Inertial Sensor Cup Positioning Instrument
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Solution Overview
Problem
Conventional surgical techniques for hip implant positioning, such as 'eyeballing' and mechanical tools, are inadequate for achieving accurate alignment, leading to sub-optimal implant placement, increased wear, and potential failure, while existing computer-assisted surgery systems face issues like high costs and electromagnetic interference.
Innovation Solution
A method and system utilizing inertial sensors to assist in positioning the acetabular cup, involving a cup positioning instrument with a visual guide and inertial sensor unit, which is calibrated based on pre-operative planning and anatomical landmarks to achieve precise abduction and anteversion angles, allowing for accurate cup orientation and impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mechanical tools or eyeballing methods are used for positioning, then device complexity is reduced, but manufacturing precision and measurement precision deteriorate
Solution Approach 1:
The patent replaces complex optical-mechanical tracking systems with an inertial sensor-based system. The inertial measurement unit (IMU) directly measures acceleration and orientation without requiring external optical infrastructure, thereby reducing device complexity while maintaining or improving positioning accuracy through sophisticated sensor fusion algorithms.
Solution Approach 2:
The system creates a virtual model of the patient's anatomy based on pre-operative imaging (CT or MRI scans) and uses this digital copy to guide the surgical procedure. The inertial sensors track the actual instrument positions and compare them against the virtual anatomical model, enabling precise cup positioning without requiring complex physical tracking infrastructure.
2Measurement precision
If optical or magnetic tracking systems are used, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent substitutes optical-mechanical tracking systems with an inertial sensor system. Instead of using cameras and reflective markers or magnetic fields, the system employs accelerometers, gyroscopes, and magnetometers integrated in an IMU to directly measure orientation and position, significantly reducing device complexity while maintaining measurement precision through sensor fusion algorithms.
3Measurement precision
If optical or magnetic tracking systems are used, then measurement precision improves, but reliability deteriorates due to electromagnetic interference
Solution Approach 1:
The patent acknowledges that magnetic fields can interfere with magnetic tracking systems, but turns this to advantage by using the magnetometer in the inertial sensor system to measure and compensate for magnetic field distortions in the operating room environment. The system characterizes the magnetic field environment and uses this information to correct measurements, converting the harmful interference into useful calibration data that improves both accuracy and reliability.
4Reliability
If inertial sensors are used, then device complexity is reduced and reliability improves, but measurement precision may deteriorate
Solution Approach 1:
The patent combines multiple types of sensors (accelerometers, gyroscopes, and magnetometers) into a single inertial measurement unit. Each sensor type measures different aspects of motion and orientation, and their data are fused through sophisticated algorithms to produce accurate and reliable orientation measurements. This multi-sensor approach compensates for the individual weaknesses of each sensor type while maintaining system simplicity.
Solution Approach 2:
The system continuously monitors sensor outputs and uses feedback control to correct for drift and accumulation of errors. The inertial sensors provide continuous orientation data that is compared against the pre-operative virtual model and real-time visual feedback is provided to the surgeon, enabling precise positioning while maintaining system reliability through ongoing error correction.
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 approach provides a cost-effective and interference-resistant method for accurately positioning the acetabular cup, reducing the risk of implant failure and improving long-term operability by aligning the cup with precise abduction and anteversion angles.
Implementation Method 1
The cup positioning instrument includes an inertial sensor unit with pre-planned orientation data for a desired cup orientation based on at least one landmark of the pelvis
Data Source
AI summary
A method for assisting in positioning the acetabular cup comprises orienting a cup positioning instrument with a cup thereon in an initial reference orientation relative to an acetabulum of a pelvis with the cup forming a joint with the acetabulum, the cup positioning instrument comprising an inertial sensor unit with pre-planned orientation data for a desired cup orientation based on at least one landmark of the pelvis, The cup positioning instrument is rotated to a desired abduction angle as guided by an interface of the cup positioning instrument, based on movements relative to at least one landmark. The cup positioning instrument is rotated to a desired anteversion angle as guided by the interface of the cup positioning instrument, based on movements relative to the at least one landmark. Upon reaching the desired cup orientation as indicated by the interface, the cup is impacted into the acetabulum.