Anterior instability means the shoulder is unstable towards the front of the joint. Traumatic anterior dislocation is the most common form of shoulder instability. It is seen most often in young men, but it can affect anyone who sustains a high-energy traumatic injury to the shoulder.
In a traumatic anterior dislocation the ball of the upper arm bone is levered forward out of its socket. Because the joint is held forward by soft tissue structures that are torn in the process, the shoulder usually cannot be put back without assistance. Reduction, putting the ball back into the joint, is normally carried out under anaesthetic in a hospital emergency department.
The pain of the dislocation itself settles over the following days, and most people regain reasonable movement. The difficulty is what happens afterwards: the structures that tore during the dislocation do not reliably heal back where they belong, which leaves the shoulder at risk of coming out again.
Symptoms
- A shoulder that comes fully out of joint after an injury, with severe pain and an inability to move the arm, needing reduction in hospital.
- Further episodes of the shoulder coming out, often with progressively less force each time.
- Subluxation, where the shoulder slips partly out of position and goes back by itself.
- Apprehension, a strong sense that the shoulder is about to come out, with the arm raised out to the side and rotated backwards. This is often the position of a throw or a tackle.
- Pain, weakness and loss of confidence in the arm between episodes, with avoidance of sport, overhead activity and certain sleeping positions.
Causes
The initial event is an injury. A force applied to the arm when it is out to the side and rotated backwards pushes the ball of the shoulder forward until it comes out of the socket. In doing so it tears the structures that normally stop that movement.
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Labral tear. The labrum is the rim of cartilage around the edge of the socket, and the front of the labrum is torn in approximately 95% of anterior dislocations. It is this tear that allows the shoulder to dislocate.
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Capsular injury. In some cases the joint capsule tears away from the upper arm bone rather than from the socket. This is known as a HAGL lesion, and it is important to identify because it is repaired differently.
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Rotator cuff tear. Tearing of the rotator cuff tendons during a dislocation occurs only rarely, but it is more likely in older patients.
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Bone injury. Repeated dislocations can wear bone away from the front rim of the socket and create a dent in the back of the ball of the shoulder. Significant bone loss makes the joint less stable and changes which operation is appropriate.
Risk of further dislocation
The risk of the shoulder dislocating again depends mainly on two things: the age at the time of the first dislocation, and how active the person remains afterwards. A younger age at first dislocation and a higher level of activity both increase the risk.
Published series report that patients who dislocate under the age of 19 and remain active have a risk of further dislocation of approximately 90%, that the risk in those who dislocate under the age of 15 approaches 100%, and that the risk falls with increasing age, to in the order of 33% at around the age of 40. Individual results vary, and your own risk is best estimated after assessment.
Diagnosis
The diagnosis of a dislocation is usually clear from the history and from X-rays taken in the emergency department, which confirm the direction of the dislocation and show whether there has been an associated fracture.
Once the shoulder has been reduced, an MRI scan is normally arranged, because it shows which of the soft tissue structures have torn, in particular the labrum, the capsule and the rotator cuff tendons. A CT scan is sometimes added to assess bone loss from the rim of the socket, as this influences the choice of procedure.
Treatment
Non-surgical treatment
Immediately after reduction, a sling is usually recommended for the first few days, until the pain settles. Movement is then restored gradually.
Physiotherapy aids recovery of movement, strength and control of the shoulder blade, and is worthwhile for that reason. However, there is no good evidence that a rehabilitation programme substantially reduces the likelihood of the shoulder dislocating again, because it cannot restore the torn labrum and capsule to their correct position.
Non-surgical management is more often appropriate in older patients, in whom the recurrence risk is considerably lower, and in those whose activities do not place the shoulder in provocative positions.
Surgical treatment
For younger, active patients, treatment of traumatic anterior instability is essentially surgical. The aim of surgery is to repair the structures that were torn during the dislocation and so restore the normal restraints to the joint. It is usually performed arthroscopically, through keyhole incisions.
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Arthroscopic Bankart repair. The torn labrum is reattached to the rim of the socket with anchors and the capsule is tightened. This is used where there is a labral tear without significant bone loss.
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Latarjet and labral repair. A block of bone from the coracoid is transferred to the front of the socket to replace bone that has been lost, with repair of the labrum at the same time.
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Remplissage. A defect in the back of the ball of the shoulder is filled so that it cannot engage on the front rim of the socket.
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Stabilisation. General information about stabilisation surgery and recovery.
Which procedure is suitable depends on what the imaging shows, how many times the shoulder has dislocated, and what activities you want to return to. Any procedure carries risk, including the risks of general anaesthetic, a small risk of infection, a small risk of nerve injury, stiffness, and the possibility of the shoulder becoming unstable again. These risks are discussed in consultation.
What to do next
If your shoulder has dislocated, an assessment with imaging will show what has been injured and allow the risk of further dislocation to be discussed in your own circumstances. Background on the joint itself is on the shoulder anatomy page, the wider picture is on the shoulder instability page, and recovery after surgery is covered under rehabilitation.
To arrange an assessment, see consultation. The consultation FAQs explain what to bring, the surgery FAQs cover common questions about having an operation, and accommodation has information for patients travelling to Brisbane.
This page is general information and is not a diagnosis. Individual circumstances vary, and the right treatment for you can only be determined after assessment. Any procedure carries risk; these are discussed in consultation.
