This mechanism is more commonly seen in elderly patients. This “breaking the fall” reaction leads to breaking the bone: an avulsion fracture of the tip of the olecranon, pulled off by the triceps. If there is a fall on a semi-flexed arm, when the hand strikes the ground, the triceps muscle forcefully contracts, resisting further flexion of the elbow. The mechanism of injury often determines the fracture pattern. (V arus /valgus instability is rarely encountered and pain may impede its detection anyway.) The primary determination to be made on exam is whether the extensor mechanism is intact. Patients with fractures of the olecranon present with elbow pain after direct elbow trauma or fall.
The flexor carpi ulnaris originates (in part) from the medial border of the olecranon. The proximity if the ulnar nerve to the olecranon makes it vulnerable to injury when fractures occur. The ulnar nerve runs on the posterior aspect of the elbow, behind the medial epicondyle of the humerus it then turns anteriorly joining the ulnar artery. The lateral border of the olecranon is the attachment point for the anconeus muscle. This fibrous covering prevents fractures from being dramatically displaced unless the force is so great that the soft tissues are ruptured along with fracture of the bone. Its fibers blend with the periostium of the olecranon, the lateral ligaments and the articular capsule, forming a strong fibrous covering. The triceps muscle inserts into the proximal ulna and posterior third of the olecranon. The olecranon is an important secondary stabilizer too: it inhibits anterior translation of the ulna with respect to the distal humerus just as the coronoid process of the ulna resists posterior subluxation of the ulna. The main side-to-side (valgus and varus) stabilizers of the elbow are the collateral ligaments and the ulnohumeral/radiohumeral articulation, which provide a buttress againstulnar or radial compressive forces laterally. Successful treatment of olecranon fractures requires not only re-establishment of the extensor mechanism (which would be disrupted if/when a fracture displaces) but also preservation of elbow stability. The trochlear notch is covered with articular cartilage, therefore most olecranon fractures (except the ones occurring exclusively on the tip) are, by definition, intra-articular fractures. This notch holds the trochlea of the distal humerus forming the ulnohumeral articulation, the hinge joint of the elbow. The olecranon is a strong process of the proximal and posterior ulna that, together with the coronoid process, forms the trochlear notch. Figure: Radiograph of displaced fracture.
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