Retrograde Cutter System for Minimally Invasive Cartilage Excision
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Solution Overview
Problem
Hyaline cartilage in joints, particularly in knee and hip joints, suffers from damage due to diseases like rheumatoid arthritis and osteoarthritis, leading to compromised articular surfaces and joint function, as existing methods struggle to effectively replace or repair damaged hyaline cartilage with durable alternatives.
Innovation Solution
A cutter system comprising a central shaft and a tiltable cutter that can be rotated and positioned to excise damaged articular surfaces, allowing for minimal invasive procedures by creating an excision site without direct access, using a retrograde or end-on approach with a stop sheath to control the depth and orientation of the excision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional open surgical methods are used to excise damaged articular surfaces, then complete removal of damaged cartilage and creation of implant sites can be achieved, but patient trauma and invasiveness increase significantly
Solution Approach 1:
The patent applies retrograde access by approaching the articular surface from the opposite direction - entering through the joint capsule and bone from the posterior aspect rather than through open anterior exposure. The cutter system is introduced through a small incision and navigates retrograde to reach the damaged cartilage, effectively inverting the traditional surgical approach to minimize trauma while maintaining excision capability
Solution Approach 2:
The invention transitions from two-dimensional open surface access to three-dimensional internal navigation. The cutter system moves through the bone and joint capsule in the third dimension (depth) to reach the articular surface, allowing precise excision without requiring lateral or anterior dissection planes that would increase patient trauma
2Ease of operation
If direct access surgical approaches are used to reach damaged articular surfaces, then complete visualization and treatment are possible, but invasiveness and surgical complexity increase
Solution Approach 1:
The cutter system is nested within a protective sheath that is introduced through a small incision. The cutter can be advanced or retracted within the sheath, allowing the entire assembly to pass through minimal access points. This nesting enables complex cutting functionality to be delivered through simple external access, reducing surgical complexity while maintaining operational ease
Solution Approach 2:
The patent introduces a guide wire and sheath system as intermediaries between the external surgical field and the internal articular surface. These intermediaries facilitate the passage of the cutter system through bone and soft tissue, simplifying the access process while the cutter itself remains a focused, simple cutting instrument at the target site
3Reliability
If conventional cartilage repair methods are used, then healing can occur through fibrocartilage formation, but the durability and functional properties of the repaired tissue are significantly reduced
Solution Approach 1:
The patent applies the extraction principle by completely removing the damaged hyaline cartilage and underlying fibrillated tissue through precise excision. By taking out the damaged tissue entirely rather than attempting to repair it in place, the system creates a clean implant bed that can receive durable hyaline cartilage allograft or autograft tissue, thereby restoring both healing capability and long-term durability
Solution Approach 2:
The invention changes the fundamental parameter of tissue replacement - shifting from in-situ repair (which produces inferior fibrocartilage) to ex-situ preparation followed by implantation of pre-prepared hyaline cartilage grafts. This parameter change in the repair strategy transforms the outcome from durable fibrocartilage to durable hyaline cartilage restoration
Data Source
AI summary
A method for excising a portion of an articular surface using a retrograde procedure. An access tunnel is provided extending through a bone and to the articular surface. A central shaft is inserted through the access tunnel to the articular surface and a cutter is coupled to the central shaft. The cutter is coupled to the central shaft to allow the cutter to rotate with the central and to allow the cutter to be tiltable relative to the central shaft. The cutter is rotated and a retrograde force is applied to the cutter to urge the cutter into the articular surface.