Distal radial fractures heal by direct woven bone formation

BACKGROUND Descriptions of fracture healing almost exclusively deal with shaft fractures and they often emphasize endochondral bone formation. In reality, most fractures occur in metaphyseal cancellous bone. Apart from a study of vertebral fractures, we have not found any histological description of cancellous bone healing in humans. PATIENTS AND METHODS We studied histological biopsies from the central part of 12 distal radial fractures obtained during surgery 6-28 days after the injury, using routine hematoxylin and eosin staining. RESULTS New bone formation was seen in 6 cases. It was always in the form of fetal-like, disorganized woven bone. It seldom had contact with old trabeculae and appeared to have formed directly in the marrow. Cartilage was scarce or absent. The samples without bone formation showed only necrosis, scar, or old cancellous bone. INTERPRETATION The histology suggests that cells in the midst of the marrow respond to the trauma by direct formation of bone, independently of trabecular surfaces.