Threshold-Torque Screw Module for Stable Fusion Cage Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional screw driving structures for implants that require expansion in the body lack a mechanism to prevent screw loosening due to external impacts or fatigue, leading to instability of the expanded implant state.
Innovation Solution
A screw driving module with a threshold torque setting mechanism that prevents screw rotation below a set torque threshold, ensuring stable expansion by allowing rotation only when torque greater than or equal to the threshold is applied, using a screw head with grooves and a threshold torque setting member to secure the screw in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional screw driving structure without a separate preventing configuration is used, then the device complexity is reduced, but the reliability of maintaining the expanded state deteriorates due to screw loosening under impact or fatigue
Solution Approach 1:
The threshold torque setting member is disposed inside the housing and engages with the screw head when the screw is inserted. The preventing configuration is nested within the existing screw driving structure, allowing the housing to serve dual functions: accommodating the screw during rotation and containing the threshold torque setting member that prevents loosening. This nested arrangement adds reliability without significantly increasing overall device complexity.
Solution Approach 2:
The threshold torque setting member acts as an intermediary between the screw head and the housing. It engages with the screw head through the first grooves and transmits the threshold torque requirement, while also interacting with the housing structure. This intermediary component mediates the force transmission and provides the preventing function without requiring a completely separate complex system.
2Reliability
If a threshold torque setting member is added to prevent screw loosening, then the reliability of maintaining the expanded state is improved, but the device complexity increases
Solution Approach 1:
The housing serves multiple functions: it accommodates the screw head during rotation, contains the threshold torque setting member, and provides structural support. The threshold torque setting member itself performs dual functions by engaging with the screw head through grooves and interacting with the housing. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while improving reliability.
Solution Approach 2:
The preventing configuration is merged with the existing screw driving structure. The threshold torque setting member is integrated into the housing, and its engagement mechanism with the screw head is combined with the screw's rotational path. This merging approach consolidates multiple functions into existing components rather than adding entirely separate systems, thus improving reliability with minimal increase in component count.
3Reliability
If the threshold torque setting member engages with the screw head through grooves, then the mechanical threshold torque is effectively applied, but the manufacturing precision requirements increase
Solution Approach 1:
The grooves are formed locally on specific portions of the screw head rather than requiring precision across the entire component. The threshold torque setting member engages with these localized groove features, concentrating the precision requirements to specific areas. This local quality approach allows the majority of the screw and housing to be manufactured with standard tolerances while achieving reliable threshold torque application at the engagement points.
Solution Approach 2:
The grooves are pre-formed on the screw head during manufacturing, establishing the engagement geometry before assembly. The threshold torque setting member is designed to match these pre-formed grooves, allowing for tolerance accumulation to be managed during the screw manufacturing process rather than during final assembly. This preliminary action approach reduces the stringency of precision requirements during the assembly operation.
Data Source
AI summary
A screw driving module and an intervertebral fusion cage including same are disclosed. The screw driving module according to an embodiment of the present invention may comprise: a screw including a screw head and a screw body extending from the screw head and having a screw thread on an outer circumferential surface thereof; a housing in which the screw head is rotatably accommodated; and a threshold torque setting member disposed in the housing and configured to prevent rotation of the screw head when torque is less than a threshold torque set on the screw head and permit rotation of the screw head when torque equal to or greater than the threshold torque is applied.