Fixation Device Apertures and Detents for Bone Fragment Retention
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Solution Overview
Problem
Current methods for repairing complex bone fractures, such as patellar fractures, face challenges with manipulating and securing malleable metal rods or cables, which are stiff and difficult to maneuver, often requiring invasive procedures and leading to complications like infection and further surgeries.
Innovation Solution
A fixation device with a loop mechanism that includes a first and second surface, apertures, channels, and a bridge, allowing for secure anchoring of an implant loop around a bone, facilitating easier manipulation and tensioning, and an adjustable metallic multifilament implant for enhanced flexibility and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If malleable metal rods are used to secure bone fragments, then the fragments can be retained in proper position, but the rods are difficult to manipulate and require invasive procedures
Solution Approach 1:
The fixation device is divided into multiple components: a button portion that anchors to the bone, a rod portion that passes through the bone tunnel, and a locking mechanism with detents. This segmentation allows each component to perform its specific function efficiently while simplifying the overall manipulation process compared to single-piece rod systems
Solution Approach 2:
The rod acts as an intermediary element that connects the button portion to the locking mechanism. It transmits the securing force from the button to the bone fragments while allowing controlled manipulation through the bone tunnel, mediating between the anchoring function and the locking function
2Strength
If malleable metal rods are twisted together to secure them, then torsional resistance is provided, but spare rod material must be cut away leaving a large subcutaneous protrusion
Solution Approach 1:
The locking mechanism uses movable detents that can engage with corresponding features on the rod portion. This dynamic engagement provides torsional resistance through a controlled mechanical interaction rather than permanent twisting, allowing the components to be secured without excessive material removal
Solution Approach 2:
The detents are positioned at specific locations on the rod portion to engage with corresponding features, providing localized torsional resistance exactly where needed. This concentrated locking approach eliminates the need for extensive twisting and material removal along the entire rod length
3Strength
If cables or ropes with large cross section are used, then they can provide sufficient strength, but they are relatively stiff and difficult to manipulate
Solution Approach 1:
The rod portion is designed with a slender, flexible profile that allows it to be easily manipulated through bone tunnels and positioned accurately. Despite its reduced cross-section, it maintains sufficient strength through its material properties and the mechanical advantage provided by the locking mechanism
Solution Approach 2:
The rod's dimensions are optimized to balance flexibility and strength requirements. By changing parameters such as diameter, length, and material properties, the rod achieves the appropriate level of flexibility for manipulation while maintaining the structural integrity needed for bone fixation
4Reliability
If pins are used to secure cables to bone, then the cables can be tensioned, but the pins can be a route for infection and are susceptible to fracture
Solution Approach 1:
The locking mechanism extracts the function of securing the rod to the button portion without requiring pins that penetrate through the skin. The detents engage with the rod internally or at the bone interface, eliminating the external pin tract that serves as an infection route
Solution Approach 2:
The design converts the potential harm of pin insertion (infection risk) into a benefit by using the bone tissue itself as the anchoring medium. The button portion embeds in the bone and the rod secures internally, transforming the infection risk associated with external pins into a secure, infection-resistant internal fixation system
Data Source
AI summary
An implant assembly for use in tissue repairs includes a fixation device and a flexible elongate implant. The fixation device has a body with a first surface adapted to face towards a bone and a second surface adapted to face away from the bone. Apertures extend through the fixation device body from the first surface to the second surface and serve to attach one end of the flexible elongate implant loop. The flexible elongate implant has a multifilament structure comprising filaments which are of a metallic or non-metallic material. The implant is coupled to the fixation device by passing through the apertures, and has a loop having a first end that is secured to the fixation device and a second end which can be releasably coupled to the fixation device following passage through or around a bone, for securing the implant assembly relative to the bone.