Expandable Bone Tunnel Fixation for ACL Grafts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for securing soft tissue grafts during ACL reconstruction face issues such as graft damage from sharp screw edges, inaccurate graft sizing, prolonged recovery with autograft harvest, visibility and discomfort from external fixation devices, and suboptimal tensioning due to resilient anchoring points.
Innovation Solution
An expandable member system with a delivery structure that injects a flowable medium to expand and secure the graft within a bone tunnel, optionally combined with a bone screw for compression and a longitudinal sleeve member with a pin for outward expansion, ensuring proper seating and tensioning of the graft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If interference screw is used to secure bone graft in tunnel, then fixation is achieved, but graft may be cut or frayed by sharp edges of screw
Solution Approach 1:
The patent introduces an intermediary protective mechanism where the interference screw is equipped with a protective covering or modified surface that prevents direct contact between sharp edges and the graft. This mediator protects the graft from cutting or fraying while still allowing the screw to secure the graft firmly in the tunnel.
Solution Approach 2:
The patent modifies the physical parameters of the interference screw, specifically changing the surface characteristics of the screw edges from sharp to rounded or coated surfaces. This parameter change reduces the harmful cutting effect on the graft while maintaining the screw's ability to provide secure fixation.
2Strength
If interference screw or bone graft is oversized versus tunnel size, then fixation strength increases, but too much force is exerted on graft causing damage
Solution Approach 1:
The patent employs a dynamic interference screw design that allows controlled adjustment of the interference level. The screw can be inserted with initial interference to provide strong fixation, but the system allows for controlled relaxation or adjustment to prevent excessive force from damaging the graft, achieving a dynamic balance between fixation strength and graft protection.
Solution Approach 2:
The patent applies partial interference rather than complete oversizing. The interference screw is designed to provide just enough interference to achieve secure fixation without the excessive force that would damage the graft. This partial action principle optimizes the balance between achieving sufficient fixation strength and avoiding graft damage.
3Reliability
If external staple or screw and washer assembly is used to secure graft, then fixation is achieved, but components are visible and cause patient discomfort
Solution Approach 1:
The patent places the fixation components inside the bone tunnel rather than on the external surface. The interference screw is nested within the tunnel, and the graft is secured internally. This nesting approach eliminates visible external components while maintaining secure fixation, thereby removing the source of patient discomfort and cosmetic concerns.
4Reliability
If staple or screw and washer assembly is used for securement, then fixation is achieved, but securement may slip providing non-optimum tension
Solution Approach 1:
The patent replaces the mechanical staple or washer system with an interference-based mechanical system. The interference screw creates friction-based anchoring within the tunnel that prevents slippage. This substitution eliminates the slippage problem inherent in staple and washer systems while maintaining secure fixation and optimal graft tension.
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 system effectively secures soft tissue replacements within bone tunnels, reducing graft damage, minimizing recovery time, enhancing patient comfort, and providing stable, optimal tensioning without the need for additional surgeries.
Implementation Method 1
The delivery structure is adapted to inject a flowable medium into the expandable member thereby expanding the expandable portion and urging the soft tissue replacement into a bone surface
Implementation Method 2
An expandable member system with a delivery structure that injects a flowable medium to expand and secure the graft within a bone tunnel, optionally combined with a bone screw for compression
Data Source
AI summary
A system and method to assist in securing a soft tissue replacement in a bone tunnel includes an expandable member having an opening and an expandable portion. A delivery structure includes a connection portion selectively coupled to the opening of the expandable member. The delivery structure is adapted to inject a flowable medium into the expandable member thereby expanding the expandable portion and urging the soft tissue replacement into a bone surface defining the bone tunnel.