Application of instrumented linkage for TKR surgery

Abstract

Coordinate-measuring machines (CMMs) are mechanical systems that use a measuring probe to determine the coordinates of points on the surface of a workpiece. They are used for dimensional measurement, profile measurement, angularity or orientation measurement, depth mapping, digitizing or imaging, and surface definition. An instrumented linkage is a portable CMM with a number of revolute joints, each with encoders to monitor its angular position, thus the orientation as well as the position of the measuring probe can be determined in 3D space. Usually, one end of the linkage is fixed rigidly to a reference table or in some cases to the object being measured. A typical application is the measurement of accuracy of machined parts or surfaces in situ. Since these instruments provide continuous real time feedback and measurement accuracy even down to 0.01 mm they are good candidates for tracking applications. We are currently developing an instrumented linkage that can be used as a navigation tool in total knee replacement (TKR) surgery. This linkage is not unlike a commercial CMM arm such as the Microscsribe (Immersion Corp), with six joints (six degrees-of-freedom) required to fully track the position (x, y, z) and orientation of the end of the arm (roll, pitch, and yaw). Rigid links are joined by revolute joints (. Fig. 78.1) to allow for the manipulation of a digitizing and navigation tool attached to the last link. The design specifications call for a lightweight arm that has the empirically determined range of motion required for the surgical environment, and generates real-time tool position and orientation within 1 mm and half a degree. The tools that are attached to the last link of the arm should be interchanged quickly and the base mount should allow for rigid connection with the bone. © 2007 Springer Medizin Verlag Heidelberg.