Haptic feedback

A virtual reality device which allows surgeons to feel they are touching realistic forces when touching surfaces such as bone and cartilage could help them train for intricate operations.

The haptics system, being developed at ImperialCollege, is designed for complicated ‘keyhole’ procedures such as knee arthroscopy.

Surgeons carrying out this operation have restricted vision and movement, and as a result the procedure requires extensive practice, said Edward Dibble, a researcher at the university’s mechatronics in medicine laboratory.

The system is based on the use of strain gauges to sense forces, and motors to provide a feedback of torque. A specially-developed haptic rendering algorithm tracks the tip of the device and checks for collisions between the surgeon’s probe and the virtual bone models, and then calculates the correct force to provide an accurate simulation of the contact with the surface, said Dibble.

‘The contact is modelled as a virtual spring, such that a small penetration depth is needed to generate a force. Our device delivers significantly higher forces and stiffness than existing devices and surgeons who have tried it say it feels authentic,’ he said.

The researchers now hope to get funding to further develop the device, in particular to shrink it down to to fit inside an artificial leg, said Dibble. ‘We would like to shrink the hardware such that it can fit inside a model knee which would provide unparalleled realism, allowing the surgeon to manipulate the knee.’

A number of models representing different surgical procedures could be added to the system, which could be used to provide an assessment of the trainee surgeon’s skills, and log any mistakes.

Unlike physical models used for surgery practice, the system can also be programmed to represent the fluid around areas such as the knee, providing a more realistic experience.

Physical models also have to be replaced regularly, according to Dr Alex Zivanovic, research associate at the laboratory. ‘Surgeons definitely think virtual reality is the way forward,’ he said.

Building a commercial system is expected to take another two years.