Modern Study Review (AI-Generated)
High-Yield Summary
The AO/OTA 23 classification pertains to distal radius and ulna fractures, a common injury site with significant functional impact on wrist motion and load transmission. This classification stratifies fractures by articular involvement and complexity, guiding surgical decision-making between conservative management, ORIF, or external fixation. Understanding the fracture morphology (extra-articular, partial articular, complete articular) is critical to determine the need for absolute stability (anatomic reduction and compression) versus relative stability (bridge plating or splintage).
Anatomy & Coding Foundation
- AO Code: 23 — Distal segment of the Radius and Ulna
- Bone: Radius (primary focus), Ulna (styloid and distal shaft)
- Segment: 3 (distal)
- Morphology Types:
- A: Extra-articular fractures (radius and/or ulna)
- B: Partial articular fractures (involving part of the radius articular surface)
- C: Complete articular fractures (articular surface and metaphysis disrupted)
Classification Details
| AO Type | Subtype | Description | Injury Mechanism | Stability Profile |
| A | 23-A1 | Extra-articular ulna fracture only | Low-energy fall, direct trauma | Generally stable |
| 23-A2 | Extra-articular simple radius fracture, impacted | Axial load with impaction | Stable to moderately stable | |
| 23-A3 | Extra-articular comminuted radius fracture | High-energy trauma | Unstable | |
| B | 23-B1 | Partial articular sagittal fracture of radius styloid | Varus/valgus with rotational force | Moderately stable |
| 23-B2 | Partial articular dorsal rim fracture of radius | Hyperextension injury | Unstable | |
| 23-B3 | Partial articular volar rim fracture of radius | Hyperflexion injury | Unstable | |
| C | 23-C1 | Complete articular simple articular + metaphyseal fracture | High-energy axial load | Unstable, requires fixation |
| 23-C2 | Complete articular simple articular + comminuted metaphysis | High-energy trauma | Highly unstable | |
| 23-C3 | Complete articular comminuted articular fracture | Severe trauma | Highly unstable |
Management Logic
- Operative Indications:
- Type A: Usually non-operative unless displaced or unstable (A3).
- Type B: Often require ORIF to restore articular congruity and stability.
- Type C: Almost always require surgical fixation (ORIF or external fixation) due to articular involvement and instability.
- Fixation Principles:
- Absolute Stability: Required for articular fractures (Types B and C) to allow early motion and prevent post-traumatic arthritis. Achieved by compression plating or lag screws.
- Relative Stability: Acceptable for extra-articular comminuted fractures (A3) using bridge plating or intramedullary devices.
Prognostic Factors
- Type A: Generally good prognosis with low non-union rates; comminution increases risk of malunion.
- Type B: Risk of post-traumatic arthritis if articular step-off >2 mm; early anatomic reduction improves outcomes.
- Type C: Highest risk of complications including non-union, stiffness, and arthritis; prognosis depends on quality of articular reduction and metaphyseal reconstruction.
Classic Clinical Notes
23-Radius/Ulna Distal
- A-Extra-articular
- 23-A-1: Ulna fracture, radius intact
- 23-A-2: Radius simple + impacted fracture
- 23-A-3: Comminuted radius fracture
- B-Partial Articular
- 23-B-1: Sagittal radius (styloid) fracture
- 23-B-2: Frontal radius dorsal rim fracture
- 23-B-3: Frontal radius volar rim fracture
- C-Complete Articular of radius
- 23-C-1: Simple articular & metaphyseal fracture
- 23-C-2: Simple articular & comminuted metaphysis
- 23-C-3: Comminuted articular fracture
Last Updated on January 25, 2026 by Christian Veillette
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