What evidence on bone indicates healing after a fracture?

• A. The presence of a callus bridging the fracture line and remodeled bone
• B. Absence of any callus or new bone formation
• C. A smooth surface without irregularities
• D. Complete restoration to original microscopic density

Answer: (A)

Healing after a fracture is shown by the formation of a callus that bridges the fracture line and by subsequent remodeling of the bone. When a bone breaks, the body forms a stabilization callus that spans the gap, first as a soft/cartilaginous tissue and then ossifies into a hard callus across the fracture. This bridging callus demonstrates that the bone ends are being connected and stabilized, a key sign that healing is progressing. Over time, remodeling replaces the temporary woven bone with stronger lamellar bone and smooths the outline, restoring continuity of the cortex.

This is the best evidence because it directly reflects the healing process: the fracture ends are united by new bone and the architecture is being restored. The other options don’t indicate healing as clearly. Absence of callus or new bone formation suggests nonunion. A smooth surface without irregularities isn’t typical during healing, which involves irregular edges and callus before remodeling. Complete restoration to the exact microscopic density is not a guaranteed or sole indicator of healing, even though remodeling may eventually approximate normal density.