Mason initially classified fractures of the radial head at the elbow using a relative simple scheme. This was modified by Morrey to take into account associated soft tissue injuries.
Exclusion: compound fractures
Mason's Classification for Fractures of the Radial Head
Type
fissure or marginal sector fractures without displacement
1
marginal sector fractures with displacement
2
comminuted fractures involving the entire head of the radius
3
where:
• A marginal sector fractures involves a segment of the lateral segment of the radial head.
• A displaced marginal sector fracture may show separation of the fracture fragment, depression and/or being tilted out of line.
• In Morrey's modification, Type 2 fractures involve > 30% of the articular surface and are displaced more than 2-3 mm.
Morrey's Modified Classification
Term
radial head fracture without associated soft tissue injury or fractures
simple
radial head fracture with a ligamentous injury and/or an associated fracture
complex
where:
• Simple fractures are graded using Mason's classification.
• Ligamentous injuries may involve the medial collateral ligament, lateral collateral ligament, or the ligament at the distal radioulnar joint (DRUJ).
• The term "Type 4" fracture was used for a fracture of the radial head that involved dislocation of the elbow joint. This is now referred to as a complex fracture involving the medial and/lateral collateral ligament.
• Injury to the ligament at the DRUJ was described by Essex-Lopresti (J Bone Joint Surgery. 1951; 33B: 244).
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