Open-Network Fixation Implants Resist Sacroiliac Joint Rotation
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Solution Overview
Problem
Conventional bone screw implants for the sacroiliac joint are vulnerable to rotation and failure due to the natural movement of the joint, leading to instability and hypermobility, which complicates diagnosis and treatment of sacroiliac dysfunction.
Innovation Solution
Development of fixation implants with an open network body resembling trabecular bone structure, featuring enhanced bone engagement surfaces and osseo-integration through open cores, such as helical bodies or truss arrangements, to provide increased stability and resistance to rotational motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bone screw implants are used in the sacroiliac joint, then the joint can be fixed, but the implants are vulnerable to rotation and failure due to natural joint movement
Solution Approach 1:
The implant incorporates a dynamic polyaxial locking mechanism that allows controlled movement and adjustment. The locking mechanism can transition between locked and unlocked states, enabling the implant to adapt to natural joint motion while maintaining stability when needed, thereby resolving the contradiction between allowing physiological movement and preventing pathological hypermobility
Solution Approach 2:
The implant changes its mechanical parameters through the polyaxial locking mechanism, which can alter the degree of freedom and rigidity of the fixation system. By adjusting the locking state, the implant can transition from a more flexible state during insertion to a rigid stable state during healing, addressing both the need for initial adaptability and long-term stability
2Ease of manufacture
If typical bone screw type implants are used, then fixation can be achieved, but they are vulnerable to rotation and ultimate failure
Solution Approach 1:
The implant introduces an additional dimensional control mechanism through the polyaxial locking system, which controls the orientation and angular position of the fixation elements. This adds a rotational degree of freedom control that prevents unwanted rotation while maintaining the basic screw fixation function, thereby improving reliability without significantly complicating the manufacturing process
3Strength
If fixation implants provide stable fixation, then bone purchase is enhanced, but the complexity of the implant structure increases
Solution Approach 1:
The implant is divided into distinct functional segments: the polyaxial locking mechanism, the fixation elements, and the bone engagement surfaces. This segmentation allows each component to be optimized independently for its specific function while maintaining overall structural integrity, enabling enhanced bone purchase without proportionally increasing overall device complexity
Data Source
AI summary
A fixation implant includes a head, a shank and a distal tip, and one or more of the head, shank and distal tip may be cannulated. The shank includes a threaded ingrowth portion extending from the head to the tapered distal tip that includes external threads, and at least one open network body extending along the length of the ingrowth portion. The open network body selected from one or a combination of a helix, an arrangement of trusses, a scaffold of open and interconnected pores, a porous framework of random open and interconnected pores, and combinations of these.