Touching Lives - November 2005
How it was discovered
Artificial bones that grow!
Until recently, doctors treating patients with bone cancer only had one option — to amputate the affected limb. Despite the significant physical and psychological implications for the patient, amputation was the only way to stop the cancer spreading.
Eventually, metal implants were developed to replace the cancerous bone and save the limb. For adults this was an ideal solution, but for children, whose bones are still growing, the implants solved only half the problem.
The implants needed to be extendable to keep up with the child’s natural rate of growth. ^Extendable implants were available, but making them ‘grow’ required large incisions^, and the sudden lengthening sometimes caused painful damage to the tissues around the implant. These regular lengthy hospital stays and subsequent weeks of recovery were very disruptive for the child and their family.
But Action Medical Research was on the case. For many years the Charity had supported the work of John Scales, Professor of Biomedical Engineering at the Royal National Orthopaedic Hospital in Stanmore. His team had been working hard to improve the quality of bone implants for patients, and in 1990 he was awarded funding to design an implant that required no surgical intervention at all.
A ‘growing’ prosthesis
The team began by improving the design of the existing implants so that the procedure for extending them was far less invasive. By adapting the extension mechanism, they made it possible to adjust the length using key-hole surgery, which required a much smaller incision in the limb and far less time in hospital. These modified implants swiftly became a routine part of treatment at ##Artificial bones that grow!bone tumour centres across the UK, immediately improving care for young bone cancer patients.
However, the Holy Grail for the team, now lead by Professor Peter Walker after John Scales’ retirement, was to devise an implant that could be manipulated without the need for any invasive surgery at all, and they achieved this using a design that relied on magnetic force. This revolutionary implant contained a telescopic section controlled by a screw and miniature gear box. ^A special tube was placed around the patient’s leg which created a strong enough magnetic force to turn the screw and extend the implant.^ This technique meant an end to painful and invasive surgery, and it mimicked far more closely the natural growth-rate of children’s bones.
The device was first implanted in a patient in 2002 and is now coming into routine clinical use both in the UK and abroad.
**Thank you to the BUPA Medical Foundation Ltd for kindly supporting this research.