Modular Uniplanar Pedicle Screw Assembly
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Solution Overview
Problem
Current pedicle screw assemblies require time-consuming and potentially risky screwing and unscrewing of bone fasteners to switch between polyaxial and uniplanar tulip assemblies during spinal deformity correction procedures, compromising structural integrity and efficiency.
Innovation Solution
A modular pedicle screw assembly that allows a uniplanar tulip assembly to be coupled onto a polyaxial bone fastener using a longitudinal slot and adapter, enabling movement in one plane while preventing movement in other planes, without the need for screwing and unscrewing, through a clamp element and sleeve assembly configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polyaxial pedicle screw assembly is used to allow flexibility in rod placement, then the tulip element can pivot freely in any direction and all planes, but the assembly cannot maintain rigidity in a particular plane during deformity correction
Solution Approach 1:
The system allows dynamic transition between two stable states: polyaxial configuration for flexibility during implantation, and uniplanar configuration for rigidity during deformity correction. The tulip assembly can be converted intra-operatively from a polyaxial design that allows free pivoting to a uniplanar design that constrains movement to maintain rigidity in a specific plane.
Solution Approach 2:
The pedicle screw assembly is divided into separable components: the bone fastener remains fixed in the vertebra, while the tulip assembly can be exchanged or converted. This segmentation allows the surgeon to maintain the bone fastener placement while changing the tulip configuration from polyaxial to uniplanar to achieve the desired rigidity.
2Stability of the object's composition
If a uniplanar pedicle screw assembly is used to maintain rigidity in a particular plane, then the tulip element can pivot in one plane, but switching between polyaxial and uniplanar assemblies requires time-consuming screwing and unscrewing of bone fasteners
Solution Approach 1:
The bone fastener is designed with a universal head geometry that can accommodate both polyaxial and uniplanar tulip assemblies. This multi-functionality allows the same bone fastener to work with different tulip configurations, enabling intra-operative conversion without removing the bone fastener from the vertebra.
Solution Approach 2:
An adapter or conversion mechanism serves as an intermediary between the bone fastener and the tulip assembly. This intermediary component allows the tulip to be converted from polyaxial to uniplanar configuration while remaining attached to the same bone fastener, eliminating the need for time-consuming removal and reinstallation.
3Adaptability or versatility
If the tulip element is uncoupled from the bone fastener to switch assembly types, then different configurations can be used, but the structural integrity of the pedicle/vertebra is compromised
Solution Approach 1:
The bone fastener is pre-installed in the vertebra with a universal head geometry designed to accommodate both polyaxial and uniplanar tulip assemblies. This preliminary action with a versatile bone fastener eliminates the need for subsequent removal and reinstallation, thereby preserving the structural integrity of the pedicle/vertebra while still allowing configuration changes.
4Stability of the object's composition
If a uniplanar tulip assembly is used for deformity correction, then rigidity is maintained in a particular plane, but the assembly requires different bone fastener head geometry and more complex assembly process
Solution Approach 1:
The bone fastener head is designed with universal geometry that simplifies the assembly process by accommodating both polyaxial and uniplanar tulip configurations. This eliminates the need for different bone fastener geometries for different tulip types, reducing device complexity and streamlining the surgical procedure.
Data Source
AI summary
A modular uniplanar pedicle screw assembly for use with a polyaxial bone fastener. The modular assembly comprises a uniplanar tulip assembly adapted to be coupled to a head of the polyaxial bone fastener, wherein the uniplanar tulip assembly includes a longitudinal slot. The modular assembly further includes an adapter having a lower portion and an upper portion. The lower portion is sized and shaped to be received in a recess of the bone fastener head. The upper portion extends from the lower portion and is adapted to slide along the longitudinal slot of the uniplanar tulip assembly to allow movement of the uniplanar tulip assembly in a first plane along a direction that is parallel to a longitudinal axis of the longitudinal slot, the longitudinal slot preventing movement of the uniplanar tulip assembly in a second plane lateral to the first plane relative to the bone fastener.