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High-Yield Summary
The AO/OTA 22 classification addresses diaphyseal fractures of the radius and ulna, critical for forearm stability and function. Accurate classification guides the choice between absolute stability (compression plating) and relative stability (bridge plating or external fixation). The system distinguishes simple, wedge, and complex fracture patterns, which directly influence surgical strategy and prognosis.
Anatomy & Coding Foundation
- AO Code: 22 = Radius and Ulna Diaphysis (shaft)
- Bone/Segment:
- 2 = Radius/Ulna
- 2 = Diaphyseal (shaft) segment
- Morphology Types:
- A: Simple fracture (single fracture line)
- B: Wedge or segmental fracture (one or more intermediate fragments)
- C: Complex fracture (multifragmentary, comminuted)
Classification Details
| AO Type | Subtype | Description | Injury Mechanism | Stability Profile |
| A | A1 | Simple ulna fracture, radius intact | Low-energy direct trauma | Stable if isolated |
| A2 | Simple radius fracture, ulna intact | Low-energy direct trauma | Stable if isolated | |
| A3 | Simple fractures of both bones | Higher energy, direct or indirect | Potentially unstable due to loss of both bone integrity | |
| B | B1 | Segmental ulna fracture, radius intact | High-energy trauma, bending + torsion | Unstable, intermediate fragment(s) present |
| B2 | Segmental radius fracture, ulna intact | High-energy trauma | Unstable | |
| B3 | Segmental fracture involving one or both bones | High-energy trauma | Highly unstable | |
| C | C1 | Complex ulna fracture | High-energy, comminution | Unstable, multifragmentary |
| C2 | Complex radius fracture | High-energy, comminution | Unstable | |
| C3 | Complex fractures of both bones | Severe trauma, comminution | Highly unstable |
Management Logic
- Operative Indications:
- All Type B and C fractures generally require surgical fixation due to instability and risk of malunion/nonunion.
- Type A fractures with displacement or both bones fractured (A3) typically require ORIF.
- Intramedullary nailing is less common due to rotational instability; plating remains the gold standard.
- External fixation reserved for open fractures or severe soft tissue injury.
- Fixation Principles:
- Absolute Stability (Compression Plating): Preferred for simple (Type A) fractures to promote primary bone healing.
- Relative Stability (Bridge Plating or External Fixation): Used for wedge (Type B) and complex (Type C) fractures to preserve blood supply and allow secondary healing.
Prognostic Factors
- Type A fractures: Low nonunion rates if anatomically reduced and rigidly fixed.
- Type B fractures: Increased risk of delayed union due to intermediate fragments; fixation must maintain length and rotation.
- Type C fractures: Highest risk of nonunion and malunion; soft tissue damage and comminution complicate healing.
- Functional outcome correlates with restoration of radial bow and forearm rotation.
Classic Clinical Notes
22-Radius/Ulna Diaphysis
- A-Simple fracture
- 22-A-1: Ulna fracture, radius intact
- 22-A-2: Radius fracture, ulna intact
- 22-A-3: Both bones fractured
- B-Segmental/Wedge
- 22-B-1: Ulna fracture, radius intact
- 22-B-2: Radius fracture, ulna intact
- 22-B-3: One or both bones segmental
- C-Complex fracture
- 22-C-1: Ulna fracture
- 22-C-2: Radius fracture
- 22-C-3: Both bones fractured
Last Updated on January 25, 2026 by Christian Veillette
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