06/2 Intelligent surgical instruments in spinal surgeries

		Prototype of an instrumented distraction device Design concept of a high pressure cement injection device

There is a distinct trend towards less and minimally invasive approaches in orthopaedics. These techniques systematically reduce the exposure to the surgical object and thus aim at minimising surgical trauma. However, orientation during associated surgical actions, such as bone cuts, reposition procedures, screws placements, etc. becomes more and more difficult especially for the less experienced surgeon. Current surgical instruments are typically pure mechanical devices which are rarely equipped with intelligent sensor systems. Important biomechanical information like forces, moments and displacements cannot be provided to the surgeon.

Monitoring loads in sensor-equipped smart instruments and surgical implants, fixation and distractor devices will be valuable to ensure optimal insertion during implant fixation, to monitor fracture stabilisation and healing, to evaluate rehabilitation exercises, to prevent dangerous overloads and material fatigue and improve the design of new implants. Both integrated microsensors with embedded wireless telemetry circuits as well as wireless active and passive micro-strain sensor solutions will be part of this project. The focus is on improvements of treatment strategies in the lumbar and thoracic spine and related back pain treatment strategies.

The following devices will be developed:

Instrumented distraction forceps

In order to treat spinal deformities such as scoliosis, mechanical distraction and immobilisation techniques are used. Some of them utilise distraction forceps to correct or adjust the spatial position of adjacent vertebrae. Currently no objective assessment about the distraction forces and distances exist. The instrumentation of a distraction forceps with appropriate sensor technique will allow for the first time an objective quantification of intraoperatively applied distraction forces and achieved distraction length and thus bring additional reliability to these interventions.

High pressure cement injection system

In vertebroplasty and the similar kyphoplasty (minimally invasive procedures to relieve pain of compression fractures), highly viscous cements are injected into a collapsed vertebral body to stabilise a fracture and reduce pain. Most severe complications in vertebroplasty result from cement leakage into the patient's venous system, which can cause thrombosis. Recent experiments suggest that the risk of cement leakage is greatly reduced when the material is injected in a high-viscous state, but this requires high injection pressure. When using traditional syringes for injecting cement, forces up to 200 N are exerted by the operator's thumb resulting in pressures up to 1.5 MPa. With screw-type systems, pressures up to 4 MPa can be generated but the tactile sensory feedback is lost. We aim at developing a computer-assisted high-pressure injection device for highly viscous materials that combines the advantages of manual high-pressure systems with the benefits of traditional syringes and offers control over injection parameters such as volume, pressure, injection rate and viscosity.