Inertial Sensor Distance Calculation for Bone Navigation
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Solution Overview
Problem
Existing computer-assisted surgery technologies face challenges with operative time, line-of-sight constraints, and cost-effectiveness, particularly in providing accurate positional data using inertial sensors.
Innovation Solution
A method and system utilizing inertial sensors, including accelerometers and gyroscopes, to calculate the distance between fixed points on a bone by obtaining acceleration data and angular rates of change, and processing this data to determine the distance vector between the sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical navigation is used for computer-assisted surgery, then navigation accuracy is improved, but operative time increases and line-of-sight constraints hamper surgical flow
Solution Approach 1:
The patent replaces optical navigation systems with inertial sensors (accelerometers and gyroscopes) that use mechanical sensing of motion and gravity. This substitution eliminates the need for complex optical tracking infrastructure while providing continuous position and orientation data without line-of-sight constraints, thereby reducing operative time while maintaining navigation accuracy.
Solution Approach 2:
The patent extracts the essential navigation function from the complex optical system by using only inertial sensors attached directly to surgical instruments. This extraction removes the need for external optical cameras, reference frames, and line-of-sight requirements, simplifying the system and reducing setup time while preserving the core capability of tracking instrument position and orientation.
2Measurement precision
If C-arm validation equipment is used for bone measurement, then post-operative validation is achieved, but the equipment is bulky and not cost-effective for intra-operative use
Solution Approach 1:
The patent replaces bulky C-arm imaging equipment with compact inertial sensors that directly measure bone position and orientation through acceleration and angular rate detection. This mechanical sensing approach provides intra-operative feedback without requiring large imaging equipment, reducing both device complexity and cost while enabling real-time measurement during surgery.
Solution Approach 2:
The patent employs inexpensive, disposable inertial sensor units that can be attached to surgical instruments or bone surfaces. These low-cost sensors provide accurate measurement data for the duration of the procedure and are then discarded, eliminating the need for expensive, reusable C-arm equipment while maintaining measurement precision.
3Ease of manufacture
If inertial sensors are used for positional data, then cost-effectiveness and immunity to environmental factors are improved, but accurate positional data calculation is difficult since sensors primarily provide orientation data
Solution Approach 1:
The patent transitions from using inertial sensors solely for orientation measurement to calculating three-dimensional positional data by integrating acceleration data across multiple sensors arranged in specific geometries. By adding the dimension of spatial configuration among multiple sensors, the system derives position information from primarily orientation-providing sensors, overcoming the limitation while maintaining cost-effectiveness.
Solution Approach 2:
The patent introduces mathematical integration algorithms and sensor fusion techniques as intermediaries that transform raw acceleration and orientation data into accurate positional information. These computational mediaries bridge the gap between what inertial sensors naturally measure (orientation and acceleration) and the desired output (precise position), enabling accurate positional data calculation without changing the physical sensors themselves.
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 allows for accurate and cost-effective calculation of distances on a bone, immune to environmental factors like magnetic fields, and capable of operating under a wide range of conditions, enhancing surgical precision and efficiency.
Implementation Method 1
obtaining, using one or more processors within a computing system, first acceleration data from a first accelerometer unit located at a first fixed location relative to the bone
Implementation Method 2
simultaneously obtaining, using the one or more processors within the computing system, angular rates of change from at least one gyroscope unit fixed to the bone
Data Source
AI summary
A computer-assisted surgery system for obtaining a distance between at least two fixed points relative to a bone comprises a first accelerometer unit located at a first fixed location on the bone, and producing first acceleration data during a movement of the bone. A second accelerometer unit is located at a second fixed location on the bone, and simultaneously producing second acceleration data during the movement. A gyroscope unit is fixed to the bone and simultaneously producing angular rates of change of said movement. A processor unit obtains the acceleration data and the angular rates of change for calculating the distance between the first fixed position and the second fixed position on the bone using a distance value of a distance vector between the accelerometer units. An interface outputs the distance between the first fixed position and the second fixed position relative to the bone. A method for calculating a distance between at least two points on a bone is provided.