Force-Limiting Handle Mechanism for Surgical Instruments
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Solution Overview
Problem
Surgical instruments often cause tissue damage due to excessive force transmission from handle assemblies to end effectors, and can also be damaged by stiff or hard tissues, with issues arising from improper cartridge assembly positioning or malfunction, leading to resistance and instrument damage.
Innovation Solution
A handle assembly with an adjustable force-limiting mechanism that includes a connecting rod, spring, and adjustment screw to control the force applied to the end effector, disengaging the trigger from the drive assembly when a predetermined force is reached to prevent excessive force transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the handle assembly transmits force to the end effector to manipulate tissue, then the surgical instrument can perform cutting or grasping functions, but excessive force may cause damage to tissue
Solution Approach 1:
A force-limiting mechanism is introduced as an intermediary component between the handle assembly and the end effector. This mechanism includes a spring and a disengageable connection that mediates force transmission, allowing controlled force delivery while preventing excessive force from reaching the tissue. The spring acts as a cushioning intermediary that compresses under excessive force, and the disengageable connection allows the mechanism to release and protect tissue when force thresholds are exceeded.
Solution Approach 2:
The force-limiting mechanism changes the force transmission parameter by introducing a variable force characteristic. The spring-based mechanism allows the force transmitted to the end effector to vary based on tissue resistance, automatically adjusting from normal operating force to a limited maximum force. This parameter change enables the system to adapt force delivery to tissue properties, preventing both insufficient and excessive force application.
2Productivity
If the handle assembly applies force to stiff or hard tissues, then cutting or compression functions can be performed, but the surgical instrument itself may be damaged
Solution Approach 1:
The force-limiting mechanism provides beforehand cushioning by incorporating a spring that is pre-loaded to counteract excessive force before it can reach the instrument's critical components. The spring absorbs and cushions the impact of forces generated when cutting or compressing stiff tissues, preventing these forces from damaging the handle assembly or other instrument components. This protective cushioning action occurs automatically during normal operation.
Solution Approach 2:
The force-limiting mechanism serves as a protective intermediary between the handle assembly and the end effector, specifically shielding the instrument from damage. When stiff or hard tissues are encountered, the mechanism's spring and disengageable connection work together to limit the force transmission, preventing the instrument from being damaged while still allowing the surgical function to be performed.
3Ease of manufacture
If the cartridge assembly is devoid of fasteners and the surgeon attempts to continue or reuse the surgical instrument, then resource waste is reduced, but resistance may cause damage to the surgical instrument
Solution Approach 1:
The force-limiting mechanism acts as a protective intermediary that shields the surgical instrument from damage caused by improper cartridge assembly conditions. When a cartridge is devoid of fasteners or improperly positioned, the spring-based mechanism detects the abnormal resistance and limits force transmission, preventing damage to the instrument while still allowing the surgeon to complete the surgical procedure.
Solution Approach 2:
The force-limiting mechanism provides feedback about the cartridge assembly status through the spring's compression characteristics. When the cartridge is improperly positioned or devoid of fasteners, the spring compresses differently than during normal operation, providing tactile feedback to the surgeon about the abnormal condition while simultaneously protecting the instrument from damage.
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
Prevents tissue and instrument damage by limiting the force applied to end effectors, allowing safe manipulation of tissues and reducing the risk of instrument overload, while enabling precise control of the force applied during procedures.
Implementation Method 1
The force-limiting mechanism includes a spring positioned within the actuator and adjacent the second end of the connecting rod
Data Source
AI summary
A safety handle assembly for use with a surgical instrument having an operative distal end portion is disclosed. The handle assembly includes a handle housing and a drive element movably mounted within the handle housing and connected to an associated operative distal end portion. A drive assembly is positioned within the handle housing and is engageable with the drive element to move the drive element within the handle housing. An actuator is movably mounted on the handle housing and an adjustable force-limiting mechanism is interposed between the drive assembly and the actuator. A force-limiting mechanism releasably connects the actuator to the drive assembly. The force-limiting mechanism is adjustable to preset the force at which the actuator separates or breaks away from the drive assembly.