Constant-Force Distractor for Dynamic Sizing in Knee Arthroplasty
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Solution Overview
Problem
Current methods for femoral component placement in total knee arthroplasty lack efficient and cost-effective mechanical instrumentation for dynamic sizing and sagittal balancing, particularly in assessing femorotibial joint space at varying degrees of flexion and determining the isometric point of the femur.
Innovation Solution
A device comprising a distractor with a coiled constant force spring and mechanical graph to provide a constant distracting force, allowing for the assessment of femorotibial joint space at all degrees of flexion and identifying the isometric point of the femur, facilitating accurate femoral component placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If robotic technology is used to predict flexion and extension gaps, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex robotic systems with a simplified mechanical distractor device that uses a constant force spring to apply distraction force. This mechanical substitution maintains the ability to measure and predict gaps while eliminating the need for expensive and complex robotic infrastructure, directly addressing the contradiction between measurement precision and device complexity
Solution Approach 2:
The distractor device creates a mechanical copy or simulation of the final implanted state by applying constant distraction force to separate the femur and tibia. This allows surgeons to predict flexion and extension gaps using a simple mechanical model rather than complex robotic prediction systems, achieving accurate gap assessment with reduced device complexity
2Productivity
If mechanical instrumentation is developed for dynamic sizing and sagittal balancing, then productivity is improved, but device complexity increases
Solution Approach 1:
The distractor device is designed as a multi-functional tool that can assess both flexion and extension gaps, evaluate sagittal balance, and determine isometric points throughout the range of motion. This universal design allows a single device to perform multiple surgical assessment functions, improving productivity without requiring multiple separate complex instruments
Solution Approach 2:
The device incorporates dynamic assessment capabilities by allowing measurement at various degrees of flexion and extension. The constant force spring enables the system to adapt to different joint positions dynamically, providing real-time feedback on gap changes throughout the range of motion, thereby improving surgical efficiency with a relatively simple mechanical design
3Measurement precision
If constant distracting force is applied to assess joint space at all degrees of flexion, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The constant force spring is designed to automatically maintain constant distraction force throughout the range of motion without requiring active control or adjustment by the surgeon. The spring's inherent mechanical properties provide the constant force self-regulating mechanism, achieving precise joint space measurement capability with minimal added device complexity
Solution Approach 2:
The patent utilizes the physical properties of constant force springs, which maintain constant force over a range of displacement. This parameter characteristic of the spring allows the device to maintain consistent measurement conditions across all degrees of flexion, improving measurement precision while keeping the spring mechanism itself relatively simple
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 reliable restoration of native joint balance and creation of a dynamic flexion gap, ensuring sagittal balance through all degrees of flexion, with improved accuracy and cost-effectiveness compared to existing technologies.
Implementation Method 1
a coiled constant force spring disposed in the spring housing, the spring housing attached to an outer end of the coiled constant force spring, the coiled constant force spring configured to apply the constant distracting force on the at least one femoral paddle
Data Source
AI summary
The present disclosure describes one or more embodiment of devices for assisting femoral component placement in total knee arthroplasty. The device may include a distractor configured to provide a constant distracting force. The distractor may include a main body of the distractor, a tibial paddle fixedly connected to the main body, the tibial paddle configured to engage a top of a tibia, at least one femoral paddle configured to push against a bottom of a femur, a spring housing fixed on the main body of the distractor, and a coiled constant force spring disposed in the spring housing. The spring housing is attached to an outer end of the coiled constant force spring, and the coiled constant force spring is configured to apply the constant distracting force on the at least one femoral paddle. The device further includes a mechanical apparatus for locating an isometric point of the femur.