and pericapsular scarring ¹⁵. 

Treatment and prognosis

Adhesive capsulitis is typically a self-limiting disease that improves over 1-2 years. Conservative treatment with physiology and NSAIDs is currently preferred as first-line treatment ²⁵. For patients with refractory symptoms more invasive treatment options include ²⁵:

• corticosteroid injections, e.g. subacromial bursal injection, intra-articular glenohumeral injection

• glenohumeral hydrodilatation

• closed manipulation under anesthesia

• arthroscopic glenohumeral arthrolysis

• trans-arterial embolization