Development of a Medical Grinding Tool Considering Material Properties of Wet Bone for Minimally Invasive Surgery

Abstract

Recently, demand for minimally invasive surgery has rapidly increased, especially in the spinal surgery. Surgical resections of spinal column, namely, backbone are frequently conducted using a diamond grinding stone and a high-speed spindle tool in the surgery. The resections have often brought serious nerve root heat injury, because high heat is generated in grinding point close to the nerve root. To address this issue, many studies such as investigations of machining characteristics of bone have been conducted, and various medical technologies and devices such as a coolant supply method have been proposed and developed. However, requirement for suppressing the heat injury in the spinal surgery has currently exceeded the capabilities of the above technologies and devices. To overcome this problem, grinding experiments on bone were performed using commercial diamond grinding tools for clarifying the grinding characteristics. Based on the results that clogging on the tool surfaces is a dominant issue of generating high heat in wet grinding, diamond grinding tools coated by titanium oxide were developed in the hopes of decreasing the clogging by improving hydrophilic property of the tool surface. Grinding experiments showed that the newly developed grinding tools successfully suppressed the clogging and kept the grinding temperature below a critical level for the surgery operation, as compared with the commercial tool.