Ball-Joint Screw Driver With Rigid Tip Fixation at High Angles
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Solution Overview
Problem
Existing driver devices for spinal surgery, such as those used in anterior lumbar interbody fusion and cervical spine procedures, face challenges in maintaining appropriate force and stability due to the range of angulation in u-joints and wear issues in bushings, making it difficult to securely drive screws into the spinal column.
Innovation Solution
The introduction of a ball-in-socket joint with a spherical head and retention cap, combined with a spring and tapered housing, allows for stable articulation and torque transmission, providing approximately 45-50° of angulation and preventing the driver tip from moving, thus maintaining effective screw driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a u-joint is used to allow the driver head to articulate with respect to an input shaft, then the driver can achieve a range of angulation, but it becomes difficult for the user to maintain appropriate force on the component being driven
Solution Approach 1:
The driver is segmented into distinct functional components: a rigid driver tip assembly, a spring mechanism, and a retention cap system. This segmentation allows the driver tip to maintain rigid force transmission while the spring and retention cap accommodate angular variations, resolving the contradiction between adaptability and ease of operation.
Solution Approach 2:
The spring mechanism provides dynamic compensation for angular deviations. As the driver articulates through different angles, the spring compresses or extends to maintain optimal engagement between the driver tip and the component, ensuring consistent force application across the range of motion.
2Reliability
If a bushing within the driver head is used to retain a driver tip, then the driver tip can be held in place, but the bushing wears out over time causing the driver tip to move around
Solution Approach 1:
The retention cap with its friction-fit engagement provides a simple, replaceable retention mechanism that can be quickly changed when worn. This approach trades the longevity of a permanent bushing for the ease of replacing a simple cap, maintaining reliable driver tip retention throughout the system's service life.
Solution Approach 2:
Instead of retaining the driver tip through a worn bushing, the design inverts the retention approach by using a retention cap that friction-fits onto the driver tip. This reverses the retention direction and eliminates the wear issues associated with traditional bushings, as the cap can be easily removed and replaced without wear degradation.
3Reliability
If a rigid fixation mechanism is used to prevent the driver tip from moving, then torque transmission is improved, but the device complexity increases
Solution Approach 1:
Rigid fixation is applied locally only where needed at the driver tip interface with the component, while the rest of the driver maintains articulation capability through the spring and retention cap mechanism. This localized rigidity provides stable torque transmission without requiring the entire device to be complex and rigid.
Solution Approach 2:
The driver assembly combines different material properties and mechanical characteristics: the rigid driver tip for precise force application, the elastic spring for angular compensation, and the friction-fit retention cap for secure yet replaceable connection. This composite approach achieves reliable torque transmission while keeping the overall mechanism simple and maintainable.
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
This solution enhances the stability and effectiveness of screw insertion by maintaining the driver tip within a useful range of operation, ensuring secure engagement and retention of screws in the spinal column, even during multi-angle screwing operations.
Implementation Method 1
a spring disposed in an end of the input shaft and in a recess of the retention cap
Implementation Method 2
a retention cap having a domed surface to mate with the spherical head
Implementation Method 3
The housing may have a tapered end to positionally retain the spherical head therein
Data Source
AI summary
An articulating driver having a ball-in-socket joint. The driver may include a driver tip having a spherical head, a retention cap having a domed surface to mate with the spherical head, an input shaft, a spring disposed in an end of the input shaft and in a recess of the retention cap opposite that of the domed surface, and a housing that receives the input shaft, the spring, the retention cap and the spherical head. The housing may have a tapered end to positionally retain the spherical head therein. In another aspect, the driver may include a driver tip coupled to the input shaft that includes an interface to engage a screw. A bushing may engage the driver tip at one end and receive the screw at the other end to retain the screw within the driver.