Polyaxial Screw Alignment Instrument for Spinal Surgery
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Solution Overview
Problem
Current spinal fixation systems face challenges in aligning polyaxial screws coaxially, especially after rod or spinal fixation element insertion, leading to reduced surgeon control and increased complexity due to the need for multiple screw types and additional instrumentation.
Innovation Solution
The development of methods and devices that allow for the recording and capture of polyaxial screw orientation before rod capture, using alignment devices like elongate frames with transverse angle indicators or image guidance systems, to ensure coaxial alignment and maintain it throughout the procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyaxial screws are used to facilitate rod capture, then rod capture ability is improved, but surgeon control during corrective forces is reduced
Solution Approach 1:
The receiving member is designed with dynamic movement capability relative to the threaded shank, allowing polyaxial adjustment during rod capture. The set-screw mechanism enables dynamic locking at desired orientations, transforming the system from static to dynamically adjustable, thus maintaining both ease of rod capture and surgeon control.
Solution Approach 2:
The system allows changing the orientation parameter of the receiving member relative to the threaded shank. By adjusting the angular orientation through polyaxial movement and then locking it with the set-screw, the system optimizes both rod capture accessibility and corrective force control at different procedural stages.
2Reliability
If polyaxial screw locking mechanisms are used to lock receiving member to threaded shank, then surgeon control is improved, but alignment precision deteriorates
Solution Approach 1:
The patent replaces traditional mechanical alignment indicators with magnetic field-based alignment technology. Magnetic alignment indicators provide precise coaxial alignment feedback without complex mechanical linkages, enabling accurate alignment while maintaining secure locking control through the set-screw mechanism.
3Manufacturing precision
If multiple screw types (polyaxial, monoaxial, uniplanar) are used to achieve coaxial alignment, then alignment capability is improved, but device complexity increases
Solution Approach 1:
The polyaxial screw design integrates multiple functions into a single device type. The receiving member can accommodate rods at various orientations and be locked in place, combining capabilities previously requiring separate monoaxial, uniplanar, and polyaxial screw types. This universal design reduces instrument complexity while maintaining precise coaxial alignment capability through magnetic indicators and set-screw locking.
4Manufacturing precision
If additional instrumentation is used to ensure coaxial alignment, then alignment precision is improved, but procedure complexity increases
Solution Approach 1:
The magnetic alignment indicators provide self-aligning functionality directly integrated into the polyaxial screw system. The magnetic fields automatically guide the receiving member and threaded shank into coaxial alignment without requiring external alignment instruments or additional procedural steps, thereby simplifying the overall procedure while maintaining high alignment precision.
Data Source
AI summary
Devices and methods for aligning the components of polyaxial screws are described herein. In one embodiment, an alignment instrument includes an elongate frame having a longitudinal axis and a plurality of connection caps slidably disposed along the elongate frame. Each connection cap can removably couple to a polyaxial screw extension tube and selectively lock relative to the elongate frame such that a distance between the plurality of connection caps and an angular orientation of each connection cap relative to the elongate frame is maintained. The instrument can also include a transverse angle indicator to indicate an angular orientation of the elongate frame in a plane transverse to the longitudinal axis of the elongate frame. The device can, for example, capture the orientation of a plurality of polyaxial screws during spinal surgery such that the screws can be returned to the same orientation after manipulation to correct a spinal deformity, etc.