Friction-Fit Spinal Implant Receiver Assembly for Stable Screw Alignment
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Solution Overview
Problem
Traditional receiver assemblies for bone fasteners in spinal fixation surgeries are cumbersome to assemble due to the need for preselection and alignment, often requiring special tools and trained technicians, and are prone to drooping or slipping out of alignment during implantation.
Innovation Solution
A friction-fit mechanism between the receiver and fastener, facilitated by ridges and protrusions, provides a stable orientation before locking with a set screw, allowing modular assembly and reducing alignment issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional receiver assemblies are preassembled by the manufacturer, then assembly precision is improved, but device complexity increases and surgical flexibility decreases
Solution Approach 1:
The receiver assembly is divided into separable components (receiver body, fastener, locking mechanism) that can be independently selected and assembled during surgery, eliminating the need for preassembly while maintaining precision through modular design features like friction-fit interfaces and alignment guides
Solution Approach 2:
The receiver assembly incorporates self-aligning and self-locking features that enable surgical staff to assemble the components without specialized training or tools, with the friction-fit mechanism automatically providing stable engagement and the locking mechanism automatically securing the joint when activated
2Reliability
If receivers are oriented in alignment for rod insertion, then connection reliability is improved, but alignment stability deteriorates due to drooping and slipping
Solution Approach 1:
The friction-fit mechanism between the fastener head and receiver body is designed to automatically engage and stabilize the relative orientation of components during the insertion process itself, before final rod connection, preventing drooping and slipping without requiring pre-alignment adjustments
Solution Approach 2:
The friction-fit interface acts as an intermediary mechanism between the fastener and receiver, providing temporary but stable alignment maintenance during surgery, with the frictional force serving as the mediating force that prevents movement until the locking mechanism is activated
3Reliability
If multiple receiver assemblies are used to secure vertebrae, then fixation reliability is improved, but surgical time increases due to alignment complexity
Solution Approach 1:
The standardized friction-fit receiver assembly design allows the same component to be used across multiple vertebrae with consistent alignment characteristics, enabling surgeons to efficiently replicate the same assembly configuration throughout the spine without recalibration or complex alignment procedures for each level
Solution Approach 2:
The friction-fit mechanism provides optimal engagement force parameters that automatically maintain alignment stability, allowing rapid assembly at multiple levels without requiring time-consuming adjustment of alignment parameters for each receiver
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 friction-fit mechanism stabilizes the receiver's orientation, simplifies assembly, and allows for pre- or intra-operative selection of components, enhancing surgical efficiency and reducing alignment complications.
Implementation Method 1
a frictional force can be applied between a screw head and a retention ring, and another frictional force can be applied between the screw head and a pressure insert. The frictional force and contact maintains and stabilizes an orientation of a receiver relative to the screw head
Data Source
AI summary
Implantable devices and assemblies that provide a friction fit between a receiver and a fastener, such as a bone screw. A frictional force is applied between the screw head and both a retention ring and a pressure insert, maintaining and stabilizing the orientation of the receiver relative to the screw head before being fixed by a set screw. This mechanism prevents drooping or slipping of the receiver out of alignment when implanted. Additionally, the devices allow for modular assembly before or during spinal fixation, enabling bottom-side loading of the screw head into the receiver. Various screws with different characteristics can be coupled to the receiver body before or after implantation. The frictional force may be facilitated by one or more ridges on the receiver body that engage the pressure insert, which is resiliently urged against the screw head, providing a spring-like compression force.