Left: “Fresh” subperiosteal hemorrhage, as seen in x-ray of 9-month old infant. Right: Result of subperiosteal hemorrhage, as seen in femur split down the anteroposterior plane. Fracture can be seen about a quarter-length down from the head, displacing the epiphysis (the rounded head of the femur that is supposed to articulate with the hip). There is a large separation of the periosteum from the upper half of the bone, with new bone formed between the shaft and periosteum, due to a pre-existing subperiosteal hemorrhage.
In scurvy, creation of collagen and capillaries (which rely heavily on ascorbic acid, aka vitamin C) are both impaired, leading to poor wound healing, fragile capillaries and capillary beds (such as in the periosteum, which supplies nutrients to the bones), and structurally unsound bone growth. When these are combined, fractures and subperiosteal hemorrhages are inevitable, and in children, this leads to great bone deformation that affects them for the rest of their lives.
While adults may suffer many of the same symptoms of scurvy, the fact that their bones already have the support structure and are slow-growing in general, means that they’re at a much lower risk for subperiosteal hemorrhage causing extraneous bone growth. Though adult bones are weakened, that generally leads to breaks straight through the shaft, rather than internal fractures.
Diseases of Infancy and Childhood. Louis Fischer, 1917.