Bone Plate Retainer Nesting for Screw Back-Out Prevention
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Solution Overview
Problem
Existing bone plate systems face issues with screw back-out, inadequate control over compression and movement between vertebrae, and discomfort due to rough surfaces and excessive thickness, which can compromise bone fusion and alignment.
Innovation Solution
The bone plate system incorporates screw retainers with straight side portions to prevent back-out, dynamically adjustable plates with elongated bores and retainers to allow controlled translation, and design features to minimize surface interference with surrounding tissues, including recesses and tab portions for secure retainer placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If screw retainers with straight side portions are added to prevent screw back-out, then screw retention reliability is improved, but device complexity increases
Solution Approach 1:
The retainer is nested within the bone plate structure, with the retainer body positioned in a recess of the plate and the straight side portions extending through the plate aperture. This nesting approach allows the retainer to be integrated into the plate without adding significant external complexity, while still providing effective screw retention through the straight side portions that contact the screw shaft.
2Adaptability or versatility
If elongated bores are used to allow controlled translation between vertebrae, then adaptability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The bone plate incorporates elongated bores that allow dynamic adjustment and controlled translation between vertebrae. The elongated geometry provides a range of motion along the longitudinal axis, enabling the system to adapt to physiological movements and settling while maintaining stable fixation. This dynamic capability is achieved through the elongated bore design that permits controlled movement without compromising overall structural integrity.
3Object-affected harmful factors
If plate thickness is reduced to minimize surface interference, then patient comfort is improved, but structural strength decreases
Solution Approach 1:
The bone plate design incorporates local quality variations through strategic placement of reinforcement features. The plate includes raised portions and recesses that concentrate material where structural strength is needed (at screw aperture locations and along load-bearing paths) while maintaining thinner sections in areas where patient comfort is prioritized. This localized quality differentiation allows the plate to provide both structural integrity and reduced surface interference.
Solution Approach 2:
The bone plate utilizes composite construction with varying material densities and configurations. The plate includes both thicker reinforced sections for structural strength and thinner sections for patient comfort, creating a composite structure that optimizes both strength and comfort requirements. The raised portions and recesses create a composite geometry that distributes structural demands across different plate regions.
4Measurement precision
If multiple retainers are added to control movement at multiple levels, then control precision is improved, but device complexity increases
Solution Approach 1:
The bone plate system divides movement control into discrete segments by placing individual retainers at specific vertebral levels. Each retainer independently controls translation at its location, allowing precise control of movement at each level while maintaining simplicity of the overall system. The segmentation approach enables controlled translation at multiple levels without requiring a complex integrated control mechanism.
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 effectively prevents screw back-out, enhances control over compressive forces between vertebrae, and reduces patient discomfort by ensuring a smoother surface contact, thereby improving bone fusion and alignment outcomes.
Implementation Method 1
a retainer (100) preset in the bore (24) to prevent back-out of a screw (22)
Implementation Method 2
The plate (20) includes at least one elongated bore (40) that permits translation of a screw (22) secured with a bone (12)
Implementation Method 3
A portion of the plate (20) is deformed over the open end portion (512) in the recess (90) to capture the end of the retainer (500)
Data Source
AI summary
Bone plate systems and retainers are provided for surgical implants and bone repair. The bone plate is multi-tiered for receiving bone anchors or screws for securing multiple bones or bone fragments in a desired relationship. The plate includes bores for receiving the screws, and the bores may permit and define a translation path for the screws relative to the plate. The retainers are held in a recess in the bores to prevent screw back-out. Once the screw is seated with the plate, the retainer rests over a top surface of the screw to impede screw back-out from the plate. The retainer may expand to permit driving a screw therethrough and may contract once the screw is seated within the plate so the retainer is in a configuration for preventing back-out. Tools and methods are also provided for implantation and removal of the plates and the screws.