Convertible Spinal Screw Polyaxial to Monoaxial Conversion
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Solution Overview
Problem
Existing spinal fixation systems face challenges in achieving secure and stable connections while allowing for adjustable movement of fastener elements during surgical procedures, as preselected components may not always provide the ideal degree of stability or flexibility.
Innovation Solution
A spinal fixation system comprising a screw, a body, and a pressure cap that allows for polyaxial movement initially and can be converted to monoaxial movement through a mating mechanism, using a pressure cap to restrict the screw's movement, enabling on-the-spot adjustments during surgery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a screw is designed to allow polyaxial movement for optimal alignment during surgery, then the ease of operation and adaptability improve, but the stability and reliability of the fixation connection deteriorate
Solution Approach 1:
The screw system transitions from a static fixed-angle design to a dynamic convertible design that can change its degree of freedom during surgery. The screw initially allows polyaxial movement for alignment, then can be converted to monoaxial movement for stability, making the system adaptable to different surgical phases
Solution Approach 2:
The system changes the movement parameters of the screw by converting from polyaxial to monoaxial configuration. This parameter change is achieved through a conversion mechanism that alters the geometric constraints of the screw, transforming its degrees of freedom to match different surgical requirements
2Device complexity
If preselected components are used for spinal fixation, then the device complexity is reduced, but the adaptability to adjust movement degree during surgery deteriorates
Solution Approach 1:
The screw is designed with multi-functionality, serving both as a polyaxial screw for alignment and as a monoaxial screw for stable fixation. This universal design eliminates the need to preselect between different screw types, as one screw can perform both functions through conversion
3Reliability
If a screw is converted from polyaxial to monoaxial movement during surgery, then the stability and reliability improve, but the ease of operation and alignment flexibility deteriorate
Solution Approach 1:
The screw is initially configured in polyaxial mode before surgery or at the beginning of the procedure, allowing easy alignment and positioning. The conversion to monoaxial mode occurs after alignment is achieved, ensuring that alignment flexibility is maintained when needed while stability is enhanced when required
Data Source
AI summary
Disclosed herein are spinal fixation systems that may comprise a screw, a body, and a pressure cap. A screw may comprise a head at a proximal end, a bone connection element at a distal end, and a first mating element disposed on a head of a pedicle screw. A body may comprise a proximal end, a distal end, a mounting rod receiving channel at a proximal end, and a screw head receiving aperture at a distal end. A portion of the mounting rod receiving channel may be operable to receive a compression element. A pressure cap may comprise a proximal end, distal end, and a second mating element on a distal end. A first mating element of the screw may be configured to mate with the second mating element of the pressure cap thereby limiting the pivotal movement of the screw to that of a monoaxial screw.