Causes / typical injury mechanism: Capitellum fracture most commonly occurs when an individual falls on an outstretched hand (FOOSH) with the elbow in a semiflexed position. It could also be caused by a direct blow to the lateral elbow while the elbow is flexed and the capitellum is more vulnerable to injury.

Classic history and presentation: The patient typically presents after a fall with pain and limited range of motion (ROM) of the elbow. Point tenderness and pain over the lateral elbow with passive rotation and an elbow effusion will be present. A gross deformity may be visible.

Prevalence: This is a rare injury, comprising 1%-2% of all elbow fractures.

• Age – This is more common in individuals 12 years and older, with no distribution.
• Sex / gender – There is a female predominance.

Risk factors: Female sex, due to increased carrying angle, greater prevalence of cubitus recurvatum, or osteoporosis.

Pathophysiology: A FOOSH while the elbow is partially flexed creates a shearing force from the radius across the capitellum, inducing a fracture.

Grade / classification system: Bryan and Morrey classification (with McKee modification).

Type I:

• Large osseous piece of capitellum with or without trochlear involvement.
• Most common.

Type II:

• Shear fracture articular cartilage.
• Articular cartilage separation with little subchondral bone attached.

Type III:

• Severely comminuted, multifragmentary.
• Commonly associated with radial head fractures.

Type IV (McKee addition):

• Coronal shear fracture involving both capitellum and trochlea.