Clavicle Fracture
Clavicle fractures are common and are divided according to anatomical location:
- Middle third, approximately 70% to 80%
- Distal third
- Medial third
Most fractures occur after direct impact to the shoulder.
The middle third is most vulnerable because it is narrow, lacks muscular reinforcement and lies between the stabilising ligamentous complexes.
Allman classification
Group I
Middle third fracture.
Group II
Distal third fracture.
Group III
Medial third fracture.
The classification is anatomical but does not adequately describe stability of distal fractures.
Modified Neer classification for distal clavicle fractures
The relationship between the fracture and coracoclavicular ligaments determines stability.
Type I
Fracture lateral to the coracoclavicular ligaments.
Ligaments remain intact.
Usually minimally displaced and stable.
Type IIA
Fracture medial to the coracoclavicular ligaments.
Conoid and trapezoid remain attached to the distal fragment.
The proximal fragment displaces because it has lost coracoclavicular restraint.
Unstable.
Type IIB
Fracture occurs around the coracoclavicular ligament complex with loss of effective conoid restraint.
Unstable and associated with high nonunion risk.
Type III
Fracture extends into the acromioclavicular joint but coracoclavicular ligaments remain intact.
Usually stable.
Type IV
Paediatric physeal injury with intact periosteal sleeve.
Type V
Comminuted distal fracture with an inferior fragment attached to the coracoclavicular ligaments while the medial fragment is displaced.
Unstable.
Types I, III and many IV injuries are usually stable. Types II and V are mechanically unstable and have higher nonunion rates.
