"Everyone told us this was a crazy idea," says Tony Mulligan of Advanced Ceramics Research (ACR), Inc., Tucson, AZ. "Only the Office of Naval Research said they'd take the chance. That was just five years ago."
When an arm or a leg bone is severely crushed, physicians usually cannot set it and bone grafts, or amputation — until now — has remained the primary option. The same is true for bones damaged by disease, such as cancer.
Mulligan's company has invented a process that may change all that. If, for instance, the humerus bone in the arm is injured and damaged, ACR has shown that a cat scan or MRI image can be made of the good arm bone, and converted to a "growth code" — a 3-D virtual image — of the replacement bone segment needed. Using that data, ACR's rapid prototyping technology then creates a micro-porous calcium phosphate coated polymer ‘bone' which is then surgically implanted into the arm where the damaged bone has been removed. The calcium phosphate coating is very thin and allows the bone cells to attach themselves to the implant. Growth factors could be added to the calcium phosphate to encourage the bone growth at faster rates.
"What is left of the real bone attaches itself to the polymer bone after about 8 weeks," says Dr. Ranji Vaidyanathan of ACR, inventor of the process. "Then, the real bone begins to ‘grow through' the porous scaffold. As it does, it ‘eats' the scaffold, and the body naturally excretes the calcium phosphate material. In 18 months, the expectation is that the bone will grow back completely, leaving the patient with natural bone." Proof that the process works has been shown in animal testing as well as in tissue cultures.
This project is funded by the Navy Small Business Technology Transition (STTR) program in the Office of Naval Research, but the work ONR did in manufacturing research motivated the topic, according to Ralph Wachter, ONR science manager. ONR had been focusing on rapid producibility of fully-dense parts from metals and from ceramics for defense needs but decided to look for new application areas and materials. ONR also wanted to address issues where customization and controlled porosity were objectives. "We decided on the dual-use area of bioengineering and tissue engineering in Navy's STTR program." says John Williams, Program Officer for this work at ONR.
"ACR has taken technologies originally developed for the rapid prototyping of military parts and transitioned them into applications that will have wide spread use across the medical community. The process, once tested and proven in military scenarios, would transition rapidly to the public."