Anatomy clinical correlates: Clavicle and shoulder

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. 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.

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.