An unconstrained virtual bone clamper for a knee surgical robot using visual servoing technique

Medical robotics has high potential to bring patients real benefits due to its high accuracy positioning capability. However a patient's organ movement is still a challenge for medical robotics in achieving the expected high positioning accuracy. In orthorpaedic surgery, the target object is hard tissue. Obtaining accurate positioning is usually easier than with a soft tissue target. In the past, the solution was to use a mechanical clamper to fix and prevent the bone from moving. However, the invasive bone clamping approach has several drawbacks, such as additional damage to the bone, large errors for a loose bone, and constraints of ligament adjustment etc. Therefore, in this paper, an unconstrained virtual bone clamper has been proposed. Its aim is to provide the same bone freezing function as a traditional bone clamp, but it is implemented by software. The drawbacks of a physical bone clamp can be avoided. Experimental results on plastic sawbones resection demonstrate that using the virtual clamp, a robot can achieve accuracy as good ad when using a physical clamp whether the bone is fixed in place or moving.