Prosthetic Liner Tendon Flexion Enhancement
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Solution Overview
Problem
Conventional prosthetic and orthotic liners and sleeves often require complex multi-part molds to reduce material bunching, increasing labor and material costs, and stability issues lead to higher rejection rates and impaired flexion around joints.
Innovation Solution
A prosthetic or orthotic liner with an elastomeric tubular member and a tendon made of higher durometer material, integrally molded within, to enhance flexion by contracting and reducing material accumulation behind joints, using a two-part mold setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If bent male and female molds with three or more parts are used to pre-flex the liner, then material bunching behind the knee is reduced, but labor and material costs increase and mold stability decreases
Solution Approach 1:
The liner is segmented into two functional components: a tubular body portion and a separate flexion enhancement member (tendon). This segmentation allows the tendon to be independently positioned and molded into the tubular member, enabling flexion enhancement without requiring complex multi-part molds. The tendon acts as a discrete element that can be integrated during a single molding process.
Solution Approach 2:
The flexion enhancement member (tendon) serves as an intermediary element that mediates between the mold structure and the final liner shape. By positioning the tendon within the mold cavity before injecting elastomeric material, the tendon acts as a temporary form-giving element that creates the desired flexion characteristics in the final product without requiring complex mold geometry.
2Shape
If three or more part molds are used, then liner flexion is improved, but rejection rate increases due to stability issues
Solution Approach 1:
The liner is segmented into two functional components: a tubular body portion and a separate flexion enhancement member (tendon). This segmentation allows the tendon to be independently positioned and molded into the tubular member, enabling flexion enhancement without requiring complex multi-part molds. The tendon acts as a discrete element that can be integrated during a single molding process.
Solution Approach 2:
The flexion enhancement member (tendon) serves as an intermediary element that mediates between the mold structure and the final liner shape. By positioning the tendon within the mold cavity before injecting elastomeric material, the tendon acts as a temporary form-giving element that creates the desired flexion characteristics in the final product without requiring complex mold geometry.
3Ease of manufacture
If conventional elastomeric material is used without flexion enhancement, then manufacturing is simple, but material bunching occurs behind the knee during flexion
Solution Approach 1:
The elastomeric material exhibits local quality variations through the integration of the tendon. The tendon creates a localized region of different mechanical properties (higher durometer hardness) within the softer elastomeric matrix. This local quality difference enables the liner to resist bunching in specific areas (behind the knee) while maintaining overall flexibility and comfort elsewhere.
Solution Approach 2:
The liner becomes a composite structure combining two elastomeric materials with different properties: the base tubular member material and the tendon material (higher durometer hardness). This composite construction allows the softer base material to provide comfort and flexibility while the harder tendon provides structural support to prevent material accumulation, achieving both comfort and functional performance.
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 solution allows for enhanced flexion around joints while maintaining a two-part mold simplicity, reducing material bunching and labor costs, and improving the fit and comfort of prosthetic devices.
Implementation Method 1
a tendon (14) attached along a portion of the tubular member (12) to urge the elastomeric material at such portion of the tubular member (12) to contract
Implementation Method 2
The elastomer forming the liner or sleeve frictionally engages and remains attached to the skin of a residual limb so that the limb is retained within the prosthetic socket
Data Source
AI summary
The liner or sleeve is for use around a joint, for example, as a skin interface between a limb and a prosthetic or orthotic device. The liner or sleeve includes an elastomeric material defining a tubular member to be positioned around a joint. A tendon is attached along a portion of the tubular member to urge the elastomeric material at such portion of the tubular member to contract. The tendon may be integrally molded within the portion of the tubular member. The tendon may be formed of an elastomeric material having a higher durometer hardness relative to the durometer hardness of the tubular member elastomeric material. With the present approach, it is possible to maintain the use of a two part mold while providing a liner or sleeve with enhanced flexion adjacent to a joint area.