Operative Management of a Late-Presenting McKee Type IV Capitellum Coronal Shear Fracture via an Anterolateral Approach: A Rare Case Report.

Introduction: Coronal shear fractures of the distal humerus are rare, comprising <1% of elbow fractures. McKee Type IV fractures involve both the capitellum and lateral trochlea. These injuries are uncommon and may result in stiffness and functional impairment if diagnosis is delayed or treated conservatively. Case Report: A 15-year-old boy presented 6 months after an untreated McKee Type IV coronal shear fracture of the distal humerus with pain, stiffness, and restricted elbow motion. Radiographs and computed tomography demonstrated a malunited shear fragment with a "double-arc" sign. Osteotomy through the malunited fracture plane was performed through an anterolateral approach, followed by fixation with headless compression screws. Early mobilization was initiated postoperatively. At 18 months, the patient achieved a flexion-extension arc of 0°-120°, full forearm rotation, and radiological union. The Mayo Elbow performance score was 95, and the disabilities of the arm, shoulder, and hand score was 4.2, indicating excellent functional recovery with minimal disability. No radiographic signs of avascular necrosis were noted. Conclusion: Osteotomy-assisted open reduction through an anterolateral approach appears to be a viable surgical option for late-presenting McKee Type IV coronal shear malunions, enabling restoration of joint anatomy and function. However, conclusions are limited by the single-case design, absence of comparative analysis, and lack of long-term follow-up.