Low-profile uniplanar bone screw with rocker mechanism
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Solution Overview
Problem
Conventional uniplanar bone screws used in orthopedic surgeries, particularly for scoliosis, are bulky and cause discomfort and irritation to patients, often necessitating a second surgery for removal due to their large size and limited adjustability.
Innovation Solution
A low-profile uniplanar bone screw design featuring a rocker mechanism that allows for adjustable rod positioning within a single plane without requiring a movable screw head, reducing bulkiness and enhancing adjustability while maintaining uniplanar movement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional polyaxial or uniplanar screws are used to provide adjustability for rod positioning, then the screw can accommodate variations in screw placement and alignment, but the screw becomes larger and bulkier, causing pain and irritation to patients
Solution Approach 1:
The invention divides the screw head into separate functional components: a fixed base portion and a movable rod-receiving portion (rocker). This segmentation allows the rod-positioning function to be isolated in a small rocker mechanism rather than requiring a large movable head, thus providing adjustability while minimizing overall screw size and bulkiness.
Solution Approach 2:
The invention transitions from conventional polyaxial screws that allow multi-directional movement to a uniplanar design that constrains movement to a single plane. By limiting the degree of freedom to one plane (cranial/caudal angulation only), the screw achieves sufficient adaptability for scoliosis correction while dramatically reducing the size and complexity of the adjustment mechanism.
2Adaptability or versatility
If conventional uniplanar screws are used to provide uniplanar adjustment capability, then the screw can accommodate cranial or caudal angulation, but the screw remains bulky due to the single plane swivel mechanism
Solution Approach 1:
The screw head is segmented into a fixed base and a small rocker component. The rocker is a compact arc-shaped element that provides the uniplanar swiveling motion within a minimal space, eliminating the need for a large-scale swivel mechanism while maintaining full uniplanar adjustment capability.
Solution Approach 2:
The invention introduces a dynamic rocker mechanism that can pivot within a confined arc (e.g., ±15 degrees) to accommodate cranial or caudal angulation. This dynamic element provides the necessary adjustability within a single plane while keeping the overall screw profile low and compact.
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 low-profile design minimizes patient discomfort by reducing bulkiness while providing sufficient adjustability for cranial or caudal angulation, potentially eliminating the need for a second surgery by offering improved fit and reduced irritation.
Implementation Method 1
The rod-securing element includes a fulcrum serving as an axis of rotation about which the rod rotates
Data Source
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AI summary
A bone screw that is a low-profile, uniplanar bone screw is provided. The bone screw is for adjusting a position of a rod. The bone screw includes a main body, a rocker and a rod-securing element. The main body has a shaft with a threaded part. The rocker is coupled to and moveable relative to the main body. The rocker is configured to at least partially receive the rod. The rod-securing element is configured to secure the rod between the rocker and the rod-securing element and relative to the main body. The rod-securing element includes a fulcrum serving as an axis of rotation about which the rod rotates.