Marrow loss 'aids bone healing'

Removing the marrow from the heart of bones could make them stronger and help heal fractures, researchers suggest. Even though the marrow is rich in stem cells which help repair bones, rats treated using the technique were found to recover more quickly.

The Yale University experiment could help older patients avoid major surgery such as hip replacement, the report in New Scientist says. A UK orthopaedic surgeon said that the idea might have "potential".

Many of the large bones in the human body have a cavity where bone marrow - which produces new blood cells -collects. The Yale team, led by Agnes Vignery, drilled into the upper leg bone of anaesthetised rats, and removed the marrow. Some rats were treated with a hormone which encourages the growth of new bone, and both groups were X-rayed to see how their bones recovered.

At first, both sets of rats began to lay down new bone material in the space formerly occupied by the marrow, at the centre of the bone. In the rats who did not have extra hormone treatment, this bone disappeared within weeks and the marrow returned in its place. However, in those given the drug, called PTH, the bone continued to grow, and the marrow did not come back.

This meant that the overall strength of the PTH-treated bones was stronger even than their owner's, completely unaffected, leg. The researchers said that the technique could offer rapid growth of new bone in areas weakened by bone loss.

They said that the loss of some bone marrow should not compromise the ability to make enough blood cells.

If reproduced in humans, it could offer the potential for a simple procedure using a needle to remove the bone marrow in a fractured bone rather than a more complex operation.

Dr Brendan Noble, from the University of Edinburgh, said that the loss of bone stem cells seemed "counter-intuitive" at first, but it was possible that other types of cells, including those in the membranes surrounding the bones, were involved in the recovery. "Perhaps they are sufficient to take on the role," he said.

Peter Kay, a consultant orthopaedic surgeon at the Wrightington Hospital in Wigan, said that the idea of removing marrow with a needle rather than performing a major operation to fix a fracture was promising. He said: "This sort of minimally invasive technique to replace surgery sounds controversial, but if you strengthen rat's bones maybe there is potential."