Lower-Extremity Leg Length Calculation Through 3D Landmark Alignment
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Solution Overview
Problem
Conventional methods for measuring leg length discrepancy (LLD) in orthopedic surgery are unreliable and do not account for the full length of the leg, leading to inaccuracies in pre-operative and intra-operative planning.
Innovation Solution
A computer-implemented method for calculating LLD using patient bone data from medical imaging, identifying anatomical landmarks, and generating three-dimensional models to align femoral and pelvic axes, allowing for precise measurement of leg length discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods are used to measure leg length discrepancy, then the measurement process is simple, but the measurement precision is low and does not account for the full length of the leg
Solution Approach 1:
The leg is segmented into multiple anatomical components (femur, tibia, foot) with specific landmarks identified in each segment. The measurement system divides the leg length calculation into proximal, intermediate, and distal segments, allowing precise measurement of each portion while accounting for the full length from hip to foot.
Solution Approach 2:
The measurement system transitions from conventional one-dimensional linear measurement to three-dimensional spatial measurement using coordinate systems. Anatomical landmarks are positioned in 3D space, and leg length is calculated as the distance between proximal and distal landmarks in three dimensions, providing more accurate measurement that accounts for anatomical curvature and orientation.
2Reliability
If conventional imaging and measurement methods are used, then the process is quick and simple, but the reliability of LLD measurements is low
Solution Approach 1:
Patient bone data is acquired through medical imaging (CT or MRI) before surgery, and three-dimensional computer models are generated in advance. Anatomical landmarks are identified and measured pre-operatively, allowing reliable LLD calculation to be performed before surgical planning, thereby improving reliability without adding time during the surgical procedure.
3Manufacturing precision
If manual measurement methods are used, then the equipment required is minimal, but the accuracy and precision of leg length measurement are insufficient for precise surgical planning
Solution Approach 1:
A three-dimensional computer model copy of the patient's actual bone anatomy is created from medical imaging data. This virtual model allows precise measurement and manipulation without requiring complex physical measurement devices during surgery. The computer model serves as an accurate replica that can be measured and analyzed with high precision using software algorithms.
Data Source
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Figure 2A~2B
Figure 3A
AI summary
A method of calculating leg length discrepancy of a patient body including a first side and a second side, the first side including a first portion of a pelvis, a first femur, a first tibia, and a first foot region, the second side including a second portion of the pelvis, a second femur, a second tibia, and a second foot region, the method comprising: receiving patient bone data associated with the first and a second sides of the patient body, one of the first or second sides including a degenerate or deformed condition, the patient bone data having been generated by a medical imaging device; generating a computer model of the first and second sides of the patient body from the patient bone data; identifying anatomical landmarks in the patient bone data or the computer model, the anatomical landmarks comprising: a first proximal point and a first distal point on the first side; and a second proximal point and a second distal point on the second side; orienting the first and second sides of the computer model relative to each other in a coordinate system such that: a pelvic axis extending through the first and second proximal points are generally perpendicular to a longitudinal axis of the first and second sides of the computer model; and a first axis associated with the first femur and a second axis associated with the second femur are generally parallel to the longitudinal axis; calculating the leg length discrepancy based on the first and second sides of the computer model after orienting the first and second sides of the computer model relative to each other; and displaying at least one of the leg length discrepancy or a portion of the computer model on a display screen.