Programmable Screwdriver Torque Sensor Prevents Bone Screw Stripping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In orthopaedic procedures, it is challenging to determine the appropriate endpoint for screw insertion to avoid over-tightening and screw stripping during fracture plate fixation, as torque is dependent on screw pitch, bone density, and bone-thread interfacial friction, making it difficult for surgeons to achieve optimal fixation without compromising pullout strength.
Innovation Solution
A programmable screw driver equipped with a torque sensor and rotational motion sensor connected to a microprocessor that measures torsional input and rotation, allowing for predetermined torque and rotational limits to be set, alerting the surgeon when to stop tightening to prevent screw stripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If torque limiting method is used for screw insertion, then screw tension and compressive force on fracture reduction are improved, but screw stripping occurs due to inability to control peak torque
Solution Approach 1:
The screw driver incorporates a torque sensor that provides real-time feedback on torque applied during screw insertion. The microprocessor receives torque signals and rotational motion signals, processes this feedback data, and controls the screw driver to prevent exceeding the predetermined torque level, thereby avoiding screw stripping while maintaining optimal compressive force on the fracture reduction.
Solution Approach 2:
The patent replaces the traditional mechanical torque limiting method with an instrumented system using torque sensors, rotational motion sensors, and microprocessor control. This substitution allows precise measurement and control of torque and rotation parameters, enabling the surgeon to achieve optimal fixation without the guesswork inherent in conventional mechanical methods.
2Reliability
If experienced surgeons tighten screws to 86% of maximum torque, then fracture fixation is achieved, but screw stripping still occurs in up to 88% of patients over 50
Solution Approach 1:
The screw driver is pre-programmed with predetermined torque levels and rotational limits based on the specific screw and bone characteristics. Before screw insertion begins, the microprocessor is configured with the appropriate torque threshold, allowing the system to automatically prevent stripping by stopping insertion at the optimal point before harmful effects occur.
Solution Approach 2:
The system dynamically monitors and controls torque and rotation parameters during screw insertion. By changing the operational parameters in real-time based on sensor feedback, the screw driver adapts to variations in bone density, screw pitch, and thread interface friction, preventing screw stripping while maintaining fracture fixation across different patient populations.
3Force
If torque is used as the control parameter for screw insertion, then screw tension is maximized, but the complexity of determining peak torque increases due to multiple variables
Solution Approach 1:
The patent replaces complex mechanical determination of peak torque with an instrumented system using torque sensors, rotational motion sensors, and microprocessor control. This substitution transforms the complex multi-variable problem into a controlled measurement and execution system that automatically handles the complexity.
Solution Approach 2:
The microprocessor acts as an intermediary between the torque sensor and the screw driver motor control. It receives torque signals and rotational motion signals, processes the data according to predetermined parameters, and controls the motor to achieve the optimal torque level, simplifying the overall system architecture while managing the complexity of torque determination.
4Reliability
If the turn-of-the-nut method is used with rotational limit, then screw stripping is prevented, but the surgeon cannot adequately determine when the screw head is seated against the plate
Solution Approach 1:
The screw driver incorporates a rotational motion sensor that provides real-time feedback on the rotation angle of the screw driver shaft. The microprocessor processes this rotational feedback and compares it against predetermined rotational limits, automatically controlling the screw insertion process to ensure the screw head is properly seated against the plate while preventing over-rotation and stripping.
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 screw driver effectively guides surgeons to achieve optimal screw fixation by preventing over-tightening, reducing the risk of screw stripping and maintaining fracture reduction, thereby enhancing the reliability of fracture fixation.
Implementation Method 1
a torque sensor for measuring torsional input during screw insertion
Implementation Method 2
a rotational motion sensor for measuring the rotation of the screw driver
Data Source
AI summary
A programmable screw driver and method for affixing screws into bone is disclosed. The screw driver includes a torque sensor for measuring torsional input during screw insertion, a rotational motion sensor for measuring the rotation of the screw driver, and a microprocessor. Once a surgeon rotates a screw to be affixed to the bone, the torque sensor measures the torque and sends this information to the microprocessor. Once a predetermined torque level is attained, the microprocessor begins to measure subsequent rotation of the screw driver until a predetermined rotational limit, thereby causing a signal to be sent to alert the surgeon to stop tightening.