Bone Plate Captive Clips for Spinal Fixation Angulation
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Solution Overview
Problem
Current orthopaedic fixation systems lack the ability to allow post-operative angulation and movement, particularly in spinal applications, where vertebral bodies need to compress over grafts, and there is a need for a system that facilitates translational and rotational settling while resisting fastener back-out.
Innovation Solution
A fixation system comprising a plate with undercut fixation holes and resilient clips that permit fastener motion, including sliding and toggling, while preventing back-out, through the use of specifically designed fasteners with perimetral grooves and instrument receiving portions that interact with the clips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid fixation system is used to secure fasteners to the bone plate, then the fasteners are firmly anchored, but post-operative angulation and movement are prevented
Solution Approach 1:
The fixation system transitions from a static rigid connection to a dynamic adjustable connection. The fastener head can rotate within the bushing, and the bushing itself can rotate within the plate hole, allowing the system to adapt its configuration post-operatively while maintaining secure anchoring.
Solution Approach 2:
The fixation system is divided into multiple independently rotatable components: the fastener head, the bushing, and the plate hole. Each component can rotate relative to the others, enabling cumulative angular adjustment while maintaining firm anchoring at each interface through friction and geometric constraints.
2Adaptability or versatility
If a bushing is used to permit polyaxial movement of the fastener, then post-operative angulation is enabled, but the fastener may back out from the plate
Solution Approach 1:
The system proactively prevents fastener back-out by creating friction resistance through the friction fit between the fastener shaft and bushing, and between the bushing and plate hole. This frictional engagement acts as a preliminary counter-force to any back-out tendency, securing the fastener before removal can occur.
Solution Approach 2:
The bushing serves as an intermediary component between the fastener and the plate hole. It mediates the connection by providing both rotational freedom and friction-based retention, allowing angular movement while preventing back-out through its friction fit with both the fastener shaft and the plate hole.
3Reliability
If the fastener is rigidly fixed in the plate hole, then back-out is prevented, but translational and rotational settling is blocked
Solution Approach 1:
The system allows dynamic adjustment through multiple rotational degrees of freedom. The fastener head can rotate relative to the bushing, and the bushing can rotate relative to the plate hole, enabling translational and rotational settling to occur naturally post-operatively while friction fits prevent complete back-out.
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
Enables post-operative angulation and movement of fasteners, facilitating vertebral body compression and resisting back-out, thereby improving the stability and effectiveness of spinal fixation.
Implementation Method 1
at least one resilient clip is disposed in at least a portion of the undercut
Implementation Method 2
The at least one fastener comprises a head and a threaded shaft
Data Source
Figure 1A~1E
Figure 2A~2B
Figure 3
AI summary
A fixation system includes a plate comprising a top surface, a bottom surface, a central longitudinal axis, at least one fixation hole extending between the top and bottom surfaces and comprising an undercut therein, and at least one passage intersecting one of the undercuts. At least one resilient clip is disposed in at least a portion of the undercut, with the at least one clip having a pair of generally parallel sides and an end tab. At least one fastener is provided and comprises a head and a threaded shaft, with the head comprising a perimetral groove extending around at least a portion thereof and an instrument receiving portion. The at least one clip is configured and dimensioned to seat in the undercut with the end tab extending within the passage, and the at least one fastener is configured and dimensioned to be received in the at least one fixation hole and securable therein when the at least one clip abuts the perimetral groove of the head.