12A1   Simple fracture, spiral

Simple spiral fractures of the humeral shaft are classified as 12A1 fractures.

There are only two fragments, and the fracture plane is a spiral, caused by a twisting force on the shaft of the humerus.

This fracture type is subdivided:

• 12A1(a) - Proximal 1/3
• 12A1(b) - Middle 1/3
• 12A1(c) - Distal 1/3

In fractures located in the proximal zone of the diaphysis (12A1(a)), note that the deltoid muscle predominates and may interfere with treatment.

In fractures located in the distal third of the humerus (12A1(c)), the radial nerve is at risk more even than in the other regions.

Image taken from Orozco R, et al. Atlas of Internal Fixation. Paris: Masson; 1998. Used with kind permission.