Inertial Sensor Registration for Surgical Navigation
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Solution Overview
Problem
Current computer-assisted surgery methods for orienting implants, such as acetabular cup implants, face challenges with inaccurate positioning due to the lack of precise three-dimensional orientation, leading to issues like loss of movement and premature wear, and existing tracking technologies like optical navigation and C-arm validation are either cumbersome, costly, or lack quantitative assessment.
Innovation Solution
An apparatus and method utilizing inertial sensors to determine the orientation of a distance-measurement device relative to an anatomical feature, allowing for accurate modeling and navigation of the implant placement by securing a base to the bone, using a spherical joint and distance-measurement device, and processing units to generate a coordinate system model and output orientation data for precise tool positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical navigation is used for tracking, then measurement precision is improved, but device complexity and operative time increase due to line-of-sight constraints
Solution Approach 1:
The patent replaces optical navigation systems with inertial sensors (accelerometers, gyroscopes, magnetometers) that use mechanical/physical sensing of motion and orientation. This substitution eliminates the need for complex optical tracking infrastructure while maintaining measurement precision for determining the position and orientation of surgical tools relative to the bone.
2Measurement precision
If C-arm validation is used for assessment, then measurement precision is improved, but device complexity and cost increase with bulky equipment
Solution Approach 1:
The patent replaces bulky C-arm imaging equipment with compact inertial sensors integrated into the surgical tool handles. These sensors provide real-time positioning and orientation data without requiring large external imaging equipment, thereby reducing device complexity while maintaining assessment accuracy.
3Ease of operation
If manual reference guides are used for orientation, then ease of operation is improved, but measurement precision deteriorates due to lack of patient position accounting
Solution Approach 1:
The patent enables the surgical tool to self-measure its own position and orientation through integrated inertial sensors. The system automatically accounts for patient positioning and tool orientation by having the sensors directly measure these parameters, eliminating the need for external manual reference guides while maintaining both ease of operation and measurement precision.
4Ease of manufacture
If inertial sensors are used for tracking, then cost is reduced and information value is improved, but measurement precision may deteriorate without proper reference establishment
Solution Approach 1:
The patent performs preliminary registration of the inertial sensor to the bone surface before the surgical procedure begins. This preliminary action establishes an accurate reference coordinate system that allows the inertial sensors to provide precise orientation measurements throughout the surgery, thereby maintaining measurement precision while achieving cost-effectiveness.
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
Enables cost-effective and precise orientation of implants during surgery, reducing the risk of improper placement and subsequent complications, while providing real-time tracking and quantitative assessment of implant positioning.
Implementation Method 1
a spherical joint supported by the base, the spherical joint having a ball member rotatable in at least two rotational degrees of freedom relative to the base and having a center of rotation fixed relative to the base
Implementation Method 2
at least one receptacle configured to receive an inertial sensor unit for determining an orientation of the distance-measurement device
Implementation Method 3
a distance-measurement device connected to the ball member such that a distance-measurement axis of the distance-measurement device passes through said center of rotation of the ball member, the distance-measurement device configured for providing a distance of any point of the surface intersecting the distance-measurement axis
Data Source
AI summary
A computer-assisted surgery (CAS) system for navigating a surface of an anatomical feature in a coordinate system comprises an apparatus for obtaining points of a surface of an anatomical feature including a base adapted to be secured to the anatomical feature, a spherical joint supported by the base, the spherical joint having a ball member rotatable in at least two rotational degrees of freedom relative to the base and having a center of rotation fixed relative to the base, a distance-measurement device connected to the ball member such that a distance-measurement axis of the distance-measurement device passes through said center of rotation of the ball member. An inertial sensor unit produces signals representative of the orientation of the distance-measurement device. A CAS processor receives the signal from the at least one inertial sensor unit and outputs orientation data relating at least an object relative to the surface of the anatomical feature using the model of the surface in the coordinate system and the signals from the at least one inertial sensor unit.