Over the past several years, there have been inevitable bone fractures: People slip on ice, for instance, and fracture a wrist or elbow. Or miss a step and fracture a foot, fall off a ladder and fracture a leg.
People will come to my office and tell me that their orthopedist commented that they healed faster than usual, often faster than anyone else they've seen before. My son was told this after he shattered his hand getting slammed against the boards in hockey; his orthopedist took the screws and cast off much sooner than usual since he judged that healing had occured early. (My son was taking 8000 units vitamin D in gelcap form; I also had him take 20,000 units for several days early after his injury to be absolutely sure he had sufficient levels.)
My suspicion is that people taking vitamin D sufficient to enjoy desirable blood levels (I aim for a 25-hydroxy vitamin D level of 60-70 ng/ml) heal fractures much faster, abbreviating healing time (crudely estimated) by at least 30%.
For any interested orthopedist, it would be an easy clinical study: Enroll people with traumatic fractures, randomize to vitamin D at, say, 10,000 units per day vs. placebo, watch who heals faster gauged by, for instance, x-ray. My prediction: Vitamin D will win hands down with faster healing and perhaps more assured fusion of the fracture site.