Variable Height Guide Element for Ligament Reconstruction
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Solution Overview
Problem
Conventional elongate guide elements used in ligament and tendon reconstruction are prone to fracturing under high forces during patient rehabilitation, and increasing their size to counteract this would require larger tunnels and make implantation more difficult, potentially leading to bone resorption and other complications.
Innovation Solution
A strengthened elongate guide element with a progressive height increase towards an intermediate section, formed via metal injection molding (MIM) process, featuring support apertures and a saddle design to securely couple the implant, reducing the likelihood of damage and lodging during implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the size of the guide element is increased to prevent fracturing under high forces, then the strength and reliability are improved, but the device complexity and difficulty of implantation increase, potentially causing bone resorption
Solution Approach 1:
The guide element features a progressive height increase towards an intermediate section, creating non-uniform thickness distribution. This local quality variation concentrates material where strength is most needed (intermediate section) while maintaining smaller dimensions at the ends, resolving the contradiction between overall strength and device size complexity
Solution Approach 2:
The guide element transitions from a uniform cross-section to a variable cross-section with progressive height increase in the intermediate section. This dimensional change adds structural complexity only where necessary to withstand high forces during rehabilitation, rather than uniformly increasing the entire device size
2Reliability
If the guide element size is increased to prevent fracturing, then the reliability is improved, but the ease of operation deteriorates as larger tunnels are required for implantation
Solution Approach 1:
The progressive height increase creates a tapered profile where the intermediate section is thicker for strength while the ends remain smaller for easier implantation. This local quality differentiation allows the guide element to be pulled through smaller bone tunnels while maintaining sufficient strength to prevent fracturing during rehabilitation
Solution Approach 2:
By varying the cross-sectional dimensions along the length of the guide element, the design optimizes the balance between implantation ease and post-implantation reliability. The progressive height increase ensures the guide element can withstand rehabilitation forces without requiring uniformly large dimensions throughout
3Strength
If the guide element size is increased to prevent fracturing, then the strength is improved, but harmful factors increase due to potential bone resorption and complications
Solution Approach 1:
The non-uniform thickness distribution with progressive height increase concentrates material where mechanical strength is critical (intermediate section) while minimizing material contact with bone at the ends. This reduces the surface area potentially causing bone resorption while maintaining sufficient strength to prevent device fracturing that would also harm the patient
Data Source
AI summary
The invention relates to an elongate guide element (22) for guiding an implant (1) along a tunnel (17) in a bone (12, 14) and for securing the implant within the tunnel. One exemplary guide element comprises: first end and second ends (24, 26); a pair of support apertures (42) for receiving a support element (3) for the implant, the support apertures being spaced apart in a direction along a main longitudinal axis (28); a saddle (46) extending transverse to the longitudinal axis, one of the pair of support apertures being disposed between the saddle and the first end and the other between the saddle and the second end. The support element extends through one of the pair of support apertures, at least partly around the saddle and then through the other aperture. The guide element has a generally planar bone facing surface (48) and a second opposite surface (50). The guide element has a height, measured in a direction from the planar surface towards the second surface, the height increasing in a direction from the first and second ends towards an intermediate section of maximum height (H). At least part of the saddle is disposed within the intermediate section and defines a space (54) between the second surface and a maximum height extent of the saddle, for receiving part of the support element.