Prosthetic Trial Base Rotation Restrictor
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Solution Overview
Problem
Current joint replacement surgery tools, such as externally-fixated jigs and trials, are cumbersome, time-consuming, and unreliable for assessing joint kinematics due to their bulkiness and the risk of leaving debris in the bone, and they do not effectively inhibit rotation of prosthetic stems within the medullary canal.
Innovation Solution
A trial base with a stem and fins that are hingedly or flexibly connected, featuring a mechanism to drive the fins apart, which are designed to engage the bone and inhibit rotation, using a collar and bolt system or a cam and rod mechanism to secure the stem in place, thereby ensuring accurate joint kinematics assessment without leaving debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If externally-fixated jigs are used to assess joint kinematics, then the assessment can be performed, but the devices are bulky, complex, time-consuming to set up, and require external fixation devices and power tools
Solution Approach 1:
The trial base is divided into a stem portion and a collar portion that can be separately inserted and assembled. The stem is inserted into the medullary canal first, then the collar is assembled onto the stem and secured with set screws, eliminating the need for complex external fixation devices and power tools while maintaining assessment reliability
Solution Approach 2:
The invention extracts the essential function of joint kinematics assessment from the complex external jig system and relocates it to a simplified internal trial base device that fits within the medullary canal, removing the need for external fixation components
2Measurement precision
If externally-fixated jigs are used to assess joint kinematics, then the assessment can be performed, but they are cumbersome making accurate range of motion assessment difficult
Solution Approach 1:
The trial base is designed to be nested within the medullary canal, with the stem inserted inside the canal and the collar assembled onto the stem. This nested configuration provides a compact, maneuverable device that is easy to operate and allows for precise range of motion assessment without the bulkiness of external jigs
3Reliability
If a lap sponge is used to hold the trial within the medullary canal, then the trial can be secured, but the stem may be allowed to move within the joint leading to unreliable joint kinematics assessment
Solution Approach 1:
The trial base is segmented into a stem and collar that work together to provide fixation. The collar wraps around the stem and is secured with set screws that engage with the bone, creating a two-part system that prevents stem movement while maintaining assessment reliability
Solution Approach 2:
The stem and collar are combined into a single trial base assembly where the collar is secured to the stem through set screws. This merged structure provides both secure fixation and reliable joint kinematics assessment by eliminating stem movement
4Ease of manufacture
If a lap sponge is used to hold the trial within the medullary canal, then the trial can be secured, but there is a risk of leaving sponge or cloth debris behind in the bone after the trial is removed
Solution Approach 1:
The invention extracts the fixation function from the lap sponge material and transfers it to a metal collar and set screw system. This eliminates the harmful effect of leaving sponge or cloth debris in the bone while maintaining ease of assembly through the modular stem-and-collar design
Solution Approach 2:
The trial base is designed as a disposable device that is inserted, used for assessment, and then removed as a single unit. The metal construction allows for easy removal without leaving debris, replacing the need for reusable lap sponges that can leave harmful material behind
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 solution provides a more accurate and reliable assessment of joint kinematics by securely fixing the trial base within the medullary canal, reducing the risk of debris and improving the precision of prosthetic placement, thus enhancing the surgical procedure's efficiency and effectiveness.
Implementation Method 1
a bolt drivable relative to the collar and into a space between the tabs to act as a wedge and force the tabs apart
Implementation Method 2
a cam and a rod extending between the fins, with the cam either being fixed to the rod between the fins so that rotating the rod causes the cam to force the fins apart or being positioned at a proximal end of the rod so that rotating the cam can force the rod to move axially to act as a wedge and force the fins apart
Implementation Method 3
rotating the cam can force the rod to move axially to act as a wedge and force the fins apart
Implementation Method 4
The fins may be hingedly or flexibly connected to one another
Data Source
AI summary
A prosthetic trial base includes a hinge and two levers connected to one another by the hinge. Each lever includes a tab extending proximally of the hinge and a fin extending distally of the hinge. The prosthetic trial base also includes a head movable between the tabs to force the tabs apart from one another. The trial base also includes a collar defining a bore in which the tabs are received and a lid that is connected to the levers. The head and is connected to the lid in a manner that enables the head to be driven relative to the lid.