Anatomy clinical correlates: Clavicle and shoulder

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Introduction0:00–0:26

Our upper limbs are complex structures. They’ve got bones, muscles, fascia, nerves and blood vessels, and everything in between.
Our upper limbs are prone to injury however, and oftentimes, even a small injury can have a huge functional deficit as we are so reliant on our upper limbs in everyday life.
One of these commonly injured areas is the shoulder region. Ok, so let’s start by taking a look at the injuries of the clavicle.

Clavicle fractures0:26–1:44

Because of its subcutaneous position, the clavicle is prone to fractures, which are usually the result of direct or indirect trauma.
An example of direct trauma is falling directly on the shoulder. Indirect trauma, however, may occur when falling on an outstretched hand, and the force of impact is transmitted through the bones of the forearm and the arm to the shoulder, which can result in a clavicle fracture.
Most of these fractures occur in the middle third of the clavicle, particularly where the middle third meets the lateral third, which is the weakest point of the clavicle.
So with clavicular fractures, the medial fragment is usually pulled up by the sternocleidomastoid muscles, which can be apparent to the naked eye and palpable.
At the same time, the trapezius muscle is having trouble holding the lateral fragment up, because of the weight of the limb, so the shoulder drops.
And since the two fragments may glide under each other, the clavicle is also shortened. Additional features may signal complications of a clavicle fracture.
For example, if the skin above the fracture seems to be tenting, meaning it looks like a tent, that suggests the fracture may become an open fracture in the future, and warrants surgical stabilization.

Acromioclavicular dislocation1:44–3:05

Alright, now, another thing that can happen in this region is an acromioclavicular dislocation, also called a “shoulder separation”.
Just like the name says, the clavicle and acromion process separate, usually because of a direct blow to the shoulder, or a fall landing directly on the shoulder joint.
And this may be seen in contact sports, like football, soccer or hockey. In most cases, the dislocation is mild if the acromioclavicular ligament is just stretched or partially torn.
In severe cases, both the acromioclavicular ligament and the coracoclavicular ligaments are torn. If the coracoclavicular ligament tears, the shoulder can completely separate and drop due to the weight of the upper limb.
If the joint capsule also tears, the acromion process may slip under the clavicle. Clinically, there is swelling of the acromioclavicular joint, and pain that worsens with overhead arm movement and lying on the affected side.
You can also get osteoarthritis of the acromioclavicular joint, often the result of a previous injury. To test pathology of the AC joint, the scarf test may be used, where the arm of the affected joint is flexed and adducted across the chest and neck, similar to a scarf, producing pain over the AC joint.

Glenohumeral joint/Shoulder dislocation3:05–5:01

Now, right below the acromioclavicular joint, there’s the glenohumeral, or shoulder joint, which is a ball and socket joint, where the ball is the humeral head, and the glenoid cavity of the scapula is the socket.
The joint is supported by ligaments, and surrounded by the rotator cuff muscles, commonly remembered with the SITS mnemonic: supraspinatus, infraspinatus, teres minor, and subscapularis.
The glenohumeral joint is freely movable, which lets us make complex movements like throwing a baseball, but this also means that this joint is highly unstable.
So, one thing that can happen is a glenohumeral joint dislocation, which can be anterior, meaning the humeral head is dislocated towards the front, or posterior, when the humeral head is dislocated towards the back.
Anterior dislocations are more common in young people, and they occur because of a direct blow, or a fall on an outstretched arm.
Think of a soccer goalkeeper jumping to catch the football, arms outstretched, and landing right on his side. This usually happens when the arm is externally rotated and abducted, and when there is a hard blow to the humerus, the humeral head gets pushed down towards the weaker inferior part of the joint capsule.
If it tears or weakens, the humeral head goes inferiorly, and the strong flexors and adductors pull it forward. Clinically, the shoulder is visibly displaced and may appear “squared off” since the curvature of the deltoid muscle is lost.
One possible complication to be aware of is damage to the axillary nerve, which is located inferior to the glenohumeral joint.
Axillary nerve damage causes a loss of sensation over the lateral part of the proximal arm and atrophy of the deltoid muscle resulting in weakness of abduction of the shoulder.
Posterior dislocations, on the other hand, are rare, and they usually happen because of forceful muscle contraction during an electric shock or seizure.

Rotator cuff Injuries5:01–5:52

One issue that’s commonly associated with a shoulder dislocation is a rotator cuff injury. But rotator cuff injuries may also occur on their own.
Degenerative injuries of the rotator cuff occur in the context of repetitive stress, such as in sports like baseball or tennis, or occupations that require repetitive overhead movements.
This causes a lot of inflammation and an accumulation of small tears in the tendons overtime. The most commonly injured tendon is the supraspinatus tendon, which can become impinged as it passes between the acromion process and the humeral head during abduction.
This space is already very small, so anything that makes this space smaller, like inflammation, bone spurs of the inferior part of the acromion, or subacromial bursa inflammation, can cause the tendon to become repetitively impinged and irritated.
In rotator cuff impingement, also called tendinopathy, these damaged tendons result in constant pain with movements such as abduction, external rotation, and internal rotation.

Rotator cuff impingement5:52–6:55

However, typically, the individual has normal range of motion. The “empty can” or “full can” tests can help assess for supraspinatus tendinopathy, where the patient has their arm raised parallel to the ground in the scapular plane, either in internal rotation for the “empty can” or in external rotation for the “full can” test.
The examiner then pushes down at the elbow or wrist while the patient resists. The test is positive if there is weakness and/or pain.
Other tests of subacromial impingement are the Neers test, where the individuals arm is internally rotated and passively flexed forward above their head to elicit pain, and the Hawkins Kennedy test, where the individual bends their elbow to 90 degrees, flexes their arm to 90 degrees, and is put into internal rotation to elicit pain.

Rotator cuff tear6:55–7:38

On the other hand, acute injuries that occur when falling on an outstretched arm, or when lifting something heavy with a jerking motion, can result in a rotator cuff tear.
Instead of pain on movement, individuals with rotator cuff tears may have pain and weakness during abduction, external rotation, or internal rotation.
If it’s severe enough, they may have significant movement deficits. The most common rotator cuff tear is to the supraspinatus, and can be tested with the drop arm test.
With the patient holding their arm abducted above the head, when they’re asked to lower it slowly, they will be unable to do it smoothly and will have a rapid drop around mid-descent.

Glenohumeral Osteoarthritis7:38–8:02

In addition to tendinopathy and rotator cuff tears, the glenohumeral joint is also prone to osteoarthritis. This results in the gradual onset of anterior and deep shoulder pain, and also causes a decrease in active and passive range of motion of the shoulder.
Risk factors for glenohumeral osteoarthritis are age, trauma, and previous shoulder injuries. Next, there’s adhesive capsulitis, or “frozen shoulder”, which is when connective tissue around the glenohumeral joint, mainly the joint capsule, gradually becomes inflamed and stiff, usually in people between the ages of 40 and 60.

Adhesive capsulitis8:02–8:56

This process may be initiated by injuries like glenohumeral dislocations, or rotator cuff injuries, as well as many others.
Clinically, there are usually three stages. In the first stage there is disabling pain and increasing stiffness for up to 9 months.
The second phase is characterized by progressive range of motion limitation, to the point where both passive and active movement is nearly impossible, but the pain is less pronounced.
This phase can last up to 12 months. And lastly, the third phase is the recovery phase where patients regain their mobility, which can take up to 2 years.
Finally, let’s look at one of the more famous structures crossing the shoulder joint, which is the biceps tendon. Most often prolonged tendonitis of the biceps tendon weakens it over time, where it can rupture, resulting in a biceps tendon rupture.

Biceps tendon rupture8:56–9:40

It can also be damaged during forceful flexion of the arm against resistance such as weight lifting. The rupture typically occurs at or near the proximal supraglenoid attachment, and is associated with a loud pop.
The detached muscle belly then forms a ball distally near the lower anterior aspect of the arm, commonly referred to as a ‘popeye deformity’ - so take it easy when you’re at the gym!Allright, as a quick recap...

Review9:40–11:27

Clavicular fractures may result from direct or indirect trauma. They often occur in the middle third of the clavicle, and result in shoulder drooping and a shortened clavicle.
Another injury of the shoulder girdle is acromioclavicular dislocation, which is usually the consequence of a direct blow to the shoulder.
And this may be seen in contact sports, like football, soccer or hockey. Then, there’s glenohumeral dislocation.
Anterior glenohumeral dislocations occur because of a direct blow to the shoulder, or falling on an outstretched arm. Clinically, the shoulder is visibly displaced and may appear “squared off” since the curvature from the deltoid muscle is lost.
Posterior dislocations are rare, and they usually happen because of forceful muscle contraction during an electric shock or seizure.
Repetitive activity above the head can lead to impingement and tendinopathy of the rotator cuff muscles, most frequently affecting the supraspinatus muscle resulting in pain on movements.
Rotator cuff tears are similar to tendinopathies but result in pain and weakness of movements, again with the supraspinatus being the most commonly injured.
The glenohumeral joint is also susceptible to osteoarthritis, resulting in gradual onset of pain and decreased range of motion.
Adhesive capsulitis, also known as frozen shoulder, occurs due to inflammation and resulting stiffness of the connective tissue like the joint capsule around the glenohumeral joint.
The biceps tendon can also rupture, most often at or near its proximal attachment, often due to long standing tendonitis or forced flexion against resistance, resulting in the characteristic ‘popeye deformity’.