Implantable Passive Mechanisms for Differential Tendon Force Distribution
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Solution Overview
Problem
Current tendon-transfer surgeries limit musculoskeletal function due to coupled finger movement, requiring excessive muscle force and leading to incomplete and unbalanced grasps, as well as decreased knee joint strength post-surgery, due to the inability to preferentially enhance, scale, or distribute muscle force and movement across tendons.
Innovation Solution
Implantable passive engineered mechanisms, such as pulley systems, lever mechanisms, and tendon networks made from biocompatible materials, that separate and differentially apply force across tendons, allowing for individual finger control and improved grasping strength by scaling and distributing muscle force more effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single donor muscle is directly sutured to multiple recipient tendons, then the surgical procedure is simple and direct, but the muscle force and movement cannot be preferentially enhanced, scaled, or distributed across the tendons
Solution Approach 1:
The patent segments the single tendon connection into multiple separate tendon connections by introducing a multi-tendon anchor device with multiple attachment points. This allows the single donor muscle to be differentially connected to multiple recipient tendons, enabling independent force distribution and movement control across each tendon while maintaining surgical feasibility.
Solution Approach 2:
The multi-tendon anchor device serves as an intermediary component between the single donor muscle and multiple recipient tendons. This mediator enables the transformation of single-muscle force into differentially distributed forces across multiple tendons, providing both force scaling and preferential distribution capabilities that neither direct suture nor complex mechanisms alone could achieve.
2Ease of operation
If the suture couples the movement of all four fingers, then the surgical procedure is straightforward, but the fingers cannot adapt naturally to the object shape during grasping
Solution Approach 1:
The patent segments the coupled finger movement into individual finger control by connecting each finger tendon separately to the multi-tendon anchor device. This segmentation allows each finger to move and adapt independently to object shapes during grasping, while the overall surgical procedure remains straightforward through the use of a single anchor device.
Solution Approach 2:
The patent introduces dynamic capability to the finger movement system by allowing differential tensioning and independent movement of each finger tendon through the multi-tendon anchor. This enables the fingers to dynamically adapt to varying object shapes and grasping requirements, transforming the static coupled movement into dynamic independent control.
3Productivity
If one finger makes contact with an object while other fingers are still closing, then the grasping process begins, but further muscle contraction forces the contacted finger to curl further and slip on the object
Solution Approach 1:
The patent applies local quality control by enabling independent force distribution to each finger tendon through the multi-tendon anchor device. This allows the system to locally adjust the force and movement of each finger based on its contact status with the object, preventing the contacted finger from slipping while maintaining closure of other fingers.
Solution Approach 2:
The patent implements feedback control by allowing the differential tendon connections to respond to individual finger contact forces. When one finger contacts the object, the system can detect the force change and adjust the tension distribution through the multi-tendon anchor to prevent further curling and slipping, while continuing to close other fingers.
4Productivity
If the muscle has to stretch the tendon of the finger that has already made contact in order to flex the other fingers, then the grasping process continues, but the muscle force requirement increases
Solution Approach 1:
The patent segments the muscle force into separate controllable components for each finger tendon through the multi-tendon anchor device. This segmentation eliminates the need for the muscle to isometrically stretch already-contacted tendons, as each tendon can be independently tensioned and controlled, thereby reducing the overall muscle force requirement while completing the grasping process.
5Ease of manufacture
If tendon tensioning has even a 5% error, then the surgical procedure is completed, but the finger movement would be either premature or delayed during the grasping process
Solution Approach 1:
The patent applies preliminary action by allowing individual tendon tensioning and adjustment through the multi-tendon anchor device before the actual grasping function is required. This preliminary adjustment capability compensates for surgical tensioning errors, enabling precise finger movement timing to be established during the surgical procedure itself, thereby eliminating premature or delayed finger movement during grasping.
Data Source
AI summary
Implantable passive engineered mechanisms and a method for implanting such devices in a subject are described. The implantable passive engineered mechanism may be made of or comprise a biocompatible material and is appropriately sized for implantation in a subject. Exemplary implantable passive engineered mechanisms may be selected from a strut, a pulley, a lever, a compliant mechanism, a scissor lift, a tendon network, springs, planetary gears, rigid or soft hydraulics, a linkage system, a cam/clutch system, or combinations thereof. In some embodiments the system comprises plural inserts, such as pulleys, levers, and/or tendon networks. Plural inserts may be arranged hierarchically to distribute force differentially from an input to one or more outputs.