Uniplanar Bone Anchoring Element With Flattened Head And Grooved Receiver
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing uniplanar pedicle screws require high precision in manufacturing and cautious surgical insertion due to the risk of pins losing contact with the screw head, leading to potential pivoting out of the desired plane, especially during derotation maneuvers for scoliotic spines.
Innovation Solution
A uniplanar bone anchoring element with a screw head having flattened sides and a receiving element featuring a tapered through hole and an inner groove with a complementary bearing element, ensuring precise alignment and preventing the bearing element from slipping or rotating, thus maintaining the screw's pivoting within a single plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pins are used to contact the flat surfaces of the screw head, then uniplanar pivoting is achieved, but manufacturing precision requirements increase and reliability decreases due to risk of losing line contact
Solution Approach 1:
A bearing element is introduced as an intermediary component between the screw head and the receiving element. This bearing element has a flattened side that contacts the flattened side of the screw head, ensuring reliable line contact. The bearing element is positioned in a groove of the receiving element, which prevents it from rotating and maintains stable contact throughout the uniplanar pivoting motion, eliminating the risk of losing contact that exists with direct pin-to-screw contact.
2Adaptability or versatility
If pins are used to contact the flat surfaces, then uniplanar pivoting is achieved, but device complexity increases and ease of operation decreases due to risk of pin dislodgment
Solution Approach 1:
The bearing element is pre-positioned in the groove of the receiving element before the screw is inserted. The groove is designed with specific geometry that prevents the bearing element from rotating or dislodging. This preliminary positioning ensures that when the screw is inserted and contacts the bearing element, the uniplanar pivoting motion is immediately constrained without risk of the bearing element falling out or losing contact during surgical insertion.
3Reliability
If high precision manufacturing is used for pins and pin holes, then contact reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The design changes the contact geometry from point contact (pin in hole) to line contact (flattened bearing element surface against flattened screw head surface). This parameter change in the contact interface allows for larger tolerance ranges while maintaining reliable contact. The bearing element's flattened side provides a extended contact surface that is more forgiving of manufacturing variations, reducing the precision requirements compared to pin-and-hole assemblies.
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3
AI summary
The invention relates to a uniplanar bone anchoring element (10) comprising an anchoring screw (12) with a bone thread (14) and a screw head (18), wherein the screw head is flattened on at least one side (17), a receiving element (20) wherein the receiving element has a through-hole that tapers in a lower region (21) and in which the anchoring screw (12) can be received, and two upwardly extending legs (25, 26) with a threaded profile (27) in an upper region designed for screwing on a fastening screw, wherein the receiving element (20) has an internal groove (24) extending at least partially in the circumferential direction in the seating region of the anchoring screw head (18), and a bearing element (40) for insertion into the internal groove (24) of the receiving element (20), wherein the bearing element (40) is partially flattened on at least one side (47).wherein the groove and the bearing element are designed to be complementary such that the bearing element is positioned in the groove in a predetermined position.