Body wall force sensor for simulated minimally invasive surgery: Application to fetal surgery

Surgical interventions are increasingly executed minimal invasively. Surgeons insert instruments through tiny incisions in the body and pivot slender instruments to treat organs or tissue below the surface. While a blessing for patients, surgeons need to pay extra attention to overcome the fulcrum effect, reduced haptic feedback and deal with lost hand-eye coordination. The mental load makes it difficult to pay sufficient attention to the forces that are exerted on the body wall. In delicate procedures such as fetal surgery, this might be problematic as irreparable damage could cause premature delivery. As a first attempt to quantify the interaction forces applied on the patient's body wall, a novel 6 degrees of freedom force sensor was developed for an ex-vivo set up. The performance of the sensor was characterised. User experiments were conducted by 3 clinicians on a set up simulating a fetal surgical intervention. During these simulated interventions, the interaction forces were recorded and analysed when a normal instrument was employed. These results were compared with a session where a flexible instrument under haptic guidance was used. The conducted experiments resulted in interesting insights in the interaction forces and stresses that develop during such difficult surgical intervention. The results also implicated that haptic guidance schemes and the use of flexible instruments rather than rigid ones could have a significant impact on the stresses that occur at the body wall.