Variable Angle Humeral Component Locking System
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Solution Overview
Problem
Current variable angle humeral components for shoulder arthroplasty do not adequately accommodate angular variability, leading to potential clearance or impingement issues between the humeral head and resected metaphyseal bone, and fail to satisfactorily integrate both standard and eccentric components.
Innovation Solution
A variable angle locking system comprising a humeral component with a cavity, a humeral stem, a washer with a threaded portion, an adaptor with an arcuate inner wall and fixation peg, a spring washer, and a screw with helical threads, allowing for angular adjustment and secure locking at multiple angles relative to a common axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed angle humeral component system is used, then the structure is simple and easy to manufacture, but it cannot accommodate angular variability in humeral cuts, leading to clearance or impingement issues
Solution Approach 1:
The locking system transitions from a fixed angle configuration to a dynamic variable angle configuration. The humeral component can be locked at multiple angles (e.g., 0°, 15°, 30°) relative to the humeral stem through a movable locking mechanism that allows angular adjustment before final securing, enabling adaptation to different humeral cut angles while maintaining structural integrity.
Solution Approach 2:
The locking system is divided into separable components including the humeral stem, humeral component, and locking mechanism. This segmentation allows independent optimization of each component and enables the humeral component to be positioned at different angles relative to the stem before locking, resolving the contradiction between adaptability and complexity.
2Adaptability or versatility
If a variable angle locking system is implemented, then angular variability is accommodated, but the device complexity increases with multiple components and locking mechanisms
Solution Approach 1:
The locking mechanism is integrated into the humeral component-stem assembly, combining the functions of positioning and locking into a unified system. The angular adjustment capability and locking function are merged rather than being separate systems, reducing overall complexity while maintaining variable angle capability.
Solution Approach 2:
The locking system is designed to accommodate both standard and eccentric humeral components through a universal interface. The same locking mechanism can secure different types of humeral components at multiple angles, eliminating the need for separate locking systems for different component types and reducing overall device complexity.
3Adaptability or versatility
If angular adjustment is allowed, then patient anatomy and surgical requirements are accommodated, but ensuring secure locking at multiple angles becomes more difficult
Solution Approach 1:
The locking mechanism utilizes changes in mechanical parameters (such as friction coefficients, contact forces, or geometric constraints) to maintain secure locking across different angular positions. The system is designed so that the locking force and stability are maintained consistently regardless of the selected angle, ensuring reliability throughout the full range of motion.
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
The system provides angular variability of up to +/- 15 degrees in version and inclination, enhancing joint stability and preventing dislocation by allowing for secure angular adjustment of the humeral head relative to the humeral stem, accommodating individual patient anatomy and varying surgical requirements.
Implementation Method 1
a spring washer positioned between the first washer and the elongated fixation peg
Implementation Method 2
a screw including a head portion having helical threads and an elongated shaft portion extending from the head portion
Implementation Method 3
the screw being configured to lock the humeral component to the humeral stem at more than one angle relative to a common axis
Data Source
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AI summary
A variable angle locking system comprising a humeral component having an underside at least partially defined by a cavity; a humeral stem couplable to the humeral component; a first washer defining a first through-hole and including a threaded portion; an adaptor defining a second through-hole and having a shelf portion and an elongated second washer, the shelf portion being adapted to be received by the cavity of the humeral component; a spring washer positioned between the first washer and the elongated second washer and defining a third through-hole; and a screw configured to lock the humeral component to the humeral stem at more than one angle relative to a common axis defined by the first, second and third through-holes, the screw including a head portion having helical threads and an elongated shaft portion extending from the head portion.