Freehand Navigation For Bone Shaping

This chapter describes a method for carrying out knee-replacement surgery where the bone cuts are made freehand, guided by feedback from a computer screen or other means, as opposed to the standard surgical techniques using jigs and fixtures. The potential advantages of freehand navigation are speed, simplicity and accuracy, together with no increase in the cost per procedure. There are numerous total and unicondylar knee systems, each with its own technique, frequently more than one for a particular design. However, there are many similarities between the techniques, the common element being a set of jigs and fixtures which are sequentially positioned on the bones in order to guide the cuts. The goal is to achieve an accurate fit of the components on to the bones, and an accurate overall limb alignment. While experience has shown that the components seldom fit exactly on to the bones, the size of the gaps and irregularities have not been quantified to our knowledge. When cement is used, small gaps may not be important, but that is not the case for uncemented components.