Taper-Locking Fixation for Orthopedic Rods
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current orthopedic fixation methods lack the necessary adjustability and ease of use for securing off-axis members within other devices, particularly in spinal applications, where precise positioning and orientation are critical for alleviating various spinal disorders.
Innovation Solution
A self-locking taper mechanism that secures a cylindrical rod within a receiving member, allowing polyaxial motion before locking out, utilizing a tapered wedge and spherical collet within an implant member, enabling adjustable and secure fixation in orthopedic procedures such as spinal fixation and facet joint replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed-axis fixation method is used, then the device structure is simple, but the adjustability for positioning and orientation is limited
Solution Approach 1:
The fixation device transitions from a fixed-axis design to a dynamic polyaxial system where the rod can be positioned at multiple angles relative to the screw body. The spherical collet and tapered wedge mechanism enable the rod to rotate and adjust to different orientations before being locked in place, providing adaptability without excessive complexity.
Solution Approach 2:
The fixation device is divided into separate functional components: a screw body, a spherical collet, and a tapered wedge. This segmentation allows each component to perform its specific function independently - the screw provides anchorage, the collet provides polyaxial adjustment, and the wedge provides locking - thereby achieving versatility while managing complexity through modular design.
2Adaptability or versatility
If a polyaxial adjustment mechanism is added, then the positioning and orientation flexibility is improved, but the device complexity increases
Solution Approach 1:
The polyaxial adjustment mechanism is nested within the screw body structure. The spherical collet is positioned inside the screw head, and the tapered wedge is nested within the collet. This nested arrangement allows the polyaxial functionality to be integrated into the existing fixation device without requiring separate external adjustment mechanisms, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The tapered wedge mechanism provides self-locking functionality where the act of inserting or tightening the wedge automatically locks the rod in its desired position without requiring additional locking steps or complex fastening mechanisms. The geometry of the tapered surfaces creates self-contained locking action that simplifies the overall mechanism.
3Reliability
If a secure locking mechanism is implemented, then the fixation reliability is improved, but the ease of operation is reduced
Solution Approach 1:
The complex multi-step locking mechanism is replaced with a simplified tapered wedge system that uses basic mechanical principles of friction and geometry. The tapered surfaces convert axial force into radial clamping force, providing secure locking through a single intuitive motion rather than requiring multiple adjustment steps or complex fastening procedures.
Solution Approach 2:
The locking mechanism is designed to be self-actuating through the tapered geometry. As the wedge is inserted or tightened, it automatically generates the clamping force needed to secure the rod without requiring additional locking actions. The system serves itself by converting the insertion motion directly into the locking action, improving ease of operation while maintaining reliability.
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 solution provides high adjustability and ease of use, ensuring secure fixation while allowing for precise positioning and orientation of orthopedic implants, effectively addressing the challenges of existing methods by enabling polyaxial rotation and lock-out, thus improving the treatment of spinal disorders.
Implementation Method 1
A self-locking taper mechanism that secures a cylindrical rod within a receiving member
Implementation Method 2
utilizing a tapered wedge and spherical collet within an implant member
Data Source
AI summary
A fixation system is designed to lock an elongated member within a housing member, permitting positional and/or orientational adjustment of the elongated member prior to locking. The system includes a housing member, a slotted spherical collet, an elongated member, and may include a tapered wedge, which may be a discrete component or formed as part of the elongated member. The housing member and/or elongated member may be implantable. The elongated member may be positioned in the wedge, the wedge in the collet, and the collet in the housing such that when compression force is applied to the wedge and the collet, the wedge contracts about the elongated member and the collet expands to engage the housing, thus locking the elongated member relative to the housing. The collet may have a tapered channel with a degree of taper equal to the tapered wedge. The collet may have multiple slots to allow uniform radial expansion and compression.