Surgical treatment for posterior distal humeral shear fractures

Posterior shear fractures of the distal humerus are rare and have a complex, controversial injury mechanism. This study aims to investigate the morphological characteristics, injury mechanisms, and treatment outcomes of these fractures. From March 2021 to October 2024, 13 patients with posterior shear fractures of the distal humerus were treated with open reduction and internal fixation. Among them, 7 were male and 6 were female, with a mean age of 40 years (range: 25-66 years). Five cases involved the left side, and 8 involved the right side. All fractures were closed. Most cases (n = 12) were posterior capitellar shear fractures, with only 1 case of posterior trochlear shear fracture. Ten cases were caused by valgus posterolateral rotational injury, and 3 were caused by varus posteromedial rotational injury. A lateral approach was used in most cases (n = 9), followed by a combined medial and lateral approach (n = 4), with the medial side addressed via an over-the-top approach. Fractures were fixed using anchor screws, Herbert screws, coronoid plates, and Kirschner wires. All the patients were evaluated using the Mayo Elbow Performance Score during the follow-up. All patients were followed up for a mean of 25 months (range: 12-38 months). The mean fracture healing time was 12 ± 2 weeks. Postoperative complications included degenerative osteoarthritis of the elbow (n = 1), heterotopic ossification (n = 1), and ulnar neuropathy symptoms (n = 1). At the final follow-up, the mean elbow flexion-extension arc was 127° ± 13°, the forearm rotation arc was 173° ± 5°, and the Mayo Elbow Performance Score was 95 ± 5 points. Results were rated as excellent (n = 12) and good (n = 1), with an excellent-to-good rate of 100%. Posterior shear fractures of the distal humerus mostly involve the posterior of the capitellum and are often associated with elbow dislocation. These fractures are primarily caused by valgus posterolateral rotational injury force. Surgical management should therefore include the repair of both the fracture and the stabilizing ligamentous structures.