A
Fracture of the proximal third of the ulna with dislocation of the radial head
B
Fracture of the distal third of the radius with disruption of the distal radioulnar joint (DRUJ)
C
Fracture of the radial head with dislocation of the proximal radioulnar joint
D
Isolated fracture of the ulnar shaft
Explanation:The correct option is 'a'. A Monteggia fracture-dislocation is characterized by a fracture of the ulnar shaft (typically the proximal third) associated with a dislocation of the radial head at the proximal radioulnar joint (PRUJ). Bado classified these into four types based on the direction of radial head dislocation. Option B describes a Galeazzi fracture.
Reference: Bado JL. The Monteggia lesion. Clin Orthop Relat Res. 1967;50:71-86.