Fractures of the phalanxes, scaphoid, calcaneous, skull, and those of intra-articular surfaces develop minimal to no callus that is evident on radiography. This is also true for impacted fractures, but is not the case for comminuted fractures or those with wider gaps between the bony fragments. Also, macroscopic vascular injury increases the incidence of delayed union and nonunion. 4 Fracture management also influences the amount of visible callus. The extent of periosteal stripping, the fixation of the fracture, and the amount and timing of weight bearing can be contributing factors to when a callus appears radiographically.
Most investigations focus on the biomolecular process of fracture healing.
Postacchini et al 19 studied long bones in normal adults and found calcification foci histologically by 7 days, and many new trabecular bone were identified by 15 days. Despite the lack of research, some of the review articles and textbooks address the timing regarding radiographic evidence of the callus. In a review, Chapman 12 points out that periosteal new bone or callus can be seen in an infant as early as 4 days after an injury, although 7 to 14 days is more typical. Frost 2 suggests that mineralization in long bone fractures takes at least 4 weeks before being evident on radiographs. Monahan 15 cautions that the exact timing of radiographic examination depends on many variables, which include the nature and location of the fracture along with the patient's age.