Shoulder dislocation

Introduction

The shoulder is the most commonly dislocated joint in the body. Dislocations of the shoulder in young adults and in older adults result in different problems. In young adults, an initial shoulder dislocation may result in weakening of the shoulder such that the patient is prone to dislocations again in the future (recurrent dislocations). Often times less force is required to cause the shoulder to dislocate again subsequently. Some patients have such severe instability that the shoulder may dislocate spontaneously even while sleeping or reaching out or up. This section will discuss the problem of shoulder dislocation in young adults. In older adults, an initial shoulder dislocation may cause tendons in the shoulder to tear (the rotator cuff). Rotator cuff tears in older adults may then cause either recurrent shoulder dislocations (similar to young adults but due to a different cause) or may result in chronic pain and weakness in the shoulder. Click here to learn more about rotator cuff tears.

Anatomy of the Shoulder Joint

Bony anatomy of the shoulder
Bones that make up the shoulder

The shoulder joint is made up of 3 bones: the shoulder blade (scapula), the humeral head and the collar-bone (clavicle).

Shoulder joint
The scapula and humerus in their natural position behind the ribcage

Movements around the shoulder involve 3 separate articulations: the glenohumeral joint, the acromioclavicular joint and the scapulothoracic articulation. When the arm is raised, the majority of movement occur at the glenohumeral joint and the scapulothoracic articulation.

Shoulder joint with intact labrum
Ligaments spanning the labrum and the humerus have not been shown to demonstrate the labrum more clearly

The glenohumeral joint is a ball and socket joint, comprising the socket (the glenoid) and the ball (the humeral head). Both surfaces of the joint are covered with an extremely smooth and rubbery cartilage (known as articular cartilage). The smooth surfaces create a frictionless articulation when lubricated with a small amount of joint fluid.

The glenoid is really a rather shallow socket. In fact, a dish is probably a more accurate description! This, however, is a design which is intended to allow the shoulder joint to have great range of movement. Unfortunately, the price of big range of movement is stability. You can probably image that a big ball sitting on a shallow dish will fall off very easily. While that is true to a certain extent, the body has ways of preventing this from happening. A ring of cartilage attached to the rim of the glenoid helps to not only deepen the socket, but also serves as the attachment point of ligaments that help to hold the humeral head in place. This ring of cartilage is known as the labrum. The view of the glenoid seen end-on further demonstrates the labrum. Note: Ligaments attaching the labrum and glenoid to the humeral head are not shown in order to allow readers to appreciate the importance of the labrum.

Glenoid labrum end on view
End on view of the glenoid with normal labrum

The view of the glenoid seen end-on further demonstrates the labrum. Note: Ligaments attaching the labrum and glenoid to the humeral head are not shown in order to allow readers to appreciate the importance of the labrum.

What is a shoulder dislocation?

Normal shoulder, anterior dislocation, posterior dislocation
Different types of dislocation

A shoulder dislocation refers dislocation of the glenohumeral (ball and socket) joint. That means the ball (humeral head) is no longer sitting nicely in the socket (glenoid), but rather has “fallen off” the socket. As you might guess, the ball can possibly “fall off” in any direction, i.e. to the front, the back, the bottom etc. But in reality, anteroinferior dislocations (the ball falls off to the front and bottom of the socket) are by far the most common.

What happens after a shoulder dislocation?

Anterior labral tear
Pictoral representation of a Bankart tear

In a shoulder dislocation, the humeral head gets pushed out of the socket and that often causes the labrum to get torn off the rim of the socket. Such an injury is known as an anterior labral tear or a Bankart lesion (named after the doctor who described this tear). Often times the front of the glenoid slams into the back of the humeral head with such force that a dent is made in the humeral head. This dent is known as a Hill-Sachs lesion. This dent is usually not significant and will not be discussed further in this article. The Bankart lesion caused by the dislocation often does not heal and remains detached from the glenoid rim. As a result, stability previously conferred by the presence of the labrum is lost, rendering the shoulder unstable.

How does a shoulder dislocation occur?

Sports injuries are a common cause of shoulder dislocation. This may occur in various types of sports. Examples include; slipping during rock climbing resulting in a large yanking force on the arm holding on to a grip, reaching out to block an opponent running past during rugby or basketball, fall with the arm held out in an awkward angle etc. There will be sudden severe pain and the patient will not be able to move the shoulder after. Sometimes the dislocated shoulder snaps back into position by itself, but sometimes it does not. The patient will then have to seek help to get the shoulder put back in place.

I have a dislocated shoulder. How do I put it back in?

You will need to seek help either at a family clinic or at the emergency department of a hospital. However, not all family physicians have the sedatives or experience to do this procedure. I would advise against doing it yourself or getting your friend to do a quick google consult and perform it! The reason is that sometimes other conditions such as acromioclavicular joint dislocations and even fractures or fracture-dislocations can be easily mistaken for a "typical" glenohumeral joint dislocation. Attempts to fix the dislocation will not only be extremely painful, they will at best be ineffective and may even worsen the injury.

Your doctor will need to examine your shoulder to ensure that there is, indeed a dislocated shoulder. If it is an obvious “classic” case, he may directly attempt manoeuvres to put it back in. Often, though, he will confirm the presence of a shoulder dislocation before attempting to put it back. A simple x-ray will easily confirm the diagnosis.

The procedure is often done under conscious sedation; this means the doctor will administer drugs to get you all woozy and to overcome the strong muscle spasm around the shoulder that often prevents it from getting put back in easily. Once you are sufficiently sedated, the doctor can then gently put the shoulder back in.

It is back in. What now?

If you are young (late teens or in your twenties), there is a significant change your shoulder can become unstable in the future, unfortunately. Some estimate the chances of this to be 60 – 70%. Shoulder instability in the future can manifest in a couple of ways. In some patients, the shoulder dislocates again. In others, they may experience pain during sports. There are usually few functional deficits in normal daily life, except in patients with very unstable shoulders. In these patients, their shoulders may dislocate even with simple every day activities like lifting their arms overhead, putting their hands behind their heads, even sleeping!

My shoulder has become unstable. Why has this happened?

End on view of Bankart tear (anterior labral tear)
End on view of the glenoid with a Bankart or anterior labral tear

The most common reason is that you have torn the labrum of your shoulder. This is also known as a Bankart lesion. The tear has not healed or sometimes, the labrum becomes scarred and stuck down to the neck of the glenoid (the part of the bone beneath the rim of the glenoid). Because of this, the usual restraint against dislocation provided by the labrum is no longer working and the shoulder is easily dislocated again. Although this is the most common reason why your shoulder has become unstable, it is not the only one.Sometimes the force of the dislocation knocks off the rim of the glenoid, resulting in a defect at one part of the rim. In other cases, the force of the dislocation also causes the back of the ball to bump into the rim of the socket, causing a dent to form in the back of the ball. This is known as a Hill Sachs lesion (pronounced “hill-sacks”). If the Hill Sachs lesion is large and deep enough, the rim of the glenoid may “fall into” the Hill Sachs lesion during movements, predisposing the patient to recurrent dislocations. You should seek help from your orthopaedic doctor.

What will the doctor do?

He will need to further assess you to find out the reason why your shoulder has become unstable. It is hence important for the doctor to differentiate between the different causes of dislocation in order to recommend the most suitable treatment for you.

How are unstable shoulders resulting from Bankart lesions treated?

End on view of Bankart repair (labral repair)
End on view of a glenoid with repaired Bankart lesion

If your shoulder has dislocated more than once previously, it is almost certainly going to dislocate again in the future. Physiotherapy alone, is not likely to reduce or prevent future dislocations. It is hard to predict when or how often your shoulder will dislocate. Often when patients are doing activities and are aware that their shoulders might be at risk of dislocating, they are able to either engage the muscles in their shoulders to stabilize the shoulder. But dislocations often occur when patients are not expecting it and hence cannot take measures to actively prevent it.  The most reliable way of preventing future dislocations is via a keyhole surgery known as an arthroscopic Bankart repair. During this surgery, the torn labrum is identified and any scar tissue that has formed between the labrum and the glenoid rim is released and removed. The labrum is then brought back in apposition with the glenoid rim and secured in place. To secure the labrum, it is possible to pass sutures through the substance of the labrum because the labrum is rubbery in consistency and this is easily achieved using a needle. However, in order to secure the labrum onto the glenoid rim (which is bone), it is necessary to drill tiny holes in the rim in order to insert small implants known as suture anchors. These suture anchors are made of either medical grade plastic or balls of suture material that expand and wedge themselves tightly in the holes (in the bone). There is no need to remove these suture anchor in the future.

Will I be able to participate in sports after the surgery?

Absolutely. The aim of the surgery is to restore stability to your shoulder, not just during daily activities, but also during sports.

What should I do now?

If you have managed to get to this part of this long article, your shoulder must be bothering you significantly! Consult your family doctor or see an orthopaedic specialist and he/she should be able to advise you accordingly.

Disclaimer:

The above information is meant to be used as a guide and for patient education purposes. This article is not meant to be a used for self diagnosis or a substitute for professional medical evaluation or advice. As patients may be differing symptoms, please see your family doctor or orthopaedic specialist if you have any symptoms or worries.

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