System used to describe olecranon fractures. Type 1a Ð nondisplaced, noncomminuted; type 1b Ð nondisplaced, comminuted; type 2a Ð displaced non-comminuted; type 2b Ð displaced and comminuted (but stable); type 3a Ð unstable, noncomminuted; type 3b Ð unstable, comminuted.