Intramedullary Nail Locking Mechanism Prevents Medial Migration
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Solution Overview
Problem
Current internal fixation devices for long bone fractures, such as those in the femur, face challenges in preventing medial migration of implants, which can lead to complications like protrusion into the acetabulum, while allowing for necessary lateral movement.
Innovation Solution
An intramedullary device with an oblique opening and a locking mechanism that includes a channel and a pawl system, allowing for lateral movement of the implant while preventing medial migration through angled abutting structures and a biasing member that engages the pawl with the implant's abutting surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the implant is allowed to move laterally relative to the intramedullary nail, then the implant can accommodate bone healing movements, but the implant may migrate medially through the intramedullary device causing complications
Solution Approach 1:
The locking mechanism is segmented into multiple independent components: a pawl element with engagement features, an actuator element, and a spring element. This segmentation allows each component to perform its specific function while working together to achieve both lateral movement permission and medial migration prevention through distributed mechanical interactions
Solution Approach 2:
The pawl element acts as an intermediary between the implant and the intramedullary nail. It selectively engages with the implant's lateral movement surface to permit controlled lateral displacement while blocking medial migration through its ratchet-like engagement geometry, thus mediating the contradictory requirements of movement freedom and position control
2Reliability
If a locking mechanism is added to prevent medial migration, then implant stability is improved, but the device complexity increases
Solution Approach 1:
The locking mechanism employs dynamic elements including a spring-loaded pawl that can automatically engage and disengage based on implant movement direction. The pawl rotates about a pivot point, dynamically adapting its engagement state: it locks during medial migration attempts while allowing lateral movement, providing intelligent position-dependent control without complex actuators
Solution Approach 2:
The spring element provides self-service by automatically biasing the pawl into the engaged position with the implant. The mechanism uses the implant's own movement forces to trigger pawl engagement or disengagement, eliminating the need for external power sources or complex control systems while maintaining reliable locking functionality
Data Source
AI summary
A device for treating fractures, comprises an intramedullary member sized and shaped for insertion along a longitudinal axis of a bone within a medullary canal thereof, the intramedullary member including an opening extending obliquely therethrough, the opening, when the intramedullary member is in a desired position within a bone, aligning with a desired axis along which an implant is to be inserted into a bone, the intramedullary member including a channel formed therewithin and opening to the opening and a locking mechanism mounted in the channel, the locking mechanism including a locking abutting structure extending into the opening in combination with an implant sized to be slidably received through the opening and inserted along the desired axis, the implant including a plurality of implant abutting structures aligned to engage the locking abutting structure preventing medial movement of the implant relative to the intramedullary member.