Monoplanar Bone Anchoring Device with Frictional Locking
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Solution Overview
Problem
Current bone anchoring devices lack the ability to adjust position effectively in small anatomical spaces, such as cervical vertebrae, and struggle to provide sufficient load resistance and secure locking of angled positions.
Innovation Solution
A bone anchoring device with a receiving part and anchoring element that allows monoplanar adjustment around a single rotational axis transverse to the longitudinal axis, combining features of monoaxial and polyaxial devices for improved stability and ease of handling, featuring a pressure element that limits pivoting to a specific plane and secures the position through frictional forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a monoaxial bone anchoring device is used, then load resistance is improved, but adaptability to anatomical conditions deteriorates
Solution Approach 1:
The bone anchoring device incorporates a pivotable head that can rotate relative to the shaft within a limited angular range, allowing dynamic adjustment of the head's orientation to match anatomical conditions while maintaining the rigid monoaxial structure for load resistance. The pivot mechanism enables the system to adapt between fixed and adjustable states as needed.
Solution Approach 2:
The device allows change in the angular parameter of the head orientation relative to the shaft, limited to a specific range. This parameter change enables adaptation to different anatomical configurations without compromising the overall structural integrity and load-bearing capability of the monoaxial design.
2Adaptability or versatility
If a polyaxial bone anchoring device is used, then adaptability to anatomical conditions is improved, but device complexity increases
Solution Approach 1:
The device is divided into distinct segments: a shaft portion for bone anchoring and a separate head portion for rod reception and positioning. The head can pivot relative to the shaft, creating a segmented structure that provides adjustability while maintaining simpler individual components compared to fully polyaxial designs.
Solution Approach 2:
The head is designed to be pivotable relative to the shaft within a limited angular range, providing dynamic adjustability. This limited polyaxial movement is achieved through a relatively simple pivot mechanism rather than complex multi-axis adjustment systems, balancing adaptability with structural simplicity.
3Ease of operation
If the anchoring element is made pivotable in a limited angular range, then ease of operation is improved, but stability deteriorates
Solution Approach 1:
The head is designed with controlled pivotability within a limited angular range, allowing easy adjustment during surgery. The pivot mechanism is constrained by geometric features such as a spherical head engaging with a receiving part, which provides stable positioning while maintaining ease of operation within the designed angular limits.
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
The device provides enhanced load resistance and secure locking of angled positions, allowing for precise anatomical adjustments in a single plane, improving stability and reducing the need for multiple device types, while enabling interchangeable pressure elements for various clinical applications.
Implementation Method 1
The pressure element (20) is inserted into the receiving part (1) with its second end (22) facing the head (15) and is held loosely by the cooperating crimp bores (26, 27) in a position in which the recess (24) covers at least partly the spherical surfaces (16a, 16b) of the head (15). The pressure element (20) may be secured against rotation in another manner, for example by means of pins or otherwise.
Implementation Method 2
secures the position through frictional forces
Data Source
AI summary
A bone anchoring device includes a receiving part for receiving a rod, the receiving part has a first bore coaxial with a longitudinal axis and a second bore, and an anchoring element having a first end for insertion into the bone and a second end positionable within a second bore, the anchoring element being movable relative to the receiving part in limited angular range about the longitudinal axis, the angles lying in a single plane. The bone anchoring device further includes a fixation element cooperating with the receiving part to lock the anchoring element relative to the receiving part. The anchoring element is pivotable relative to the receiving part around one rotational axis transverse to the longitudinal axis.