The hip gets smart

Materials World magazine
1 Apr 2010

Wirelessly monitoring and improving the real-time performance of bone implants is the goal of a project at the University of Porto, Portugal.

The ‘Smart hip’ concept is for a traditional rigid implant to incorporate miniaturised sensors that transmit information regarding problems to doctors. It also stimulates bone growth using piezoelectric actuators, improving quality of life and reducing the need for surgical intervention. The proof-of-concept is said to have been validated in animal tests with results still to be published.

‘Most of the components are inside the device, [therefore] isolated from the organism with biomaterial that is biocompatible,’ explains Clara Frias, the PhD student who developed the concept.

The actuators that are placed on the implant’s surface are made from biocompatible polyvinylidene fluoride (PVDF) piezoelectric materials, which stimulate bone growth by mechanical simulation of the osteoblast cells. The films are printed with silver ink electrodes and then coated with poly (methyl methacrylate) and microparticles of Bonelike, a patented glass reinforced-hydroxyapatite. The coating is designed to ensure osteoblast adhesion to the device surface and electric insulation.

The team demonstrated the concept by growing osteoblasts on the coated PVDF’s surface in static and dynamic conditions, and measuring total protein, cell viability and nitric oxide levels. Work is ongoing.

Frias claims that using PVDF means that control of the mechanical ranges simulation is only dependent on the amount of electrical energy applied, and that the bone could be stimulated in different directions by changing the piezoelectric constants. She adds, ‘The smart structure concept can be adapted to other active devices’.

Dr Darren Wilson, Project Leader Smart Implants, at Smith & Nephew’s research centre in Heslington, UK, says the idea of using piezoelectric materials locally from an implant in this way is not new. Getting it to work in clinical practice, however, is a challenge.

‘It is clear that smart implants are a potential competitor threat to orthopaedics, however, issues relating to cost, reimbursement, regulatory approval, and performance need to be addressed before they become commercial entities and are routinely used. It would be interesting to see the results of the animal study when they materialise.’

He adds, ‘Smart implants that can sense and respond to their environment in a controlled beneficial fashion will have major benefits in an era where bone and joint management is continually changing to meet the needs of an aging and active population that expects to maintain function and mobility’.