Impactor-Extractor Tool for Prosthetic Stem Placement
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Solution Overview
Problem
Incorrect installation of prosthetic stems can lead to pain, limited range of motion, increased wear debris, and reduced joint stability, resulting in a shorter lifespan of the prosthesis.
Innovation Solution
The development of an impactor-extractor tool with a body, lever, lock, and linkages that allows for secure engagement and disengagement of the stem, enabling precise placement and removal of prosthetic stems within bones, utilizing taper connectors and a sleeve system to accommodate varying stem sizes and surgical procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a prosthesis stem is installed using conventional methods, then the installation can be completed, but the placement precision is insufficient leading to incorrect positioning
Solution Approach 1:
The impactor-extractor tool serves as an intermediary device between the surgeon and the prosthesis stem. It includes a connector that interfaces with the stem's drive slot, providing controlled force transmission during installation and extraction. This intermediary mechanism ensures precise placement by allowing controlled tapping forces to be transmitted along the stem's longitudinal axis, preventing lateral forces that could cause misalignment.
Solution Approach 2:
The invention replaces conventional manual installation methods with a specialized mechanical tool system. The impactor-extractor incorporates a lever arm mechanism that provides mechanical advantage, allowing the surgeon to apply controlled forces to the stem during installation. The tool's geometry and linkage mechanisms substitute for less precise manual manipulation, ensuring accurate stem positioning within the bone canal.
2Ease of repair
If the stem needs to be extracted for revision or adjustment, then removal is necessary, but conventional extraction methods may damage the implant or surrounding anatomy
Solution Approach 1:
The impactor-extractor tool serves as a protective intermediary during extraction. The connector engages with the stem's drive slot, distributing extraction forces evenly along the stem's longitudinal axis. This prevents concentrated stresses that could cause the stem to fracture or the bone canal to collapse. The tool's design ensures that extraction forces are transmitted through the stem rather than applied directly to the surrounding anatomy.
Solution Approach 2:
The same impactor-extractor tool used for installation is inverted and used for extraction. The connector that was driving the stem into the bone during installation now serves to guide the stem's removal. By reversing the tool's orientation and using the same engagement mechanism, the invention ensures that extraction forces follow the same controlled path as installation forces, minimizing damage risk.
3Device complexity
If a single tool is used for both installation and extraction, then instrument inventory is reduced, but the tool must perform multiple functions increasing complexity
Solution Approach 1:
The impactor-extractor is designed as a universal tool that performs both installation and extraction functions. The connector can engage with the stem's drive slot in either orientation, and the lever arm mechanism provides mechanical advantage for both driving the stem into the bone and pulling it out. The tool's symmetry and reversible engagement mechanism allow a single instrument to replace what would traditionally require separate installation and extraction tools.
Solution Approach 2:
The tool incorporates dynamic elements that allow it to adapt its function based on orientation and engagement direction. The lever arm can be positioned on either side of the connector, and the engagement interface can transmit forces in both compression (installation) and tension (extraction) modes. This dynamic adaptability allows the same physical tool to perform opposite functions without requiring structural modifications.
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 impactor-extractor tool facilitates accurate installation and removal of prosthetic stems, reducing the risk of complications and extending the lifespan of the prosthesis by ensuring proper placement and minimizing damage to the implant and surrounding anatomy.
Implementation Method 1
The lever can be pivotable about a first pivot point distal to the impact head of the body
Implementation Method 2
The proximal surface for receiving an impaction force to seat the stem within a canal of the bone
Implementation Method 3
The base can include a first taper connector sized to mate with a second taper connector of the stem
Data Source
AI summary
An impactor-extractor for inserting or extracting a stem of a prosthesis into or from a bone can include a body having a first end and a second end. The body can include an impact head located at the first end. A lever can be connected to the body and pivotable about a first pivot point distal to the first end of the body. A base can be located at the second end of the body and can include a first taper connector sized to mate with a second taper connector of the stem. A lock can be located at and pivotable about a second pivot point proximate the second end and can include an extension configured to secure the stem to the first taper connector. Linkages can connect the lever and the lock.