Bone Rod Coupling with Independent Polyaxial Head Locking
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Solution Overview
Problem
Conventional coupling devices for polyaxial bone anchoring devices lack an easily accessible and operable locking mechanism for the head, making adjustments during surgery cumbersome and requiring additional fixation members like set screws.
Innovation Solution
A coupling device with a receiving part, pressure member, and locking member that allows provisional locking of the head independently from the rod, enabling easy angle and position adjustments without a set screw, and can be accessed from various angles (bottom, side, or top) for enhanced surgical flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional coupling device uses a set screw or fixation member to lock the head, then the head can be locked securely, but the locking mechanism becomes difficult to access and operate during surgery
Solution Approach 1:
The locking function is extracted from the rod-fixation system and assigned to a dedicated locking member that operates independently. The locking member can be actuated from outside the coupling device through the rod channel, separating the locking action from the rod insertion and fixation process.
Solution Approach 2:
The locking member acts as an intermediary element that transmits the locking action from the external operator to the head. It engages the head directly and can be actuated through the rod channel, serving as a mediator between the external tool and the internal head component.
2Stability of the object's composition
If additional fixation members like set screws are used to secure the rod, then the rod position can be fixed, but the device complexity increases and surgical steps become more cumbersome
Solution Approach 1:
The rod channel serves multiple functions: it guides the rod into position, allows actuation of the locking member, and provides structural support. This multi-functionality eliminates the need for separate fixation members, as the rod channel itself contributes to both positioning and securing the rod.
Solution Approach 2:
The functions of rod guidance, rod positioning, and head locking are merged into a single integrated structure. The rod channel and locking member work together as a combined system, eliminating the need for separate set screws or fixation members that would otherwise be required.
3Adaptability or versatility
If the head locking requires rod placement first, then the rod can be secured, but the head cannot be locked independently and correction steps become limited
Solution Approach 1:
The head can be locked in the desired angular position before the rod is fully secured or before final fixation. The locking member allows preliminary locking of the head at any angle within the rod channel, enabling surgeons to set the correct orientation before committing to final fixation.
Solution Approach 2:
The system allows dynamic adjustment of the head angle during surgery. The head can be rotated within the rod channel to achieve the desired polyaxial orientation, and the locking member can be actuated at any point during this adjustment process to secure the final position, providing dynamic flexibility rather than fixed pre-determined angles.
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 multiple adjustments during surgery by allowing easy and independent locking of the head relative to the rod, reducing the need for additional fixation members and improving surgical efficiency.
Implementation Method 1
a pressure member positionable in the receiving part such that the pressure member extends at least partially into the accommodation space for exerting pressure onto an inserted head
Implementation Method 2
the locking member is configured to exert pressure onto the head only from one side in a direction different from the axial direction
Data Source
AI summary
A bone anchoring device for coupling a rod to a bone includes a bone anchoring element with a head and a shank, a receiving part having an accommodation space for pivotably holding the head of the bone anchoring element, and a recess for receiving the rod, a pressure member for exerting pressure on the head in the receiving part, and a separate locking member movable relative to the receiving part from a first position where the head of the bone anchoring element is insertable into the accommodation space, to a second position where the locking member directly engages and exerts pressure on the head to hold a position of the head relative to the receiving part.