Bone Fastener Instrument Worm Gear Assembly
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Solution Overview
Problem
Current interspinous stabilization systems for spinal disorders lack a secure and rigid attachment mechanism to prevent device migration and promote vertebral fusion, especially in minimally invasive surgeries, where traditional tools are cumbersome and time-consuming.
Innovation Solution
A bone fastener assembly instrument with a slim profile, featuring a pair of handles, a spring bias mechanism, and a transmission mechanism with worm gears, allowing for precise alignment and quick assembly of a threaded bolt and nut to securely attach an implantable device to the spinous process, while maintaining a low profile for ease of use in MIS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bone fastener assembly tools are used, then the attachment security is improved, but the device profile becomes cumbersome and assembly time increases
Solution Approach 1:
The bone fastener assembly instrument features a nested structure where the nut is received within the hollow cylindrical body of the instrument. The threaded bolt passes through the instrument with the nut positioned inside, allowing compact storage and handling while maintaining proper alignment for assembly. This nesting approach reduces the overall tool profile without compromising the secure attachment capability.
Solution Approach 2:
The instrument is divided into distinct functional segments: a hollow cylindrical body for holding the nut, a transmission mechanism with worm gears for controlled rotation, and a handle assembly for operator control. This segmentation allows each component to be optimized independently while maintaining a compact overall structure suitable for minimally invasive procedures.
2Reliability
If traditional assembly methods are used, then secure attachment is achieved, but assembly time becomes excessive
Solution Approach 1:
The nut is pre-positioned within the instrument's hollow body before the bolt is inserted. The instrument is pre-loaded with the nut in the correct orientation, and the transmission mechanism is pre-configured to engage the bolt threads immediately upon insertion. This preliminary preparation eliminates time-consuming alignment steps during the actual assembly process.
Solution Approach 2:
The manual threading operation is replaced with a controlled transmission mechanism using worm gears. This mechanical system provides precise rotational control and self-locking capability, ensuring secure attachment while reducing the number of manual rotations required compared to traditional hand-threading methods.
3Ease of operation
If a slim profile instrument is used, then ease of use in MIS is improved, but alignment precision may be compromised
Solution Approach 1:
The instrument serves as an intermediary device that maintains precise alignment between the bolt and nut during assembly. The hollow cylindrical body acts as a guide that constrains the bolt's path and ensures the nut remains properly positioned. This intermediary structure provides alignment precision while keeping the overall instrument profile slim for minimally invasive access.
Solution Approach 2:
The instrument's geometry and the interaction between the bolt and nut create self-aligning features. The threaded engagement and the constrained movement within the hollow body automatically guide the components into proper alignment without requiring complex external alignment tools or procedures.
4Reliability
If rigid attachment mechanism is implemented, then device migration is prevented, but assembly complexity increases
Solution Approach 1:
The complex multi-step rigid attachment process is replaced with a simplified worm gear transmission system. The worm gear mechanism provides controlled rotational movement that threads the bolt into the nut, creating a rigid attachment. The self-locking nature of the worm gear ensures the attachment remains secure without requiring additional locking mechanisms or complex assembly procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates secure attachment of interspinous stabilization devices with reduced assembly time and improved stability, enabling precise alignment and quick threading of components, thus enhancing vertebral fusion and preventing device migration during spinal stabilization procedures.
Implementation Method 1
The instrument may also include a spring bias mechanism between the handles.
Implementation Method 2
This transmission mechanism may comprise a drive shaft that operates through rotation of a series of worm gears or gear wheels.
Data Source
AI summary
A bone fastener assembly instrument that can assemble a two-component bone fastener during surgery is provided. The bone fastener may be of a type that comprises a threaded bolt and nut for securing an implantable device to bone, such as a spinous process. A method for using the bone fastener assembly instrument is also provided.