Coronoid Fracture
A coronoid fracture is a fracture involving the coronoid process of the ulna, an essential anterior bony prominence of the proximal ulna that contributes significantly to elbow joint stability. These fractures usually occur due to elbow trauma, often in conjunction with elbow dislocations and ligamentous injuries, forming part of complex elbow instability patterns. Accurate diagnosis, classification, and appropriate management—operative or non-operative—is critical to restoring joint stability and function, preventing chronic instability, stiffness, or arthrosis.
Anatomy and Biomechanics
The coronoid process is a triangular, anterior projection from the proximal ulna forming the anterior border of the greater sigmoid notch, which articulates with the trochlea of the distal humerus. Understanding its anatomy and biomechanical role is crucial in managing fractures.
- Bony anatomy: The coronoid process has three important facets:
- Tip: The apex, where the brachialis muscle inserts.
- Anteromedial facet: Medial portion articulating with the medial trochlear ridge, important in varus stability.
- Base/body: The broader proximal segment integrating with the ulnar shaft.
- Articular surface: Forms the anterior articular rim of the greater sigmoid notch that articulates with the trochlea, engaging especially at 90° or more elbow flexion; provides the key anterior bony restraint preventing posterior subluxation or dislocation.