Shoulder is the most mobile joint in human body having the widest range of movements. However, the free mobility comes at a cost of instability. And hence, shoulder is also the most common joint to get dislocated. Let’s have an overlook at various aspects of a shoulder dislocation.
What is a dislocation?
A joint is formed by the ends of two bones. ’Dislocation’ is when one of the two bones forming a joint gets completely displaced from its anatomical position. When there is only partial displacement, its called a ‘subluxation’.
What does exactly happen in a shoulder dislocation?
Shoulder is a ‘ball & socket’ type of joint formed by ball of the arm bone (humerus) and the socket (glenoid) of the shoulder blade (scapula). But the socket is not deep enough to keep the ball in place. Various structures help in keeping the joint stable during movements.
The socket is lined by ‘labrum’, a rim (boundary) of fibrocartilage, which is also the anchor point for the joint capsule (envelope). This is one of the most crucial but weak points of the joint.
When shoulder dislocates the first time, it tears the labrum off the socket bone. The name given to this tear is ‘Bankart lesion’. Even after the joint is reduced back in its position, the labrum does not heal well and acts as a weak point for repeated episodes of dislocation. Also, torn labrum can rarely take a small piece of bone away from the socket known as ‘Bony Bankart lesion’. During dislocation, the ball (head of humerus) gets impacted against the sharp edge of the socket and that forms a depression on the ball called ‘Hill-Sachs lesion’.
How to understand if someone has suffered a shoulder dislocation?
Shoulder dislocation happens for the first time after a significant trauma such as road traffic accident, fall from height, high velocity trauma while playing contact sports. The successive episodes of dislocation may occur without significant injury. In recurrent dislocations, it can even happen during sleep.
Symptoms of dislocation are:
- Sudden onset unbearable shoulder pain immediately after the injury
- Inability to move the arm at allSquaring or flattening of the round contour of shoulder
- Numbness or tingling in the arm
What are various types of shoulder dislocation?
There are three main types
1. Anterior: The ball (head of the humerus) gets displaced forward, in front of the socket (glenoid).
- Most common type amounting to around 96% of all shoulder dislocations.
- Typically results from fall on an outstretched hand or a direct blow in throwing position.
- Can be easily diagnosed by clinical findings and a radiograph (X-ray).
2. Posterior: The ball moves backwards, behind the socket
- Less common (3%),
- often caused by seizures, electrocution
- Can be missed out on standard X-rays if not looked for carefully
3. Inferior (luxatio erecta): The rarest type (<1%)The ball moves downwards, below the socket. Results from extreme force that pulls the arm upwards. Dislocation is obvious on X-ray.
Why does a shoulder dislocation happen?
Various risk factors can play a role.
1) Trauma:
- Falls onto an outstretched hand
- Sports injuries (especially contact sports like football or rugby).
- Throwing position (arm abducted & externally rotated) is most prone to get an anterior dislocation. Road traffic accidents
2) Congenital Conditions:
Some individuals have excessively loose ligaments since birth known as ‘generalised ligamentous laxity’, increasing the risk of dislocation even without significant trauma. This could be physiological or part of a syndrome such as Ehler-Danlos Syndrome.
3) Age and Gender:
Young boys below the age of 25 years are most commonly affected due to higher activity levels and participation in competitive sports.Dislocations in older age group are a different entity and are associated with rotator cuff tendon tear.
What happens if it is not treated in time? What is a ‘Recurrent Dislocation’ ?
When the same shoulder dislocates 3 or more times, it is called a ‘recurrent dislocation’. With every successive episode of dislocation, the labrum quality gets deteriorated and bone of the ball & socket starts to get eroded.
As the bone loss of the socket increases, the ball starts dislocating easily even without a significant trauma or fall. Patients tend to dislocate shoulder even during sleep as the muscles around the shoulder are relaxed.
How is a dislocation and recurrent instability diagnosed?
It is always a combination of clinical and radiological modalities.
A) Physical Examination:
- Identifying a dislocated shoulder is quite straight forward.
- Acute onset severe pain, inability to move shoulder at all, arm by the side of the body supported by other hand and squaring of round shoulder contour is characteristic of a dislocation.
- Neuro-vascular assessment is essential to check for axillary nerve or blood vessel injury.
- In case of a recurrent instability, certain special clinical tests like Apprehension test, Sulcus sign, Load and shift test help in making a diagnosis.
- Generalised ligamentous laxity should be evaluated in every patient using Beighton score.
B) Radiology:
X-rays are the go investigation in acute dislocation episode. They confirm the type and direction of dislocation and rule out associated fractures. Bony Bankart and Hill-Sach lesion can be seen on special X-ray views.
MRI is the gold standard to diagnose the labral injury (Bankart lesion).
In case of recurrent dislocations, CT scan is a must to detect the extent of bone loss and decide on definitive management.
What is the treatment for an acute shoulder dislocation?
First and foremost thing is to reduce the dislocated joint. Method of reduction depends on the type of dislocation and associated fractures. Most commonly followed treatment protocol is:
1. Closed Reduction: Orthopaedic surgeon gently manoeuvres the ball back into the socket.It is usually done under an analgesic injection. Rarely if the patient is apprehensive and non-compliant, short general anaesthesia may be required.Pain relief is immediate once the joint is back in place. Any kind of forceful reduction method should be avoided as it can lead to a fracture.
2. Immobilisation: After reduction, the shoulder is often immobilised in a shoulder immobiliser sling for 3 weeks.
3. Physical Therapy: Intermittent elbow and wrist movements are encouraged throughout the period of immobilisation. After 3 weeks, gradual exercises are started to regain the complete range of shoulder movements. This is followed by strengthening of the muscles around shoulder joint. Return to contact sports, heavy activities need to be avoided for at least 3 months.
4. Surgical Treatment: This is rarely required in an acute episode in following conditions:Inability to reduce the joint even under general anaesthesiaAssociated displaced fracture of ball (needs fixation either by anchors or plate-screwsAssociated bony lesion of the socket (Bony Bankart)The treatment after a single episode of shoulder dislocation is essentially conservative. Only when there are recurrent dislocations happening, a definitive surgical management is required.
What is the treatment of recurrent shoulder dislocation?
Surgery is required in order to restore the anatomy. Indications and choice of surgical procedure depend on multiple factors like severity of bone loss of the socket, dimensions of Hill-Sachs lesion, patient’s age, occupation, hand dominance, involvement in sports or heavy labour activities and functional demands.
Common surgical procedures include:
Bankart repair: torn labrum is repaired (arthroscopic) when the bone loss is <15%
Remplissage: infraspinatus tendon is fixed into the Hill-Sach defect on the ball (arthroscopic) when the lesion is off-track
Bone block cerclage: bone loss of the socket is restored with a bone graft (arthroscopic) when the glenoid bone loss is sub-critical (15-20%)
Latarjet procedure: coracoid process is cut and attached in front of the socket with screws when the socket bone loss is critical i.e. >20% (open / arthroscopic)
What is the recovery timeline after a surgery?
Complete recovery requires strict adherence to supervised rehabilitation exercises and a gradual return to activity. Typically shoulder is immobilised in arm sling support for 2-3 weeks post surgery. Although there are different protocols after different surgeries, patient is expected to regain complete range of movements by 3 months and considerable strength by 6-9 months. Return to competitive sports or heavy activities can be resumed at one year based on the recovery.
How to prevent a shoulder dislocation or re-dislocation?
Following measures would be useful:
1. Strengthening of scapula and shoulder muscles
2. Maintain flexibility. Follow stretching routine before workouts or sports.
3. Avoid overhead or throwing activities if the shoulder is prone to dislocation
4. Following proper techniques and using protective gears4. Avoid a re-injury: Return to sports only when fully recovered. Gradually increase activity levels under proper guidance.
5. Consult an orthopaedic surgeon immediately when the first episode of dislocation occurs.
Takeaways..
Shoulder dislocation is a serious injury that should not be ignored. While it is common; prompt medical attention, expert treatment, and a structured rehabilitation can ensure full recovery and reduce the risk of recurrence. Remember that every episode of dislocation will cause more & more damage to your shoulder!