Multi-Axis Spinal Screw Connection for Angled Load Transfer
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Solution Overview
Problem
Current internal spinal fixation systems face challenges in effectively transferring load from the spinal column to stabilizers, particularly in the cervical region, due to the need for angled screw placement and spacing that is not adequately addressed by existing technologies, leading to instability and complications.
Innovation Solution
A multi-axis connection system that allows screws to be oriented at various angles relative to the plate, with a hole design featuring a smaller aperture and larger central portion to securely lock the screw head, enabling effective load transfer while accommodating unique anatomical and pathological factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If screws are placed at fixed angles and intervals in traditional spinal stabilizers, then the device structure is simple, but it cannot accommodate varying anatomical and pathological factors requiring angled and spaced screw placement
Solution Approach 1:
The hole design allows the screw head to move dynamically within the central portion while being constrained by the aperture, enabling angled placement while maintaining structural integrity. This dynamic capability accommodates varying anatomical requirements without requiring multiple fixed-position holes.
Solution Approach 2:
The invention adds a dimensional aspect to screw placement by allowing angular orientation within the hole structure. The screw can be positioned at different angles relative to the plate while still being retained by the aperture-central portion design, transforming a single-axis placement system into a multi-axis system.
2Ease of operation
If the aperture diameter is made larger to allow screw insertion, then screw placement is easier, but the screw head cannot be securely locked to resist movement
Solution Approach 1:
The hole is segmented into two distinct functional zones: the aperture for screw insertion and the larger central portion for screw head retention. This segmentation allows the aperture to be sized for easy insertion while the central portion provides secure locking, resolving the contradiction between ease of operation and retention security.
Solution Approach 2:
The screw head is nested within the central portion of the hole, which itself is defined by the aperture. This nested structure allows the smaller aperture to control insertion while the larger central portion accommodates and secures the screw head, achieving both easy insertion and secure retention.
3Stability of the object's composition
If the screw head is tightly constrained in the hole, then relative movement between plate and screw is prevented, but the screw cannot be removed when needed for load transfer or stabilizer replacement
Solution Approach 1:
The retention mechanism is designed to be dynamically reversible. During normal operation, the aperture constrains the screw head to prevent movement. When removal is needed, the constraint can be overcome by applying sufficient force to pull the screw head through the aperture, allowing transition from a stable locked state to a removable state.
Solution Approach 2:
The central portion of the hole is designed with sufficient space to accommodate the screw head while maintaining constraint. This pre-designed space provides a buffer that allows the screw to be retained during normal use but can be removed when necessary, preparing the structure for both stable operation and future removal needs.
4Strength
If traditional fixed-angle screw connections are used, then manufacturing and assembly are simple, but effective load transfer from vertebrae to stabilizer cannot be achieved with angled screws
Solution Approach 1:
The hole structure incorporates angular capability by allowing screw placement at various angles within the central portion. This multi-dimensional approach enables effective load transfer for angled screw placements while maintaining a relatively simple single-hole-per-location manufacturing approach, avoiding the need for multiple precisely angled holes.
Data Source
AI summary
A multi-axis connection for transferring load from the vertebrae of a patient to a plate extending from one vertebra to another vertebra when affixed to the respective vertebrae by screws extending through holes in the plate at the level of the respective vertebrae, each screw being oriented at any of a plurality of angles relative to the plate. The threaded shank of each screw is screwed into the vertebral body and the head is positioned in the central portion of the hole, the hole being defined by an aperture, an opening through which the screw extends, and the central portion between aperture and opening. The diameter of the head is larger than the aperture of the hole in the plate and is provided with a screw thread that engages the smaller diameter aperture of the hole to pull the head into the central portion of the hole when the screw is rotated, the head of the screw being retained within the hole by the smaller diameter aperture and the opening of the hole.