The feasibility, development, and accuracy of a re-instrumented force sensing retracting suction neurosurgical tool

This thesis investigates the feasibility, development, and accuracy of implementing two inline sets of uniaxial strain gauges for a neurosurgical force sensing suction and retraction (FSSR) instrument to determine force metrics such as magnitude, location, and orientation of applied force in real time. Excess force applied during a neurosurgery could lead to complications for the patient during and after surgery, thus there is clinical need for a quantitative real time tool-tissue feedback for various surgical tools. A force-based metric has been observed to be highly correlated to improving not only surgical training but also the outcome of surgical procedures. Past literature and previous studies attempted to design a force sensing retractor. Although previous investigations and prototypes have developed methods and protocols to detect small magnitude forces applied, they lacked the ability to detect the magnitude of force without knowing the distance of the applied force. This is a critical limitation because the location of a net applied force can vary along a retractor during surgery and is often unseen and cannot be measured during surgery. The main goal of this current investigation is to modify the previous design of the force sensing suction retractor (FSSR) device with a new placement of strain gauges, utilizing a novel configuration of an aligned pair of strain gauge arrangement with only knowing the distance between the pair of gauge sets and the strain data collected. The FSSR was a stainless steel suction tube retrofitted with 8 gauges: two sets of 4 gauges aligned and separated radially by 90 degrees within each set. Calibrations test and blind load tests were conducted to determine accuracy of the instrument for detecting the force metrics. It was found that a majority of 40 variations for the calibration tests maintained a percent difference under 10% when comparing actual and calculated values. Specifically, using calibration test 2 for blind test 2 the orientation yielded a calculated value that was 2.1 degrees different. Blind test 2 for the magnitude yielded a calculated value that was .135 N different, which is a 9.104 % difference. Also, blind test 2 set 1 and set 2 for the location of applied load from set 1 and set 2 yielded a calculated value that was 7.334 mm different, which is an 8.95 % difference for set 1 and a 15.63 % difference for set 2. Possible limitations and errors in the protocol that may have increased the discrepancy between actual and calculated values include how accurate the strain gauges were placed in terms of both alignment and radial orientation. Future work in regards to improving the new FSSR prototype, is to first develop a better method to ensure accurate placement of gauges, both in paired alignment between sets and radial separation within sets. Overall, the clinical considerations for a force sensing tool is aimed at minimizing patient injury during surgery, devices such as the force sensing suction retractor is an example of novel technology that could become a standard technology within the operating room.