Cutting Assembly Sensor Mounting for Electromagnetic Tracking
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Solution Overview
Problem
Electromagnetic tracking systems face errors in positioning due to magnetic interference from spinning surgical tools like shavers during FAI surgery, where the geometry of the hip area obstructs optical tracking and deformation or flexion of instruments introduces additional errors.
Innovation Solution
A cutting assembly with a bur assembly and sheath assembly that includes a sensor to measure the electrical field, minimizing magnetic interference by positioning the sensor to transmit accurate readings to a computing device, which determines the cutting assembly's position within the electromagnetic field, while the suction aperture removes debris and the shaft provides a fluid connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor is positioned close to the cutting assembly to minimize error from material deformation and distance, then measurement precision is improved, but magnetic interference from spinning metal increases causing positioning errors
Solution Approach 1:
A non-magnetic shaft material acts as an intermediary between the motor and the bur assembly, allowing mechanical power transmission while minimizing magnetic interference with the electromagnetic tracking sensor. The shaft is specifically designed with non-magnetic properties to mediate between the motor's magnetic field and the sensor's electromagnetic field.
Solution Approach 2:
The patent changes the magnetic properties parameter of the shaft material from magnetic to non-magnetic, fundamentally altering how the system handles electromagnetic interference. This parameter change allows the sensor to operate accurately while the bur assembly spins, as the non-magnetic shaft does not distort the electromagnetic field.
2Measurement precision
If optical tracking is used for FAI surgery, then tracking can be performed, but the geometry of the hip area obstructs the camera view causing tracking errors
Solution Approach 1:
The patent replaces the optical tracking system with an electromagnetic tracking system. Instead of using cameras that require line of sight, the system uses electromagnetic fields that can penetrate tissue and operate without direct visual contact between the sensor and the surgical site, eliminating the line of sight constraint.
3Strength
If the shaft connecting the bur to the motor is made magnetic for structural strength, then strength is improved, but it introduces error into the electromagnetic field readings
Solution Approach 1:
The patent employs composite material construction for the shaft, combining non-magnetic materials with structurally strong materials to achieve both mechanical strength and electromagnetic compatibility. This allows the shaft to maintain necessary strength while not interfering with the electromagnetic tracking field.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration minimizes errors caused by spinning metal and deformation, providing more accurate electromagnetic field readings and reducing interference, thus enhancing the precision of the electromagnetic tracking system during surgical procedures.
Implementation Method 1
a sensor configured to measure an electrical field around the cutting assembly
Data Source
AI summary
A cutting assembly (200) is configured for use with an electromagnetic tracking system (1). The cutting assembly comprises a bur assembly (10) and a sheath assembly (100). The sheath assembly comprises a sensor (135) configured to measure an electrical field around the cutting assembly, a wire (130) configured to operably connect the sensor and an external computing device (6), and a sensor mount (110) affixed to at least a portion of the sheath assembly, the sensor mount configured to house the sensor and at least a portion of the wire. The sheath assembly is configured to receive at least a portion of the bur assembly such that any impact from magnetic interference caused by, for example, a cutting device (40) within the bur assembly on the sensor is minimized when the cutting device is cutting a patient's bone.