bones from old
Medical researchers have discovered how to build a ‘scaffolding’ in the human body for the repair of worn or damaged bones, writes Elisabeth Lickindorf
South African scientists have published dramatic findings that could one day enable patients to order custom-designed spare parts to help their bodies regrow bones that get damaged or wear thin.
Cutting-edge work – which could perfect the procedures by which damaged limbs are surgically removed and new ones inserted – is revealed in three research papers in the latest South African Journal of Science.
Professor Ugo Ripamonti, who heads the Medical Research Council/University of the Witwatersrand bone research unit, has demonstrated that given the right piece of artificial “scaffolding”, the body can actually be persuaded to regrow its own bone around it. Members of the Council for Scientific Industrial Research’s (CSIR) manufacturing and materials technology team have worked with him to design and manufacture a synthetic, porous bioceramic – looking a little like a pumice stone – suitable for constructing that scaffolding.
This remarkable collaboration is a triumph for South African science and could give a pain-free lease of life to road accident victims and people suffering the devastating effects of brittle bones. Ripamonti himself recently and miraculously recovered from a motorbike accident that tore his body apart and put him into a coma for weeks.
Successful implants depend heavily on their design, on the surgeon’s skill, and on the age and anatomy of the patient. The work of Ripamonti and his colleagues could go far in reducing risks and perfecting procedures.
The goal is to replace “off-the-shelf” artificial joints with custom-designed bone implants. This would not only allow artificial inserts to carry weight and stress where the body’s natural bone has deteriorated, but also induce that body to produce its own new bone and tissue to replace the old.
“You must understand the basics of bone formation,” he explains, “and the recent discovery that our cartilage and bone growth is regulated by a family of proteins we never knew about before called BMPs [bone morphogenetic proteins]. Ideally, when we replace a piece of bone that has deteriorated, we’d like another piece exactly the same shape and size as the original to fit the patient’s body precisely.
“We also want the replacement to encourage the body’s own BMPs – rather than BMPs imported into the body from outside – to cling to it and form natural bone growth within and around it. This is what our research is about.”
Ripamonti’s findings pinpoint the precise structure and geometry of the “scaffolding” implant around which bone can be persuaded to grow in the living body.
The companion papers by his CSIR colleagues describe the material they have designed for the scaffolding, and the methods that will one day, it is hoped, enable each patient to get his or her own, unique, perfectly fitting, affordable bone replacement implant.
Here’s how it works. To grow bone the way we want it to grow, an implant needs three things. First, it must supply insoluble scaffolding to give new bone growth the right shape and size. Second, it must be made from biomaterial that can actively induce bone to form by giving out the right signals to the body around it. Third, it must be inserted into a living “host” body able to react to these signals by manufacturing new bone and using its own BMPs to do the job.
Ripamonti, with co-authors J Crooks and AN Kirkbride, announces the extraordinary fact that it’s not just the composition of the implant but also its surface geometric design that makes it suitable. Concave hollows encourage bone and marrow to grow, while convex or hump-like geometry does not.
In as little as 30 days, newly formed bone can bond with an artificial implant, anchoring itself into its pores and concavities, and in 90 days there can be substantial bone formation on the surfaces, with the spaces in the implant penetrated by dense fibrovascular tissue.
The next step is to understand why such growth happens, and how to design the surface geometry of implants so that growth can be predicted and engineered to individual patients’ specifications.
Constructing the right implant was the research problem facing CSIR team members. It had to be friendly to bone growth, light, strong, synthetic, and easy to construct and mould.
Answers lay in the field of bioceramics, where mineral substances are cooked at high temperatures to create ceramics that repair and reconstruct diseased, damaged or worn-out parts of the body.
When Ripamonti asked for his implant, the request was no simple one. The CSIR’s Dr Michael Thomas explains: “Making a ceramic is easy; making a ceramic that’s porous is more difficult; making a ceramic that does the job is most difficult of all!”
Ripamonti has high hopes. “Clinical applications have the potential to save so much complicated surgery – and so much pain,” he adds with feeling. “It needs developing locally and affordably for Africa.”
What drives researchers to breakthroughs that offer such promise for humanity’s wellbeing?
Ripamonti unashamedly loves discovering, creating and developing things for their own sake. “If those things are useful to humankind I’m pleased, but that’s not the primary reason I’ll work in the lab all night!”
For the CSIR’s Dr Willie du Preez, the magic lies in the possibility of actually being able to make something that only the body could make before – something really useful.
Michael Thomas, on the other hand, says he’s “the type who enjoys fixing things – and there’s something mystical about developing synthetic ceramics that can actually help to fix a human being who can do such mysterious things as think and feel.”
The three research papers appear in the August 1999 issue of the South African Journal of Science