Shoulder joint pain
Disorders of the shoulder may affect the shoulder joint (glenohumeral joint), joints of the shoulder girdle (acromioclavicular and sternoclavicular joints) or the rotator cuff muscles and their tendons (supraspinatus, infraspinatus, subscapularis and teres minor).
Many shoulder conditions have an age and sex predilection . Instability is an important problem: primary anterior dislocation has an incidence of 12.3 per 100 000 per year and a lifetime prevalence of 2%. Epidemiology for other shoulder conditions is lacking as many conditions such as cuff tears may be asymptomatic. Cadaveric studies have shown a prevalence of up to 37 000 per 100 000 for partial thickness and 27 000 per 100 000 for full thickness cuff tears.
There are three potential locations for inflammation: the joints, the rotator cuff tendons and the bursae (particularly subacromial).
Degenerative arthritis of the shoulder joint may be primary or (more commonly) secondary to injury or disease. Cartilage wear, sclerosis (hardening of the bone), osteophyte formation and the development of bone cysts are characteristics of osteoarthritis, and a thickened contracted joint capsule leads to loss of function . Rotator cuff arthropathy follows massive cuff tear and leads to superior subluxation of the head with sclerosis of the acromion.The shoulder is affected in up to 90% of rheumatoid patients, with varying degrees of synovitis, erosion and destruction. If severe, there may be medial migration of the humeral head due to destruction of the glenoid .
Acute calcific tendinitis results in deposition of hydroxyapatite crystals in the supraspinatus tendon near its insertion on the greater tuberosity of the humerus . It is thought that the inflammation associated with the resorption of the deposit is responsible for causing the severe pain. There may also be inflammation of the tendon in relation to subacromial impingement. Recently the role of an hypoxic degenerate area near the cuff insertion has been recognized as a factor in the development of cuff tears. These tears may extend and retract causing weakness of the shoulder and rotator cuff arthropathy.
With impingement, the subacromial bursa can become thickened, inflamed and scarred. It has been recognized that the tip of the acromion is often more hooked and prominent in these patients, provoking impingement with abduction of the arm.
Anterior dislocation of the glenohumeral joint (98%) occurs following forced abduction, external rotation and extension of the shoulder . The anteroinferior capsule and labrum are usually torn off the glenoid, sometimes with a bony fragment (Bankart lesion). There is often an associated rotator cuff tear in middle age. Posterior dislocation is rare (2%) and is associated with epilepsy or electric shock. The forces that cause posterior dislocation often result in damage to the posterior capsule and labrum. Multidirectional instability is usually seen with generalized ligamentous laxity leading to redundant stretched inferior joint capsule. Dislocation may damage the surface of the humeral head and this increases the risk of future instability and arthritis.
Septic arthritis of the shoulder is rare and is more likely to occur in neonates, the elderly and immunosuppressed patients. Joint destruction and fibrosis can occur without prompt diagnosis and treatment. Sternoclavicular infection may spread to the mediastinum.
Osteomyelitis is also rare, but is most often seen in neonates. Infection can spread from the metaphysis across the growth plate (via vessels that can remain patent for 12 months) and cause damage to both this and the joint. This can result in partial or complete growth arrest as well as destruction of the joint.
Endocrine and metabolic disorders
Diabetes mellitus predisposes to neuropathic arthropathy (a destructive arthritis) probably due to a neuropathy. There is resorption, destruction and fragmentation of the humeral head with soft tissue calcification. This may be painless. Repetitive microtrauma (fragmentation) or hyperaemia (resorption) secondary to autonomic neuropathy may be the underlying cause. Other causes of autonomic neuropathy in the shoulder are syringomyelia and cervical spine injury. Patients with diabetes or thyroid disorders are predisposed to adhesive capsulitis (frozen shoulder), a disorder of unknown aetiology, characterized by contractile fibrosis and adhesions of the anterior capsule.
The shoulder is a common site for non-traumatic avascular necrosis. The majority (70%) of cases occur secondary to steroid use. Avascular necrosis is usually bilateral and can manifest as mild resolving necrosis, through to fracture and collapse of the humeral head and ultimately secondary arthritic change.
The unicameral bone cyst is the most common benign bone neoplasm (20%), of which 67% are located in the proximal humerus. These are fluid-filled cysts with thin sclerotic walls. Approximately 65% of these lesions will fracture and resolve by skeletal maturity, although spontaneous healing can occur. Other primary neoplasms are rare, but secondary metastatic deposits in the proximal humerus are common, often presenting as pathological fractures.
Scope of disease
The shoulder joint is important in positioning the hand about the body for function, working in tandem with the joints of the elbow and wrist. The shoulder girdle provides attachment for powerful muscles. The symptoms of shoulder disease can lead to loss of strength and movement, resulting in difficulties with daily activities such as washing and lifting.
True shoulder pain is usually experienced anterolaterally over the deltoid. The pain may be localized, diffuse or referred. Localized (point specific) pain usually occurs with trauma or rotator cuff damage. Diffuse pain is usually experienced with arthritis and bursitis. Shoulder pain may be referred down the arm (particularly with rotator cuff pathology). Acute onset of pain may be due to calcific tendinitis or shoulder injury. Precipitating factors are important, in particular the position of the arm (e.g. the painful arc in impingement syndrome).
It is important to remember that shoulder pain may be extrinsic, referred from the cervical spine, diaphragm or apex of the lung, or occur as a result of thoracic outlet syndrome and brachial neuritis.
Some loss of movement occurs with most shoulder disorders, but particularly with adhesive capsulitis.
Weakness at the shoulder joint may be muscular (rotator cuff tears) or neural (axillary, suprascapular nerve palsy and brachial neuritis).
With shoulder instability, patients may feel that their shoulder starts to dislocate in certain provocative positions, usually abduction and external rotation (anterior instability) or across the chest (posterior instability). Minimal trauma causing the first dislocation suggests pre-existing lax shoulder ligaments.
As with all upper limb problems, the dominant limb must be established. A detailed history is required to screen for a previous history of trauma and any coexistent disease (rheumatoid arthritis, diabetes). Occupation is important (overhead workers are predisposed to the symptoms of impingement or instability).
An orthopaedic examination is performed as follows:
The patient should be undressed to the waist. Inspection provides a lot of information. Surgical scars are usually anterior, and wasting of the deltoid is also best appreciated anteriorly. Wasting of the rotator cuff muscles is seen posteriorly. Swelling is unusual, but may be seen anteriorly with an inflamed bursa or arthritis. Medial migration of the rheumatoid shoulder and anterior dislocations cause a 'squared-shoulder' appearance with marked prominence of the acromion.
Warmth over the shoulder joint may be indicative of infection or inflammation. Tenderness over an arthritic glenohumeral joint is best elicited posteriorly. Tenderness beneath the anterolateral acromion occurs with impingement and cuff tears. Acromioclavicular joint pathology will cause localized tenderness over this joint.
Movement in both shoulders should be compared, both active and passive. Careful assessment will provide the diagnosis in a majority of cases. When assessing elevation of the arm, the scapula must be observed or palpated to determine its 'rhythm' (approximately one third of the movement should occur between the scapula and the thoracic wall). Crepitus with movement is common with an arthritic joint. If active and passive movements are equally reduced, particularly external rotation, then a diagnosis of frozen shoulder is likely. Greater passive than active motion is common with rotator cuff pathology and the arm will usually fall when released with a massive cuff tear ('drop sign'). A painful arc with active elevation (usually 60-120°) is the classic finding with impingement, and this pain can be eradicated by injecting the subacromial space with local anaesthetic. Strength of the rotator cuff muscles should be tested as weakness could signify a tear. Weakness from nerve palsy can be difficult to distinguish but suprascapular nerve palsy will leave subscapularis unaffected (internal rotation) and axillary nerve palsy will affect only deltoid (wasting) and often give numbness over the regimental badge area. Pseudoparalysis (reluctance to use the limb) may be the only clue to the diagnosis of septic arthritis in an infant.
These are mainly designed to diagnose instability. Apprehension can be induced by placing the shoulder in abduction and external rotation for anterior instability, and in flexion and adduction for posterior instability. The apprehension or discomfort can be reduced by pushing the humeral head posteriorly or anteriorly respectively, reducing the provoked subluxation. In multidirectional instability the shoulder will sublux inferiorly with traction on the arm (sulcus sign) and can usually be pushed both anteriorly and posteriorly with respect to the glenoid (drawer test). Generalized joint laxity should also be assessed as it is commonly found with multidirectional instability: hyperextension of elbows, knees and metacarpophalangeal joints of fingers, opposing the thumb to the ipsilateral forearm and placing palms of hands on the floor with knees extended.
The standard views are anterior-posterior (AP) and axillary. The AP view will demonstrate calcific deposits in the supraspinatus tendon and the pathological changes in arthritis (subchondral sclerosis, marginal osteophytes and cysts for osteoarthritis; periarticular osteoporosis, erosions and subluxation for rheumatoid arthritis). Superior head migration occurs with massive rotator cuff tear, and associated osteoarthritic changes affecting the acromion and superior head suggest cuff arthropathy . The axillary view can demonstrate subluxation or dislocation not appreciated on the AP view (particularly posterior dislocation) and may demonstrate a glenoid or tuberosity fracture.
Full blood count,erythrocyte sedimentation rate/C-reactive protein
Inflammatory markers and white cell count are usually raised in the presence of infection
Ultrasound of the shoulder
This is the first line of investigation in most units if a cuff tear is suspected. There is good sensitivity and specificity for full thickness tears but not for partial tears. Effusions and synovitis can also be identified. Ultrasound can be useful for accurate placement of injections in calcific tendinitis and can guide joint aspiration with suspected infection.
MRI of the shoulder
MRI is the first choice in suspected capsulolabral injury following a dislocation but has similar accuracy to ultrasound for cuff tears. MRI is the most accurate investigation for bone marrow abnormalities such as avascular necrosis.
Nerve conduction studies
Nerve conduction studies may be useful in cases of suspected axillary or suprascapular nerve palsy, or for distinguishing pain referred from the neck.
Many shoulder conditions will respond to a period of rest, and inflammatory problems may benefit from the application of heat or ice.
Standard analgesics including NSAIDs can prove useful for most painful shoulder conditions.
Targeted injections of steroid can improve symptoms of impingement, rheumatoid arthritis and adhesive capsulitis.
Physiotherapy is used in the treatment of frozen shoulder and can also help with impingement. It can help preserve motion and strength in the arthritic shoulder. Specific strengthening and proprioceptive retraining of the rotator cuff is the first line of treatment after dislocation.
Arthrodesis (shoulder fusion)
Arthrodesis is an uncommon operation but can still be of value as a salvage procedure following septic arthritis with joint destruction or severe cuff arthropathy
This involves replacement of the humeral head and often the glenoid . It is an option for patients with severe shoulder arthritis except those due to neuropathic or post-infective causes and those with massive cuff tears. Best results have been obtained in patients with osteoarthritis and low-grade rheumatoid arthritis, up to 95% reporting satisfactory or excellent results. The worst results occurred when treating advanced rheumatoid or cuff tear arthropathy, and in revision replacement surgery.
Once symptoms of pain are severe, shoulder replacement can be considered but whilst pain is relieved, restoration of range of movement is more unpredictable.
If general rheumatoid treatment is failing, surgical synovectomy of the shoulder joint and subacromial bursa can be performed. This should be done in early disease, and whilst good pain relief and functional improvement are seen, disease progression is not halted. Ultimately shoulder replacement is often required.
Extracorporeal shockwave therapy has been advocated by some to be beneficial for calcific tendinitis. 'Needling' the deposit and injecting local anaesthetic can also speed up recovery
Impingement and cuff tears
Following the general measures above, steroid injections can be beneficial when there is an element of inflammation (subacromial). Recalcitrant symptoms warrant surgical decompression and cuff repair. The former can be performed arthroscopically but the latter usually requires an open procedure. Decompression alone gives a 95% chance of relieving the pain of impingement. Small cuff tears require symptomatic treatment only. Larger tears warrant surgical repair but a re-rupture rate of up to 50% exists. If treated early (particularly in younger groups) satisfaction is usually high.
Following primary dislocation and reduction, an initial period of 3 weeks rest in a sling is followed by physiotherapy aimed at strengthening the rotator cuff and the scapular stabilizers (dynamic stability). There is a recurrence rate of up to 80% for anterior dislocation in patients less than 20 years. Patients in this group (in particular overhead athletes or workers) may require surgical stabilization. Repair of the torn capsule and labrum can be performed open (with up to 11% recurrence) or arthroscopically (up to 50% recurrence) with the latter preserving more external rotation. Posterior and multidirectional instability rarely require surgical intervention.
The natural history of this condition is of resolution but this can take over 3 years. Physiotherapy is the initial treatment and may be more effective following an injection of steroid to the shoulder joint. Manipulation of the joint under general anaesthetic can break the adhesions restricting movement. More recently there is a trend towards arthroscopic division of these adhesions, however there have been no randomized trials comparing this to the natural history of the condition.
Urgent washout of the joint is required. This may be performed arthroscopically and often needs repeating. Once a sample of fluid for culture is obtained, broad-spectrum intravenous antibiotics are commenced. These are converted to oral once clinical improvement is noted. Specific antibiotics are commenced following the culture report and a total course of 6 weeks is required.
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