Shoulder Instability / Dislocation
Anatomy And Pathology
The Shoulder is the most commonly dislocated major joint in the human body.
This is due to the design of this ball (humeral head) and socket (glenoid) joint – the most mobile joint in the body. The glenoid is very shallow to allow a great degree of mobility.
When the shoulder dislocates due to sports or accidents the primary lesion is a traumatic detachment of the structures from the front of the glenoid. This is often termed a "Bankart" lesion.
These anterior structures are made up of
- The Anterior Inferior Glenohumeral Ligament (AIGHL) - The AIGHL is a thickening in the joint capsule.
- The Labrum is a bumper at the edge of the socket to increase the depth of the socket it is here the AIGHL attaches.
These 2 structures are responsible for preventing the ball (humeral head) from slipping out of glenoid. When torn away from their origin they are damaged and stretched and have very poor ability to heal in the correct position.
Associated with the above damage - 2 other very important things can occur
- A fracture of the bony socket / glenoid (Bony Bankart)
- A divot in the back of the ball part of the shoulder (Hill Sachs Lesion)
These additional injuries dictate the requirement for different surgical approachs to deal with Instability.
Patients suffer from a spectrum of instability symptoms.
These can be frank episodes of dislocation to a sensation of the shoulder slipping slightly out of joint which is termed subluxation or just pain.
When patients have recurrent instability symptoms surgery is often indicated. The chances of recurrent dislocation are greater the younger the patient. Teenagers and patients under 20 years have over a 90 % chance of recurrent instability with their active lifestyles. The natural history studies reveal that early surgical intervention decreases the chance of developing recurrent instability.
The goal of surgery is to
- Reattach the detached Labrum and AIGHL to the front of the socket
- Re-tension the AIGHL / capsule which has been stretched from repeated injury
Terms for surgery include Reconstruction or Stabilisation procedures.
The are two approaches to obtain the same goal.
The Arthroscopic technique which involves 2-3 small incisions to obtain portals to inside the shoulder joint.
The Open technique via a traditional incision placed at the front of the shoulder. There is retraction of muscles and detachment of all or part of the anterior rotator cuff muscle (subscapularis tendon) to gain access to the damaged area inside the shoulder.
The current literature reports equivalent results for both Arthroscopic and Open techniques where there is no major bone loss of the socket or large divot in the ball
Both techniques are successful for 8 or 9 patients in every 10 that undergo surgery. Which technique used depends on your individual case and the findings at diagnostic arthroscopy performed at the start of your operation.
Collision athletes – These patients are a problem for all shoulder surgeons. They have a higher incidence than the rest of the population of the operation to stabilise the shoulder failing. These patients are more likely to have problems with fractures of the socket or large divots in the ball part or the shoulder.
Some patients have a loss of bone at the front of their shoulder socket or a large hole in the upper and back portion of their ball part of the Shoulder joint.
In these cases a Bone grafting of the front of the shoulder socket is required. This bone graft has attached to it the biceps tendon.
This procedure is called the Latarjet operation.
It is also useful if you require Revision Shoulder stabilisation.
What is done at surgery?
The anterior part of the shoulder socket, labrum and AIGHL are identified. The anterior socket is freshened to bleeding bone. Next anchors (Bioresorbable / titanium /Peek) are embedded at the front of the socket. These anchors have stitches attached which are utilised to suture the detached structures back to their anatomic position.
Surgery takes approximately 45-90 minutes. Generally you can be discharged that day or sometimes stay 1 night in hospital.
You must wear a sling for 4 – 6 weeks post – operatively.
The most important thing is to never rotate your shoulder outwards beyond pointing the hand straight ahead.
This is necessary to protect the reattached structures while they heal.
After 4 – 6 weeks you can start physiotherapy under the supervision of your physio. A protocol will be given to you.
Contact / Collision sports are not possible for a minimum of 6 months. This is dependent on strength and range of motion. However most patients are not comfortable or able to return for approximately 1 year. The shoulder may be structurally stable but regaining proprioception (the understanding of where your shoulder is and what muscles to contract etc) takes time.
Physical work is not possible for 10-12 weeks. Return to light duties at 10-12 weeks and full duties at 4-6 months post surgery are general guidelines. Desk work is often possible 2 weeks post surgery.
Driving is not allowed by law whilst in a sling regardless of the arm affected.
The surgery is successful in 80 - 90% of people with return to their previous activities.
Complications can include re-dislocation, infection, loss of end range motion, and potentially nerve damage – very rare.
Long term patients with shoulder dislocation can develop arthritis. This is not felt to be a complication of the modern surgical techniques. Patients can develop arthritis from just one dislocation and having never undergone surgery.