Force-torque Measurement System for Fracture Surgery

Many surgical procedures are now performed using the techniques of minimally invasive surgery (MIS), in which the surgeon manipulates instruments inserted into the patients through small incisions. In MIS, the surgeon has no direct contact with internal body parts. Applying an optimal force and torque via the instruments is necessary to conduct an operation without causing any damage to the internal tissue. Most studies have so far been reported for general MIS where force-feedback is added to laparoscopic instruments using various sensing technologies (Menciassi 2001), (Song 2011). This paper reports our work on minimally invasive fracture surgery, where the issue of force feedback is as important and relates to the manual manipulation of externally fixated pins inserted in the fracture fragments to reduce the displacements. The related work in this field includes developments of surgical robots for fracture reduction of femur. Some of these robots e.g. (Douke 2008), (Gösling 2006) are equipped with the force measuring sensors to compensate for the inaccuracy of bone motion caused by surrounding ligaments and muscles. Forces and torques have been measured and reported in phantoms (Douke 2008) and in patients during femur fracture reduction (Gösling 2006). Our study is focusing on robot-assisted reduction of fractures that include joints (Raabe, 2012). The surgical procedure of this type of fractures involves moving individual fragments to the correct anatomical position. The forces required to execute these manoeuvres have to be established in order to design robot controllers and safety parameters for the system. The measurements will be recorded during manual displacement of the bone fragments using a periosteal elevator (orthopaedic instrument used to handle periosteum and bone fragments during a fracture surgery) on patients’ legs subjected to these forces. For this purpose we have created a modified instrument that can be used in real surgeries.