Anatomical and biomechanical features
The clavicle and scapula form the bony foundation of the pectoral girdle. Unlike the scapula, fractures of which are rare (only 1–2.5%) thanks to the protection of the muscular mass, the clavicle fractures frequently. This is due to its subcutaneous location and the fact that it serves as a rigid strut connecting the arm to the thorax.
The clavicle forms two important joints:
- Acromioclavicular (with the scapula). Its stability is ensured by the acromioclavicular and coracoclavicular ligaments.
- Sternoclavicular (with the axial skeleton). Fixed by the sternoclavicular and costoclavicular ligaments.
In the middle third, the bone has a pronounced S-shaped curve along its axis. It is precisely here, near its inferior surface, that vital anatomical structures pass: the subclavian artery and vein (a. et v. subclavia), as well as the trunks of the brachial plexus (plexus brachialis).
Mechanisms of injury
A fracture can occur in two ways, which determine the nature of the injury:
- Indirect mechanism (dominant). The injury occurs during a fall onto an outstretched hand, onto the lateral surface of the shoulder, or during sudden lateral compression of the shoulder joints. The load is transmitted from the acromion along the entire clavicle. Due to its S-shape, the bone breaks at the site of greatest curvature (in the middle third).
- Direct mechanism (less common). Occurs from a local impact directly to the clavicle. Usually, this leads to the formation of oblique or oblique-transverse fractures.
Typical fragment displacement
If the fracture is localized in the middle third, the fragments are displaced in a strictly defined scenario under the influence of muscle traction and the weight of the limb itself. As a result, they are positioned at an angle open anteriorly and inferiorly.
- Central fragment: contraction of the sternocleidomastoid muscle (m. sternocleidomastoideus) pulls it superiorly and posteriorly.
- Peripheral (lateral) fragment: under the weight of the arm and due to muscle traction, it is displaced inferiorly and anteriorly.
Features of distal end fractures: In this zone, the peripheral fragment often maintains its connection with the acromion and coracoid process of the scapula. The central fragment, meanwhile, moves upward, which is clinically masked as an acromioclavicular joint dislocation. Incomplete intra-articular and periarticular fractures here may be accompanied by rupture of the superior acromioclavicular and coracoclavicular ligaments.
Clinically important: sharp edges of displaced bone fragments can pierce the skin, damage the pleural dome, or injure the neurovascular bundle.
Clinical presentation and diagnostics
Diagnosis is usually straightforward due to the superficial location of the clavicle. The physician relies on the following data:
Patient complaints:
- Local pain in the fracture area.
- Sharp restriction of active movements (the patient cannot abduct or elevate the arm due to pain syndrome).
Objective symptoms:
- The supraclavicular fossa is smoothed out due to pronounced deformity.
- Bruising is visible.
- The shoulder girdle on the injured side appears shortened.
Reliable signs of a fracture:
- Pathological bone mobility outside of a joint.
- Bone crepitus (characteristic crunching upon palpation).
- Clear visual and palpable definition of sharp bone fragment edges under the skin.
Briefly: answers to topical questions
Which specific muscles cause the displacement of the peripheral clavicle fragment downward and medially?
Displacement of the peripheral (lateral) clavicle fragment downward, forward, and medially occurs due to the weight of the upper extremity and the traction of the pectoral muscles. The specific anatomical names of the muscles causing this displacement are not detailed in the sources.
For comparison, the displacement of fragments in diaphyseal fractures looks as follows:
- Peripheral fragment — displaced downward, forward, and medially under the action of the arm's weight and pectoral muscles.
- Central fragment — displaced upward and posteriorly as a result of the contraction of the sternocleidomastoid muscle (m. sternocleidomastoideus).
What are the absolute indications for surgical treatment (osteosynthesis) of a clavicle fracture?
Absolute indications for surgical treatment of clavicle fractures include:
- open fracture;
- closed comminuted fracture with rotation of the fragment perpendicular to the axis of the clavicle and the threat of neurovascular bundle injury;
- closed fracture complicated by injury or compression of the neurovascular bundle;
- danger of skin perforation from the inside by the sharp end of the fragment, if this is not resolved conservatively;
- various types of interposition;
- pathological fracture;
- clavicle fracture as part of polytrauma;
- flail shoulder.
What types of immobilizing bandages are used for conservative treatment of clavicle fractures?
For conservative treatment and immobilization of clavicle fractures, the following are used:
- sling bandage;
- Desault bandage;
- Smirnov-Weinstein plaster cast;
- figure-of-eight bandage;
- Delbet rings;
- Chizh frame after reposition of displaced fractures.
Delbet rings and the figure-of-eight bandage are indicated for fractures without displacement. In pediatric traumatology, the figure-of-eight bandage is most widely used.
In which radiographic projections is an image taken to confirm a clavicle fracture?
To confirm a clavicle fracture, the standard method is radiography in the anteroposterior (straight) projection. In most cases, this examination is sufficient to make a diagnosis.
Additionally, the following projections are used:
- Anteroposterior projection with a 20° beam tilt is performed to assess the degree of clavicular shortening.
- Rockwood view is a radiography technique with the beam angled 40° cranially, used when injury to the sternal end is suspected.
- Comparative radiographs are imaging views of the contralateral side to evaluate the acromioclavicular joint.
- Stress radiography involves imaging with a 2.0–5.0 kg load to assess vertical stability.
To easily remember the displacement in a clavicular fracture, imagine a mechanical balance: the central part is pulled UP by a strong neck muscle (the sternocleidomastoid), while the outer part drops DOWN simply due to the weight of the arm itself.
Class and exam questions
Why are clavicle fractures significantly more common than scapular fractures?
The clavicle acts as a rigid strut between the shoulder girdle and the chest wall, lacking robust muscular protection. The scapula, by contrast, is highly mobile, protected by a muscle mass, and excellent at absorbing kinetic energy.
Which anatomical structures are at risk of injury from a displaced clavicle?
Near the inferior surface of the clavicle (in the middle third) run the subclavian artery and vein (a. et v. subclavia), the brachial plexus (plexus brachialis), and the closely situated pleural dome.
What can a fracture of the lateral end of the clavicle be confused with?
Because the central fragment displaces upward while the peripheral fragment remains connected to the scapula, the visual appearance often mimics a dislocation of the acromial end of the clavicle.
What else to study on this topic
- Pre-hospital care: immobilization with a sling and a Desault bandage
- Principles of conservative management: types of stabilizing abduction braces
- Indications for surgical treatment of shoulder girdle fractures
- Radiological evaluation and computed tomography in complex trauma
- Scapular fractures: classification, mechanism of injury, and associated rib injuries
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