Intramedullary Stem Extraction Tool Leverage Mechanism
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Solution Overview
Problem
Current methods for removing intramedullary stem implants from bones often result in unintended damage to surrounding bone and soft tissue, leading to longer surgery times, increased recovery periods, and higher risks of infection due to inadequate techniques for breaking cement or bone integration.
Innovation Solution
A modular handheld lever system with interchangeable attachments that provides a customized grip for the implant, leveraging a mechanical advantage to efficiently separate the implant from its cement or bone bond, minimizing the need for high-impact forces and reducing tissue trauma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high-impact forces are used to break cement or bone integration, then the implant can be removed, but surrounding bone and soft tissue are damaged
Solution Approach 1:
The extraction tool divides the force application into multiple controlled segments: the osteotome blade segments the cement-bone interface, the lever provides mechanical advantage segmentation, and the force is applied in controlled increments rather than single high-impact strikes. This segmentation allows gradual separation without transmitting damaging forces to surrounding tissue.
Solution Approach 2:
The osteotome blade acts as an intermediary between the applied force and the cement-bone interface. Instead of applying force directly to break the bond (which causes tissue damage), the blade inserts into the interface and gradually pries apart the cement and bone, mediating the separation process to avoid harmful impact forces.
2Loss of time
If existing extraction methods are used, then implant removal is attempted, but surgery time is prolonged
Solution Approach 1:
The osteotome blade is inserted into the cement-bone interface before applying extraction force, preliminarily creating a separation path. This preliminary action prevents the need for repeated high-impact strikes that would prolong surgery, as the interface is already prepared for clean separation.
Solution Approach 2:
The tool combines static leverage (from the lever mechanism) with dynamic prying action (from the osteotome blade). The blade can be inserted and adjusted dynamically at the interface while the lever provides stable mechanical advantage, allowing efficient extraction without prolonged surgery time.
3Area of stationary object
If bone is removed to expose the implant, then the implant can be accessed, but bone stock is depleted requiring allograft
Solution Approach 1:
The osteotome blade applies force locally at the cement-bone interface rather than requiring broad bone removal. The blade inserts precisely where needed to separate cement from bone, maintaining local bone quality and stock while achieving implant exposure and removal without extensive bone resection.
4Reliability
If vertical osteotomy is performed to envelope the implant, then extraction is achieved, but infection risk and fracture risk increase
Solution Approach 1:
The osteotome blade extracts the cement from the bone interface by inserting it into the cement-bone junction and prying the cement away. This extraction method avoids the need for vertical osteotomy that would envelope the implant, thereby eliminating the associated infection and fracture risks while maintaining effective extraction.
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 tool effectively breaks implant stems free from their cement mantle with reduced risk of bone or tissue damage, shortening surgery time and recovery, while allowing for precise customization to various implant geometries and sizes, thus minimizing complications.
Implementation Method 1
levering action to provide a mechanical advantage that facilitates separation of the implant from its cement or bone bond
Data Source
AI summary
The present disclosure provides an implant extraction tool for removing either cemented or non-cemented intramedullary stem implants from bones. The tool includes an elongated handle section having proximal and distal end sections with a cap section affixed to the distal end section of the elongated handle section, and cap section has a hole extending therethrough. The tool includes an attachment member having opposed ends, one of these opposed ends is configured to grip a cemented or non-cemented intramedullary implant stem in a bone. The attachment member has a size and shape to be received into the hole and the other of opposed end includes at least one hook feature for gripping the implant. The tool includes an elongated lever having an elongate proximal section and a shorter distal end section with a pivot fulcrum at a transition from the distal end section to the elongate proximal section. The distal end section is configured to engage the hook feature of the attachment when proximal end sections of the elongated handle section and the elongated lever are squeezed towards each other such that upon squeezing the attachment member is levered out of the hole in the cap section to effect removal of the stem implant.