Expandable Trial Stem for Orthopaedic Surgery
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Solution Overview
Problem
Current devices for assessing joint kinematics during joint arthroplasty procedures are either cumbersome and complex or unreliable due to the use of external fixation devices and temporary materials like sponges, which can lead to inaccurate assessments and debris in the bone.
Innovation Solution
A trial device with a distal portion featuring an expandable bone-engaging surface and a driver mechanism that allows for precise positioning and securement within the bone canal, providing accurate joint kinematics evaluation without external fixation and minimizing debris.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If externally-fixated jigs are used for joint kinematic evaluation, then the assessment can be performed, but the device becomes bulky, complex and time consuming to set up and use
Solution Approach 1:
The invention removes the external fixation components and power tools from the system, extracting only the essential trial device that can be inserted directly into the medullary canal. This eliminates the bulky external jigs while maintaining the ability to assess joint kinematics through the simplified internal trial device.
Solution Approach 2:
The trial device serves as an intermediary component that temporarily replaces the need for complex external fixation systems. By positioning the trial within the medullary canal and using a lap sponge as a mediator for pressure fit, the system achieves reliable kinematic assessment without requiring external jigs.
2Reliability
If externally-fixated jigs are used for joint kinematic evaluation, then the assessment can be performed, but external fixation devices and power tools are required which introduce further complications
Solution Approach 1:
The invention extracts and eliminates the need for external fixation devices and power tools from the surgical procedure. The trial device can be inserted and secured using only manual techniques and basic surgical instruments, significantly simplifying the ease of operation while maintaining assessment reliability.
3Ease of operation
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 invention changes the physical state and positioning parameters of the lap sponge to optimize its function. By carefully controlling the placement and compression of the sponge, the trial achieves sufficient stability to prevent movement while maintaining reliable joint kinematics assessment. The parameter control involves precise positioning and controlled compression forces.
4Ease of operation
If a lap sponge is used to hold the trial within the medullary canal, then the trial can be secured, but sponge or cloth debris may be left behind in the bone after the trial is removed
Solution Approach 1:
The invention addresses the potential harm of debris by converting the temporary use of lap sponge into a controlled process. The sponge is used only temporarily during positioning, then completely removed along with the trial device. The principle transforms the potential harmful residue into a beneficial temporary aid that is fully extractable, leaving no debris in the bone.
5Reliability
If features are included on the outside surface of the stem for permanent implantation, then bony ingrowth and adhesion are promoted, but these features are not well-suited for use during joint kinematic assessment
Solution Approach 1:
The invention segments the implant system into two distinct components: a trial device for kinematic assessment and a permanent implant for fixation. The trial device has a smooth surface optimized for assessment, while the permanent implant includes features for bony ingrowth and adhesion. This segmentation allows each component to be optimized for its specific function without compromise.
Solution Approach 2:
The invention applies dynamics by making the trial device removable and replaceable. The trial portion can be inserted and removed multiple times during assessment, while the permanent implant with fixation features is installed only after optimal positioning is determined. This dynamic approach allows the system to adapt between assessment and permanent fixation modes.
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 device enables reliable and accurate assessment of joint kinematics, ensuring proper positioning of prosthetic implants and reducing the risk of debris in the bone, thereby improving the precision and safety of joint replacement surgeries.
Implementation Method 1
movement of the driver, preferably in a distal direction, causes movement of a portion of the first arm away from a portion of the second arm
Data Source
AI summary
A trial device and a method for using the device in surgery are disclosed. The device includes a body including a proximal portion and a distal portion. The proximal portion has a post or trunion projecting therefrom. The distal portion extends from the proximal portion and includes a first arm and a second arm, the first and second arms being movable with respect to one another. The body further includes a cavity formed therein so as to extend through the proximal portion and into the distal portion. The device further includes a driver adapted for sliding engagement within the internal cavity of the body such that movement of the driver, preferably in a distal direction, causes movement of a portion of the first arm away from a portion of the second arm.