Femur Axis Determination Device with Lockable Shaft and Force-Torque Sensor
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Solution Overview
Problem
Current methods for aligning knee prostheses with the mechanical leg axis, such as using intramedullary pins or navigation systems, are invasive, risky, or require significant effort, and there is a need for a simpler and more accurate method to determine the mechanical leg axis of the femur for proper prosthesis alignment.
Innovation Solution
A device with a lockable, angle-variable fastening mechanism connected to the femur's knee joint and a force-torque measuring system that splits applied forces into measurable components, allowing for precise alignment along the mechanical leg axis by minimizing transverse forces and moments, which can be displayed electronically or mechanically for operator adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intramedullary pin is inserted into femoral medullary canal to approximate correct alignment, then alignment accuracy is improved, but invasiveness and embolism risk increase
Solution Approach 1:
The invention extracts the alignment determination function from the invasive intramedullary pin method and implements it through an external device that attaches to the knee joint, eliminating the need to penetrate the femoral medullary canal while maintaining alignment measurement capability
Solution Approach 2:
The device uses an external shaft and force application mechanism as an intermediary to determine the mechanical leg axis without directly inserting instruments into the bone marrow, thereby avoiding bone marrow compression and embolism risk while still achieving accurate alignment determination
2Measurement precision
If navigation systems are used to guide knee operations, then alignment accuracy is improved, but operational complexity and time consumption increase
Solution Approach 1:
The device enables the surgeon to directly determine the mechanical leg axis through simple force application and measurement without requiring external navigation systems, planning software, or tracking systems, making the alignment process self-contained and straightforward
Solution Approach 2:
The invention extracts the alignment determination capability from complex navigation systems and implements it through a dedicated device that provides direct mechanical axis measurement without requiring software planning or tracking infrastructure
3Measurement precision
If force-torque measuring device is used to measure transverse forces and moments, then alignment precision is improved, but device complexity increases
Solution Approach 1:
The force-torque measuring device serves multiple functions: it measures both longitudinal and transverse force components, determines the mechanical leg axis, and guides prosthesis alignment, thereby justifying its complexity through multifunctional utility
Solution Approach 2:
The invention replaces complex navigation systems and software-based alignment methods with a mechanical force-torque measuring device that directly measures physical quantities (forces and moments) to determine alignment, substituting computational complexity with mechanical measurement
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 accurate determination of the mechanical leg axis, reducing the risk of invasive procedures and improving the longevity of artificial knee joints by ensuring proper alignment, and can be used as a preparation for knee operations with minimal invasiveness.
Implementation Method 1
each web having at least one force sensor, in particular a strain gauge
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
The invention relates to a device for determining the mechanical leg axis of a femur. Said device is provided with a shaft (3) that comprises, on one of its ends, a securing device (5) that is connected to the shaft and that can be blocked at various angles, in order to obtain a fastening that can be blocked in an angle stable manner and that fastens the shaft (3) to the knee joint of a femur, and comprises a gripping element (10) on its other end. A force-torque measuring device (14) is arranged between the gripping element (10) and the shaft (3), said device enabling the longitudinal and/or transversal force components of force (Fz) exerted via the shaft (3) upon the knee joint to be measured by means of the gripping element (10) and/or torque produced thereby. The invention also relates to a method for determining the mechanical leg axis of a femur by means of the above mentioned device. The shaft (3) is fixed in its position by blocking at various angles, in particular an articulated connection when the measured transversal force components or torque produced thereby is minimised, in particular, is zero.