Internal Fixation Member Set with Dynamic Rotation Control
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Solution Overview
Problem
Existing internal fixation systems for bones, particularly in orthopedic applications, face challenges in securely anchoring and stabilizing components without easy separation, which can lead to instability and complications during surgical procedures and post-operative recovery.
Innovation Solution
The internal fixation member set includes a screw assembly with a tubular outer member and an inner member, where the inner member is movable between positions to restrict the rotation range of the screw head, preventing it from falling off and ensuring secure anchoring in the bone, utilizing a combination of spherical and cylindrical surfaces for precise alignment and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the head is freely rotatable in the outer member, then ease of operation is improved, but reliability deteriorates due to risk of falling off
Solution Approach 1:
The inner member is designed to be movable between a first position during insertion and a second position for retention. During insertion, the inner member is at the first position allowing free rotation. After insertion, the inner member moves to the second position to restrict rotation and prevent falling off. This dynamic transition resolves the contradiction between ease of operation and reliability.
Solution Approach 2:
The retention mechanism is divided into two functional segments: the outer member that provides structural housing and rotation, and the inner member that provides adjustable retention. This segmentation allows the outer member to maintain ease of operation while the inner member ensures reliability by preventing accidental disassembly.
2Reliability
If the inner member is fixed in position, then reliability is improved, but ease of operation deteriorates due to difficult insertion
Solution Approach 1:
The inner member transitions from a movable state during insertion to a fixed state during retention. The movable state allows easy insertion and extraction for assembly/disassembly operations. The fixed state provides reliable retention security. This dynamic behavior resolves the contradiction between reliability and ease of operation.
Solution Approach 2:
The interference part on the inner member is preliminarily positioned away from the head during insertion to allow easy assembly. After insertion is complete, the inner member moves to engage the interference part with the head, establishing preliminary retention. This preliminary action sequence resolves the contradiction by allowing easy insertion first, then securing retention.
3Reliability
If the rotation range is restricted, then reliability is improved, but adaptability deteriorates due to limited adjustment
Solution Approach 1:
The rotation restriction is dynamically applied: during the insertion phase, the head can rotate freely within a large range to accommodate various insertion angles and achieve proper positioning. After insertion, the inner member engages to restrict rotation, providing stability. This temporal separation of freedom and restriction resolves the contradiction between reliability and adaptability.
Solution Approach 2:
The system allows preliminary free rotation to achieve proper positioning and alignment during insertion. Once positioned, the retention mechanism engages to lock the position. This preliminary action of free movement followed by restriction resolves the contradiction by allowing adaptability during insertion while ensuring stability during retention.
Data Source
AI summary
An internal fixation member set includes an internal fixation member, an inner member, and an outer member. The outer member has a first opening and a second opening, and rotatably retains a head of the inner fixation member. The inner member is inside the outer member and movable between a first position farther from the head and a second position nearer the second opening than the first position. The head has a first rotation range with the inner member at the first position and a second rotation range with the inner member at the second position. The second rotation range is smaller than the first rotation range with an interference between interference parts. A reference rotational position at which the head is insertable into or extractable from the outer member is included in the first rotation range and is not included in the second rotation range.