Fractures could be treated by removing bone marrow and injecting a hormone, research has suggested.
The technique has been hailed as a potential way of healing weakened and broken bones without the need for surgery.
A study on rats revealed that after marrow - a spongy material inside the bones that produces stem cells - was removed, new bone formed in the cavity. But while this was short-lived in most of the animals, the new bones continued to grow and become stronger among animals given the drug.
In the study, reported in the New Scientist, Agnes Vignery's team at Yale University anaesthetised a group of rats and drilled into the left thigh-bone of each animal in order to syringe out the marrow. Some of the rats were given daily doses of parathyroid hormone (PTH), which encourages the growth of new bone.
X-rays of the animals taken two weeks later showed that new bone had begun to form in the space previously filled by the marrow. By the third week, marrow began to reappear in most of the rats and any new bone cells were absorbed to make room for the marrow.
But this did not happen in the rats treated with PTH, with new bone continuing to grow into the third week and no sign of marrow reappearing. The team also discovered that the de-marrowed thighbones of PTH rats were stronger than their other legs, and the legs of rats not given the hormone.
Bone marrow stem cells are needed to produce blood cells but Dr Vignery said people's health should not be affected by the removal of marrow in one bone as long as it remains in other bones.
Warren Levy of New Jersey-based Unigene Laboratories, which provided the PTH for the study, said the procedure could lead to major changes in the way patients are treated, by offering an alternative to major surgery which is expensive and can be life-threatening for the elderly.
"If an X-ray reveals a fracture, you could go in with a needle right there in the doctor's suite and do without surgery," he said. The patient would then be sent home with a prescription for PTH, and the fracture would repair itself from the inside.
Further animal tests are needed but it is hoped the technique could be tested on humans before the end of the year, Mr Levy added.