Shoulder Instability

The notes on this page are written as a source of information to both patients and health professionals. It is a general overview and its content should not be seen as direct medical advice. Further information regarding diagnosis and treatment specific to your condition can be made via a consultation with Dr Amaranath.

Shoulder Anatomy

The shoulder joint is a ball and socket joint consisting of the head of the humerus (ball) and the glenoid (socket). The joint itself is shallow in nature which allows it to be mobile and achieve a near full 360° range of motion. It is surrounded by soft tissue structures such capsule, ligaments (thickening of the capsule), tendons and muscles. Each play a role in providing stability and movement to the shoulder through different daily activities. The labrum and ligaments are the key structures critical to its stability.

What is shoulder instability?

The shoulder joint is an inherently unstable joint due to its anatomy. However, this potential negative also allows it to have the greatest range of motion. The shoulder’s primary stabilisers include the glenohumeral ligaments, labrum, articular congruity (shape of joint surface) and version (which way the glenoid faces). When any of these structures are affected either traumatically or genetically, then the joint can become unstable. Commonly that instability occurs with the shoulder dislocating anteriorly (front), but in rare cases it can also dislocated or sublux posteriorly.

Anterior dislocations often occur after trauma and the patient can have symptoms of joint instability and apprehension to certain shoulder positions. While posterior dislocations present with more repetitive use or atraumatically and have symptoms of pain in the posterior shoulder. 

What are the common causes?

  1. Traumatic – This occurs following a direct impact to the shoulder and can drive the shoulder in either an anterior or posterior direction causing the humeral head to dislocate in relation to the glenoid cavity.

  2. Micro-traumatic – This is where repetitive trauma to the structures of the glenoid can lead to loss of stability and subluxation of the humeral head. Commonly it is seen in posterior subluxation of the humeral head due to sports such as swimming, tennis and throwing.

  3. Atraumatic – This occurs when the shoulder dislocates or subluxes in either an anterior or posterior direction due to patient related factors. This can include global ligamentous laxity and excessive glenoid retroversion (posterior instability).

What are the preferred Investigations/Imaging?

  1. Plain X-Ray of the shoulder - This should include an Anterior/Posterior, Lateral and Axillary view.

  2. CT scan of the shoulder - This is commonly used to asses any bony injury to the humeral head or glenoid. In some instances, Dr Amaranath will ask for a specific 3D reconstructed image of the glenoid with humerus subtraction to calculate the glenoid track. This will help guide surgical treatment if required.

  3. MRI Shoulder – This helps to identify any injury to the glenoid labrum, ligaments and associated rotator cuff, which will help guide the management plan.

What are the treatment options? 

  1. Non-operative – Once a diagnosis has been obtained commonly the first line of treatment would include non-operative measures such as analgesia, extensive physiotherapy and activity modification. This will have to be tailored to the injury pattern and functional requirements of the patient.

  2. Arthroscopic Labral Repair/Stabilisation– In cases where non-operative measures have failed or there is an unstable labral tear or ligamentous injury, then arthroscopic shoulder stabilisation is recommended. This involves key hole surgery and repair of the torn labrum and capsule with the use of small anchors that fix the labrum back to its origin.

  3. Latarjet Procedure (Anterior Bone Block) – This surgical procedure involves moving the coracoid (bony prominence in the front of the shoulder where the conjoint tendon attaches) to the front of the glenoid. This increases the stability of the shoulder by reinforcing the ligaments in positions of dislocation, increasing the glenoid surface area and tightening the capsule. The latarjet is used in patients that fail the arthroscopic repair or who have significant bone loss of the glenoid due to trauma.

What does the rehabilitation/recovery involve?

To find out more about rehabilitation and recovery after shoulder surgery please see our Rehabilitation Protocols here.