Joint Range of Motion Estimation Using Polar Coordinate Mesh Analysis
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Solution Overview
Problem
During joint surgeries, such as total hip replacements, accurately determining the range of motion (ROM) of a joint is challenging due to the sensitivity of implant positioning, which affects the ROM and the points of contact between bones, making optimal implant placement difficult.
Innovation Solution
A computer-implemented method using digital models of bones represented by mesh points to calculate angular distance values in polar coordinates, allowing for efficient estimation of joint ROM without the need for gradual rotation, and enabling visualization of limiting areas for surgical intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional methods are used to determine joint range of motion, then the measurement may be more comprehensive, but the computational complexity and time required increase significantly
Solution Approach 1:
The patent replaces traditional mechanical measurement methods (physical manipulation and gradual rotation of digital models) with a computational approach using polar coordinate transformation. This substitution enables rapid calculation of angular distances between mesh points through mathematical formulas rather than iterative mechanical simulation, achieving both high computational efficiency and measurement accuracy.
Solution Approach 2:
The patent transforms the coordinate system from Cartesian to polar coordinates, changing the mathematical parameters used to represent bone positions. This parameter transformation allows direct calculation of angular distances using polar coordinate formulas (r, θ), where the angular component θ directly provides the rotation angle, eliminating the need for gradual mechanical rotation and significantly improving computational speed while maintaining precision.
2Reliability
If implant positioning is adjusted to optimize range of motion, then the surgical outcome may improve, but the complexity of planning and decision-making increases
Solution Approach 1:
The patent creates a digital copy (virtual model) of the patient's joint anatomy using mesh representations of bones. This digital twin allows surgeons to perform virtual implant positioning and range of motion calculations without affecting the actual patient, enabling multiple scenario testing and optimization before surgery. The virtual model accurately replicates anatomical structures, allowing reliable prediction of surgical outcomes.
Solution Approach 2:
The patent enables preliminary calculation of range of motion for different implant positions before actual surgery. By computing angular distances and identifying contact points in advance using the polar coordinate method, surgeons can pre-determine optimal implant positioning strategies, reducing intraoperative decision-making complexity and improving surgical planning efficiency.
3Measurement precision
If the digital model includes detailed mesh points for accurate calculation, then the measurement precision improves, but the computational resources and time required increase
Solution Approach 1:
The patent transforms detailed spatial coordinate data into polar coordinates (r, θ), where the angular parameter θ directly represents the rotation angle. This parameter transformation allows direct extraction of angular distance information from the polar coordinate representation, enabling accurate range of motion calculation even with detailed mesh models, while the mathematical efficiency of polar coordinate arithmetic reduces computation time compared to Cartesian coordinate methods.
Solution Approach 2:
The patent replaces iterative mechanical rotation simulation with direct mathematical calculation using polar coordinate transformation. Instead of gradually rotating the digital model and checking for contact at each step, the system uses the polar coordinate formula to directly compute the angular distance between mesh points, achieving the same measurement precision with significantly reduced computational time.
Data Source
AI summary
A system and method (100) for estimating range of motion of a joint (3) connecting a first bone (5) to a second bone (7), the joint comprising a point of rotation (9) defining rotation of the first bone relative to the second bone. The method comprises: obtaining (110) a digital model of the joint that includes, for each bone (5, 7), respective mesh models with sets of mesh points that represent the bone; determining (120) polar coordinates for the set of mesh points, with the point of rotation (9) as a pole (21) of the polar coordinates; and calculating (130), based on the polar coordinates, multiple angular distance values relating to rotation of the joint, where the multiple angular distance values are indicative of an angular distance between points in the set of mesh points, and the angular distance being indicative of the range of motion of the joint.