Your shoulder is the most mobile joint in your body, enabling you to reach above your head, lift and rotate your arm and move it in many different directions. Unfortunately, this flexibility makes the shoulder particularly prone to dislocation and after it has dislocated once, your shoulder joint can be vulnerable to repeated full or partial dislocation. We call this chronic shoulder instability.
This article looks at the reasons why recurrent shoulder dislocations occur and the treatments that are available if you are suffering from chronic shoulder instability.
Anatomy of your shoulder
Your shoulder is a ball and socket joint. The ball at the top of your upper arm bone (humerus) fits inside the glenoid, which is the shallow socket in your shoulder blade (scapula). The shoulder capsule is made up of strong connective tissues (including ligaments), which hold the head of the upper arm bone in the correct position and keep the shoulder stable.
Why recurrent dislocations occur
When you dislocate your shoulder, the head of the upper arm bone is forced out of the glenoid socket. It may come partially out of the socket (subluxation) or you may experience a complete dislocation when the ball is wrenched fully out of the socket.
When a dislocation occurs, the ligaments, tendons and muscles around the shoulder joint can tear or loosen. Sometimes the bone of the socket of the ball is also damaged.
This is the reason why dislocations can recur – because the soft tissues that once held the ball firmly inside the socket have become weakened and torn, or the bones have become damaged and lost some of their shape. We refer to this as chronic shoulder instability and the symptoms include a feeling of looseness or weakness in the shoulder, pain and repeated shoulder dislocations.
Causes of chronic shoulder instability
There are three primary causes for chronic shoulder instability:
- Soft tissue injury – This is usually when the labrum, which is the thick rim of cartilage around the edge of the glenoid socket and attaches to the capsule, becomes detached. The most common type of tear is called a Bankart lesion. When this happens the shoulder may feel unstable or weak, and recurrent dislocations can result. In older patients there may also be a tear of the rotator cuff tendons, which also contributes to instability.
- Hyperlaxity – Some people are born with looser ligaments in their shoulder joint, while others can develop looseness of the ligaments as the result of making repetitive overhead motions (for example, playing tennis or volleyball, or swimming). When ligaments loosen, the stability of the shoulder is compromised and if you continue making repetitive movements or placing the joint under stress, it can become unstable.
- Bone injury – Occasionally the rim of the socket will fracture instead of the labrum tearing, this is called a Bony Bankart lesion. The larger the broken piece the worse the instability that follows. In cases of repeated dislocations, the bone at the back of the humeral head can become eroded (Hill-Sachs lesion), making further dislocations even more likely due to the loss of the normal contour of the ball.
Diagnosing chronic shoulder instability
You will normally undergo a range of imaging tests including X-rays, which can show damage to the bones of your shoulder joint, and MRI scans which can identify injuries to the ligaments and tendons, and/or CT scan to show any associated bone damage. Often dye is injected into the shoulder joint before the MRI or CT scan to show up the anatomy better (arthrogram). People over the age of 40 are at greater risk of developing a rotator cuff tear if they sustain a dislocated shoulder so it is important to get an accurate diagnosis. An ultrasound or MRI scan is recommended to assess this as soon as possible after the injury.
Treatments for recurrent shoulder dislocations
If you are experiencing chronic shoulder instability, you may need to make some short term activity modifications to protect your shoulder joint and avoid further dislocations. Anti-inflammatory medication can help to relieve pain and swelling and you may need to see a physiotherapist who can recommend exercises to build strength in your shoulder and increase stability.
If you are experiencing repeated dislocations, there are different surgical procedures available, including:
- A Bankart labral repair is a keyhole procedure used to treat a Bankart lesion. Bone anchors are placed in the socket with attached sutures to repair the torn labrum. Keyhole technique minimise muscle damage during surgery and have the added advantage of being able to address a significant Hill-Sachs lesion using a technique called remplissage. This has been show to increase the success rate of surgery.
- The Latarjet Procedure – If the injury to your shoulder includes significant bone damage, or the problem has recurred after a Bankart repair, you may require a Latarj
ct procedure. This involves detaching a nearby piece of bone and transferring it to the damaged area in your shoulder socket.
If you have dislocated your shoulder and are worried about developing shoulder instability or if you have experienced recurrent dislocations, talk to us about a diagnosis and possible treatment options.
Related Reading | Shoulder Dislocations:
Do I Need Surgery After a Shoulder Dislocation?
What Type of Surgery Might be Needed After a Shoulder Dislocation?
Orthopaedic Consultant & Surgeon | London
Thames Shoulder & Elbow are able to provide advice and support to anyone experiencing symptoms affecting the upper limbs (shoulder, upper arm, elbow, forearm and wrist).
Telephone: 020 376 15987
Email: admin@thamesshoulderandelbow.co.uk
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