Capitellum Fracture Classifications
The Bryan and Morrey classification system is the primary system used to categorize capitellum fractures, with Type I (Hahn-Steinthal) representing isolated capitellar shearing fractures and Type IV representing complex fractures involving the capitellum, trochlea, and lateral epicondyle. 1, 2
Bryan and Morrey Classification System
The classification distinguishes fracture patterns based on the extent of articular involvement and associated structural damage:
Type I (Hahn-Steinthal Fractures)
- Isolated capitellar fractures involving a large, single osteochondral fragment sheared in the coronal plane 1, 3
- These represent the classic "isolated" capitellum fracture pattern, though modern imaging often reveals more complexity than initially apparent 4
Type IV Fractures
- Complex fractures involving the capitellum, lateral trochlear ridge, and significant portions of the trochlea 2, 5
- May include three-part variants with Y-shaped splits of the distal humerus, featuring both anterior articular fragments and large posterolateral non-articular fragments 2
- Can present with associated posterolateral rotational instability requiring additional fixation beyond standard capitellar repair 2
McKee Classification Extension
A more recent classification system by McKee has been proposed to capture additional complexity:
McKee Type 4
- Osteochondral shearing fractures encompassing the capitellum with significant lateral trochlear ridge and trochlear involvement 5
- These fractures may be associated with soft tissue injuries including distal triceps tendon avulsion 5
Proposed McKee Type 5
- Complete coronal plane fractures where the entire capitellum and trochlea are fractured as a single unit, potentially with associated distal triceps tendon avulsion 5
Dubberley Classification System
An alternative system stratifies fractures by complexity:
Type 1
- Simple fracture patterns with better functional outcomes 4
Type 3
- Complex fracture patterns with significantly worse functional results compared to Type 1 4
Critical Clinical Recognition
The majority of apparent "isolated" capitellar fractures are actually complex fractures involving both the capitellum and trochlea, requiring careful preoperative imaging assessment 4. A well-taken lateral radiograph is essential for proper classification, though CT or MRI may be necessary to fully characterize the injury pattern 1, 4.
Associated injuries occur frequently and must be systematically evaluated: