Force space navigation for robotics

This system is designed to provide spatial movement tracking and robotic end-effector positioning guidance without a secondary tracking system.


Computerized surgical navigation is increasing. Currently, joint replacement and neurosurgery are experiencing rapid growth in the development and clinical use of such systems, which provide improved accuracy and reliable patient outcomes. All of these systems, be they robotic or surgeon navigated, require a spatial tracking system. Most common trackers used surgically are optical trackers, requiring a clear line of sight and potentially impacting surgical workflow, while electromagnetic trackers are more common in biopsy and diagnostic applications.

A tracking system in surgery is required to navigate a pre-operative plan relative to the patient’s anatomy. All current intra-operative tracking systems require tracking devices to be rigidly mounted to the patient’s bones of interest. Stab incisions are made in order to gain access so that tracking targets can be drilled into the bones. These installation sites are most often not part of the surgical incision and exposure itself, which means additional healing and increased risk of infection. This new system does not require any additional stab incisions, instead making use of the already exposed region of bone within the surgical exposure.

Cost also plays a big part in the adoption of surgical systems, whether direct capital costs or time required. The initial capital cost of this system is significantly lower than a typical current tracking system, it requires no passive tracking targets in use so waste and expense are reduced, and there is no optical setup of camera and separate insertion of targets in bone before beginning the surgery, reducing operating room time and resultant cost.

With this significant reduction in adoption costs and avoidance of preparation time in the operating room, we expect this tracking system to encourage the uptake of more robot-assisted systems into more types of procedures, such as upper extremity joint replacement, where there are currently no navigated or robot-assisted systems on the market.

Description of the Invention:

In order to address the limitations of current approaches, researchers at Western University have developed a navigation-by-wire system. This patent-protected innovative technology uses a strain gauge load cell and semi-stiff metal wire to describe movement of a surgical tool relative to patient's anatomy as force data. This force data can be used to monitor relative movement of tool and patient and compensate as necessary. It can also be used to describe the pre-operative plan in terms of force, navigating the surgical tool according to the modeled force data.

The free end of the metal wire attaches to the already exposed bone, avoiding additional stab incisions and extended set-up and calibration. The only part of the system in contact with the patient is the metal wire, greatly simplifying sterilization and reducing the risk of infection.

The accuracy of this navigation system can surpass any existing alternative because the native resolution of the fundamental technology is essentially continuous, limited by the electronic instruments connected to it rather than the load cell itself. In contrast, most current tracking technologies have a fixed resolution. As the most commonly used tracking technology, optical systems have camera chips with a fixed number of pixels and pixel dimensions. Moreover, all current tracking systems navigate by position/orientation, which requires mathematical reduction to position coordinates and orientation angles, or geometric fitting such as least squares algorithms. These methods require complex calibration and induce measurement error. In contrast, this system requires no special calibration and is orders of magnitude more accurate and precise than any current procedure.

Unlike all current tracking systems - electromagnetic, optical or ultrasonic - this system does not suffer interference from electromagnetic, radio, sonic or light sources. In particular, electromagnetic systems can also be impacted by metal surgical tools, the operating table and other metallic objects.

Potential Advantages:

• Compact, accurate and rugged
• Not impacted by multiple sources of interference
• Simple sterilization protocol
• Reduced set-up time, risk of infection and recovery time
• Significant opportunity to reduce cost of equipment

Potential Applications:

• Medical robot guidance in procedures such as biopsy, tumor treatments, neurosurgery and major joint replacement
• Guidance of hand-operated tools
• Industrial equipment guidance

Intellectual Property Protection:

International patent application filed.

Patent Information:

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