Flashcards in Orthopaedics - Shoulder Deck (31)
What causes shoulder instability?
Shoulder instability can be caused by an acute dislocation (of which anterior dislocations are most common). But instability can also be a problem without frank dislocation.
Causes of Instability can be considered under:
1) problems caused by an acute dislocation (e.g. rotator cuff tear)
2) structural defects that predipose to repeated dislocation
3) dislocation in the absence of a structural defect
What are the 4 rotator cuff muscles?
These are a group of muscles that form a hood around the proximal humerus and stabilise the glenohumeral joint. They are:
- supraspinatus - abducts in the plane of the scapula
- subscapularis - internally rotates the humerus
- infraspinatus - externally rotates the humerus
- teres minor - externally rotates the humerus when in abduction
What is the difference between a chronic and an acute rotator cuff tear?
A chronic rotator cuff tear may occur in the elderly without any history of trauma due to tendon degeneration. Chronic rotator cuff tears are problems of there own, and if partial are usually managed conservatively.
Acute cuff tears are the result of injury to a previously normal rotator cuff. They are common after dislocation in middle aged patients when they complain of weakness and pain.
How should an acute rotator cuff injury be managed?
X- rays should be performed to rule out a fracture followed by either an MRI or ultrasound to delineate the tendons of the rotator cuff.
Management is usually surgical for an acute cuff tear. Results of repair are better if performed within 3 months of the injury. This can be by open surgery or arthroscopically. Arthroscopic procedures have a quicker return to work rate but function is equal after 6 months for both approaches.
Is it possible to distinguish between a partial and a complete rotator cuff tear?
Yes. As well as being acute or chronic, rotator cuff tears can also be classified based on whether they are partial or complete.
In a partial tear, the intact tendon fibres allow vascular ingrowth and repair to occur. In a complete tear there is little or no reaction and no repair. Pain is abolished by injecting a local anaesthetic. If active abduction is now possible the tear must only be partial.
What are the 2 types of lesion that can cause recurrent dislocations?
When a shoulder is dislocated the glenoid or the head of the humerus can become damaged. This makes the shoulder joint unstable and it frequently dislocates even with minimal force.
2 lesions in particular are associated with a previous dislocation that causes shoulder joint instability and predisposes to further dislocations. These are the Bankart lesion and the Hills-Sachs lesion.
What is a Bankart lesion? How is it investigated?
A dislocation can tear off the cartilagenous labrum (lip of the glenoid fossa). This is known as a Bankart lesion.
If this is associated with a chip off the rim of the glenoid it is called a bony Bankart lesion. Both can be associated with recurrent dislocations.
Investigations include a CT to evaluate bone loss and an MRI arthrogram, where contrast is injected into the shoulder joint before an MRI is performed. Contrast can be seen leaking out of the shoulder through a tear in the labrum.
How is a Bankart lesion repaired?
Both Bankart and bony-Bankart lesions require repair due to the increased risk of future dislocation. They can both be repaired arthroscopically but if there is a very large bony-Bankart then an open approach is more appropriate. There are a number of operations to address a large bone loss of the glenoid, one is a Bristow-Latarjet procedure. Here the tip of the coracoid process and the conjoint tendon is removed and screwed into the front of the glenoid. This extra bit of bone builds up the front of the glenoid and prevents future anterior dislocations.
What is a Hill-Sachs lesion?
Sometimes the head of the humerus can be damaged in a dislocation. Because the humeral head is relatively soft, an anterior dislocation can lead to the bony glenoid forming a divot in the head. This is called a Hill-Sachs lesion.
As the shoulder is brought into external rotation, the glenoid "falls into" the bony defect in the head of the humerus. When this happens it is called an "engaging Hill-Sachs lesion".
Treatment is surgical. Both the joint capsule and ligaments are pinned into the defect using a bone anchor. The result is to fill the defect and limit external rotation.
Why does hypermobility cause shoulder instability?
Hypermobility is a common cause of shoulder problems in younger patients. It causes dislocations in the absence of any structural defect.
The most common form is generalised hypermobility syndrome. It is most common in adolescent girls and may be due to the effects of hormones on soft tissue. The prognosis is good though. Patients tend to grow out of this and it is rarely a problem in adulthood. The main treatment modality is physiotherapy.
How is hypermobility diagnosed?
Hypermobility is diagnosed using the Beighton scoring system. This gives points for:
- hands flat on the floor (1 point)
- elbow hyperextension (2 points)
- knee hyperextension (2 points)
- thumb touches the forearm (2 points)
- little finger MCP hyperextension past 90 degrees (2 points)
Score is out of 9. >4 is abnormal.
What causes an anterior dislocation?
Dislocation causes shoulder instability.
Anterior dislocation of the shoulder is the most common. It usually follows an acute injury in which the arm is forced into abduction, external rotation and extension - i.e. throwing an object
The typical patient is a young man who complains of the shoulder repeatedly "going out of joint" during over-arm movements, and each time having to have it manipulated back into position.
What causes a posterior dislocation?
Posterior dislocation is rare; when it occurs it is usually due to a violent jerk in an unusual position - i.e. following an epileptic fit or a severe electric shock (lightning strike). Recurrent posterior instability is nearly always a subluxation, with the humeral head riding back on the posterior lip of the glenoid.
How does subluxation typically present?
It is important to remember that subluxation is a partial dislocation. Its presentation is less obvious. The patient may describe a "catching" sensation (rather than complete dislocation) followed by "numbness" or weakness.
What type of joint is the shoulder joint? What type of cartilage is present?
The shoulder joint is a ball and socket joint that permits movement in multiple planes (i.e. abduction, adduction, extension, flexion, internal and external rotation).
It is formed by the proximal head of the humerus articulating with the shallow glenoid fossa of the scapula. The glenoid is deepened by a fibrocartilagenous ring called the glenoid labrum.
Both articular surfaces are lined with hyaline cartilage.
What are the attachments of the shoulder joint capsule?
The shoulder joint capsule is quite lax and permits a wide range of movements. It is attached medially to the margins of the glenoid, and laterally to the anatomical neck of the humerus except inferiorly where it extends to the surgical neck.
The capsule is strengthened by slips of tendon from the rotator cuff muscles.
Where is the synovial membrane in the shoulder joint?
The synovial membrane secretes synovial fluid. It lines the joint capsule and covers the articular surfaces. It surrounds the intracapsular portion of the tendon of the long head of biceps and extends beyond the transverse humeral ligament as a sheath.
It forms one of the 2 bursae within the shoulder joint - the subscapular bursa anteriorly by protruding through the anterior wall of the capsule.
What are the clinical syndromes affecting the rotator cuff muscles?
Rotator cuff lesions present as 5 more or less distinct clinical syndromes:
1) acute tendinitis
2) chronic tendinitis (impingement syndrome)
3) tears of the rotator cuff
4) adhesive capsulitis (frozen shoulder)
5) biceps tendon lesions
What is acute tendinitis? How does it present?
This is where deposits of calcium hydrozyapetite appear in the supraspinatus tendon. Calcification alone is probably not painful. Symptoms are due to the vascular reaction which produces swelling and tension in the tendon.
Clinically, a young adult complains of aching sometimes following over use. Hourly the pain increases in severity rising to a climax. After a few days the pain subsides and the shoulder gradually returns to normal.
What imaging and treatment are needed in acute calcific tendinitis?
On x ray, calcification just above the greater tuberosity is always present. As pain subsides, the calcification is resorbed or dispersed into the subdeltoid bursa.
1) conservative - if symptoms are not severe the arm is rested in a sling and a short course of NSAIDs is given. If pain is more intense a single injection of corticosteroids and local anaesthetic is given to the most painful area
2) surgical removal of calcific material if pain is not relieved conservatively
Define impingement syndrome?
Impingement syndrome is also called chronic tendinitis. Over use or microtrauma of the rotator cuff may cause a subacute or chronic vascular response in the tendon. Impingement of the rotator cuff against the coracoacromial arch during abduction may play a part in the process.
Osteophyte formation on the under-surface of the acromioclavicular joint may also play a role.
How does impingement syndrome present?
The patient usually aged 40-60 complains of pain in the shoulder and over the deltoid muscle. It is worse at night. The shoulder looks normal but is tender just below the anterior edge of the acromion process. In long standing cases, there may be wasting of the muscles and loss of power.
What findings on examination suggest impingement syndrome
There are 3 examination findings to suggest impingement:
1) Painful arc - the patient experiences pain on active and passive abduction. Pain starts around 60 degrees and continues to 120. After this the pain stops
2) Neer's test/sign - this is a purely passive test. The patients arm is internally rotated and passively extended in line with the scapula. They experience the same symptoms as a painful arc
3) Hawkin's test - the shoulder is abducted and internally rotated at different degrees. Pain on different degrees of internal rotation is a positive test.
NB - scarf test is NOT a test for impingement but is ofte performed alongside the other impingement special tests. The scarf test is for ACJ pathology.
What is the management of impingement syndrome?
1) conservative - rest, physio and NSAIDS followed by steroid and local anaesthetic injections
2) surgery can be considered if symptoms keep recurring. The rotator cuff is "decompressed" by excising the coracoacromial ligament and the antero-inferior part f the acromion. If osteophytes are present then they are also removed
Most surgical procedures are performed arthroscopically.
What are the long term complications of impingement syndromes?
The absence of the stabilising effect of the rotator cuff may lead to the humeral head gradually subluxing upwards. This causes joint instability and osteoarthritis may occur.
What is a frozen shoulder?
A frozen shoulder, or adhesive capsulitis, is a term that should be reserved for a well defined disorder of progressive pain and stiffness that usually resolves spontaneously after about 18 months. The cause is uncertain.
(Think 666 - 6 months pain, 6 month plataeu, 6 month improvement)
Clinically, a patient aged between 40-60 gives a history of trauma (usually trivial) followed by pain. Gradually the pain increases in severity and often prevents them from sleeping on the affected side. After several months it gets better and as it does the stiffness gets worse. Usually there is nothing to see except slight wasting.
1) post-traumatic stiffness
2) disuse stiffness
3) regional pain syndrome
How is frozen shoulder treated?
1) conservative - injection + physiotherapy + analgesia
Once the acute pain has subsided manipulation under anaesthtesia (MUA) can improve recovery
2) surgical - involves arthroscopic division of the interval between supraspinatus and infraspnatus may increase range o movement
What are the features of OA in the shoulder joint?
Shoulder OA is usually secondary to other disorders - e.g. congenital dysplasia, local trauma, long standing rotator cuff lesions, RA or avascular necrosis of the humeral head
Patients are usually elderly (>50) and present with pain an stiffness.
What are the x ray features of shoulder OA?
- Loss of joint space
- Subchrondral sclerosis
- subchrondral cysts