Rod-to-Bone Anchor Coupling With Angled Cam Locking
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Solution Overview
Problem
Existing polyaxial bone anchoring devices require complex and time-consuming adjustments for locking and unlocking the bone anchor and rod during spinal column correction procedures.
Innovation Solution
A coupling device with a pressure member and actuating portion that allows for a rotational movement to be transformed into a linear movement, enabling quick and easy locking and unlocking of the bone anchor, using a cam mechanism and instrument-assisted actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polyaxial bone anchoring device is used to correct multiple segments of the spinal column, then the ability to adjust bone anchor and rod positions is improved, but the time and complexity of repeated locking and unlocking adjustments increases
Solution Approach 1:
The locking mechanism is designed to be dynamically controllable through the actuating portion, allowing the pressure member to be moved between locked and unlocked states. The actuating portion can be rotated to selectively engage or disengage the pressure member from the bone anchor head, enabling quick transitions between locked and unlocked positions without complex manual manipulation.
Solution Approach 2:
The manual manipulation mechanism is replaced with an actuating portion that can be operated by a surgical instrument. The actuating portion includes engagement features that interface with the pressure member, allowing the instrument to automatically move the pressure member between locked and unlocked positions, reducing the time and complexity of repeated adjustments.
2Reliability
If a locking mechanism is designed to securely clamp the bone anchor head, then the reliability of the connection is improved, but the ease of operation for locking and unlocking is worsened
Solution Approach 1:
The actuating portion serves as an intermediary between the surgical instrument and the pressure member. It includes engagement features such as teeth or cam surfaces that interface with corresponding features on the pressure member, allowing the instrument to easily move the pressure member between locked and unlocked positions while maintaining secure clamping when locked.
Solution Approach 2:
The locking mechanism uses a dynamic pressure member that can be selectively positioned. When the actuating portion is rotated into the engaged position, the pressure member is moved to apply clamping force on the bone anchor head. When rotated to the disengaged position, the pressure member retracts, allowing easy unlocking without compromising the security of the clamped position.
3Ease of operation
If the actuating portion rotates around an axis perpendicular to the central axis to move the pressure member, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
The actuating portion serves multiple functions: it acts as a lever for the surgical instrument to apply force, provides engagement features (such as teeth or cam surfaces) to interface with the pressure member, and defines the rotational axis for the transformation of rotational to linear movement. This multi-functionality reduces the need for additional separate components, thereby reducing overall device complexity while improving ease of operation.
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 repeated, simple, and efficient adjustments of the bone anchor and rod position, allowing for easier surgical correction steps without obstructing the rod channel during temporary locking.
Implementation Method 1
the actuating portion comprises a cam portion and the pressure member follows the movement of the cam portion
Implementation Method 2
exert pressure on an inserted head to move the inserted head from a non-locking position in which an inserted head is pivotable in the receiving part to a locking position in which the head is clamped
Data Source
Figure 1~2
Figure 3~6
Figure 7~10
AI summary
A coupling device for coupling a rod to a bone anchor, the coupling device comprising a receiving part (5) configured to receive a head (3) of the bone anchor (1), the receiving part (5) having a first end (5a) and a second end (5b), a central axis (C) extending through the first end (5a) and the second end (5b), and two legs (54) defining a recess (53) at the first end for receiving the rod; and a pressure member (6) arranged in the receiving part (5) to exert pressure on an inserted head (3), an actuating portion (7) configured to act on the pressure member (6), wherein the actuating portion (7) is configured to rotate at least partially around an axis of rotation (R) that extends at an angle relative to the central axis (C) to move the pressure member (6) from a non-locking position in which an inserted head (3) is pivotable in the receiving part (5) to a locking position in which the head (3) is clamped.