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Growing use of synthetic bone for surgery
EVERY day, orthopaedic surgeons use bone from a bone bank, or from a patient’s own body, during a range of procedures. For example, spinal fusion involves bringing vertebra together to produce a bond; complex fractures involve replacing bone fragments; lesions in bone caused by cancer need filling, and revision hip procedures require a packing out of the boney space by impaction grafting.
Currently, this demand is satisfied mainly by the use of real bone (autograft) from the patient’s body but this approach causes additional pain and surgical complexity; or from a bone bank (allograft) which runs the risk of transmitting infection. For both autografts and allografts the amount of natural material available may be limited.
At Cambridge University, eastern England, Professor Bill Bonfield heads the Cambridge Centre for Medical Materials which is aiming to replace bone with materials developed in the laboratory. “My vision,” he says, “is to make available a range of synthetic materials which reproduce all the characteristics of natural bone and would be readily available to facilitate the operation.”
Already, Professor Bonfield has produced a replacement material for the bones of the middle ear that transmit sound and allow a patient to hear. The clinical success has been outstanding because of the ability of the surgeon to precisely fit the middle ear space which is individual to each patient.
The professor innovated a bone replacement material - called Hapex - which seduced real bone into thinking it was the same material and hence produced a bond between the implant and the adjacent tissue. The material can be cut and shaped with a scalpel by the surgeon in the operating theatre, to obtain the best possible fit.
One of Professor Bonfield’s projects involves the development of a porous material, based on a calcium phosphate which in its porous form acts as a precursor and allows the regeneration of bone as a direct replacement of itself. This material is now being exploited commercially via a new company, ApaTech. The company has already taken the process into various pilot clinical trials.
The Cambridge Centre for Medical Materials has a number of such projects that have potential, within a decade, to alter the whole approach to reconstructive medicine. Not only will existing techniques be enhanced but there are exciting opportunities to engineer other tissues and organs. — Dawn/LPS feature
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