A 32-year-old with a Monteggia fracture-dislocation has a proximal ulna fracture with dislocation of the radial head. According to Bado's classification, a Type I pattern involves:

• A Posterior radial head dislocation with apex-posterior ulna fracture
• B Lateral radial head dislocation with ulna fracture
• C Anterior dislocation with radial shaft fracture
• D Anterior radial head dislocation with apex-anterior ulna fracture ✓

Explanation

In Bado's classification of Monteggia fracture-dislocations: Type I (most common, ~60%) — anterior dislocation of the radial head with apex-anterior (apex-forward) fracture of the ulnar shaft; Type II — posterior/posterolateral radial head dislocation with apex-posterior ulna fracture; Type III — lateral/anterolateral dislocation with metaphyseal ulna fracture (most common in children); Type IV — anterior dislocation with fractures of both the ulna and radius. The apex of the ulnar fracture generally points toward the direction of radial head dislocation.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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