A bone loss of several centimeters cannot be spontaneously regenerated. It can be:
The most common type of bone loss is osteoporosis. Osteoporosis causes an excessive fragility of the skeleton. It is due to a reduction in the amount of bone mass and a deterioration of the microarchitecture of the bone.
For instance, a cavity left after the excision of a tumor.
When a segment of bone is lacking: for example after a fracture of the shaft of a long bone (diaphysis) with tissue loss in a limb, or when a bone flap in the skull is lost.