Knee Joint Distractor With Natural Motion and Cartilage Unloading
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Solution Overview
Problem
Current treatments for traumatic injuries and pathological conditions of the knee joint, such as osteoarthritis and fractures, often immobilize the joint, leading to reduced motion and adverse effects on soft tissues, while existing external devices do not accurately mimic the complex physiological motion of the knee joint.
Innovation Solution
An external load-bearing distracting device for the knee joint that allows natural motion and unloads the cartilage by distracting the joint, using biocompatible materials with elastic properties, and is anchored to the femur and tibia to provide six degrees of freedom of motion, including longitudinal rotation, while being adjustable to mimic the knee's natural range of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If immobilization is used to treat knee joint injuries, then soft tissue repair is facilitated, but subsequent joint motion is reduced
Solution Approach 1:
The external linkage device incorporates a dynamic knee joint mechanism that replicates the six degrees of freedom of natural knee motion. This allows the joint to move physiologically while being supported by the external framework, enabling motion during the healing period without compromising soft tissue repair
Solution Approach 2:
The external linkage acts as an intermediary structure that bears the mechanical load of the knee joint, allowing the internal soft tissues to heal while the device maintains joint alignment and enables controlled motion. The linkage transfers stresses from the healing tissues to the external framework
2Ease of operation
If external linkages are used to maintain joint motion, then joint mobility is preserved, but they provide only approximate motion not compatible with internal structure requirements
Solution Approach 1:
The device employs a dynamic mechanism that replicates the six degrees of freedom of natural knee motion including flexion-extension, abduction-adduction, rotation, and translation. This dynamic replication ensures accurate motion transmission to the internal joint structures while maintaining external support
Solution Approach 2:
The linkage incorporates adjustable parameters including link lengths, joint centers, and motion ranges that can be customized to match the specific patient's anatomy and physiological motion characteristics, ensuring precise replication of individual knee kinematics
3Reliability
If the knee joint is distracted to unload cartilage, then cartilage regeneration is enabled, but joint stability is reduced
Solution Approach 1:
The external linkage provides counterbalancing support forces that compensate for the destabilizing effect of joint distraction. The framework maintains joint alignment and prevents excessive movements while the distraction force remains applied, ensuring stability during the regeneration period
Solution Approach 2:
The device maintains continuous distraction force application throughout the healing period, keeping the joint surfaces separated to promote cartilage regeneration. The continuous support from the external linkage ensures stability is maintained throughout this extended period
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 device enables natural motion of the knee joint, reduces stress on bones, and allows cartilage regeneration by distracting the joint, preventing subsequent motion reduction, suitable for treating osteoarthritis and fractures.
Implementation Method 1
a first rotatable threaded rod (107); a second rotatable threaded rod (108)... The first translational tube (106) is slidably arranged around the first rotatable threaded rod (107), and the second translational tube (103) is slidably arranged around the second rotatable threaded rod (108)
Implementation Method 2
a rotating joint (117) joining the first and second rotatable threaded rods (107, 108)... the rotating joint (117) being configured to enable natural motion present in the articulating anatomical joint
Implementation Method 3
a first adjustment clamping nut (115) provided on the first rotatable threaded rod (107)... and a second adjustment clamping nut (115') provided on the second rotatable threaded rod (108)... the first adjustment clamping nut (115) is positioned between the rotating joint (117) and a proximal end of the first translational tube (106) such that a longitudinal displacement of the first translational tube (106), towards the rotating joint (117), relative to the first rotatable threaded rod (107) is limited by a contact between the first adjustment clamping nut (115) and the proximal end of first translational tube (106)
Data Source
AI summary
An external load bearing distracting device, which can be positioned to fully unload a knee joint cartilage while providing the knee joint normal motion, for an articulating anatomical joint. The device includes a first and second rotatable threaded rods arranged longitudinally on opposite sides of a rotating joint, and first and second translational tubes slidably arranged around the first and second rotatable threaded rods, respectively. The rotating joint may comprise a ball-and-ring-joint configured for accommodating a two mutually complementary brake elements. The first and second rotatable threaded rods each include a first and second clamping nuts thereon, which contact a proximal end of the first and second translational tube to limit longitudinal translation thereof towards the rotating joint. The distracting device is intended for temporary implantation to treat osteoarthritis, focal cartilage defects, and fractures inside the knee joint.