Epiphysis of humerus

There are three epiphyses at the upper end of the humerus, namely the humeral head, large nodules, and small nodules. The epiphysis appears at the age of 1, 3, and 5 years old. The three epiphyses merge at 5 to 8 years old to form an epiphysis at the upper end of the humerus. Aged epiphysis fused with humerus shaft. Therefore, the epiphyseal separation of the upper humerus is more common in 7 to 18 years old; humeral anatomical neck fractures can occur in adults in the future. Because the upper end of the humerus is on the frontal plane, the metaphysis of the humerus forms a sloping angle of about 15 °, and the center of the epiphysis is located on the medial and posterior side of the epiphyseal plate. Therefore, the violent force transmitted upward along the humeral axis acts on the epiphyseal plate, generating shear stress The fracture line is oblique, the anterolateral part is separated by the epiphyseal surface of the epiphyseal plate, and the posterior medial part passes through the metaphysis, forming a triangular bone fragment. The slope of the fracture line varies with age. The older the fracture line passes through the epiphyseal plate The shorter the transverse distance, the larger the metaphyseal fracture fragment, and the longer the slope distance, the more unstable the fracture end.