Arthroscopic Jaw Actuation via Screw Conversion Mechanism
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Solution Overview
Problem
Current arthroscopic cutters face limitations in transmitting sufficient closing force to effectively remove hard tissues, such as bone, during surgical procedures like meniscectomy and anterior cruciate ligament reconstruction, due to the limited force transmission in existing motor-driven jaw structures.
Innovation Solution
The design incorporates a conversion mechanism with helical threads that converts rotational motion from a motor drive into longitudinal motion, providing a mechanical advantage by maximizing the number of rotations required to translate the actuator member, thereby increasing the force applied to the jaw structure, which includes a screw mechanism to amplify torque and enhance jaw closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an epicyclic gear mechanism with a tilted cam surface is used to convert rotational motion to axial reciprocation, then rapid actuation of the jaw structure is achieved, but the closing force transmitted to the jaw structure is limited
Solution Approach 1:
The patent replaces the epicyclic gear mechanism with a screw mechanism that converts rotational motion directly to linear motion through threaded engagement. This substitution eliminates the cam surface intermediate step and provides superior mechanical advantage, enabling both rapid actuation and high closing force transmission to the jaw structure
Solution Approach 2:
The screw mechanism enables controlled periodic reciprocating motion of the jaw structure through rotational-to-linear conversion. The threaded engagement provides inherent mechanical advantage during each reciprocation cycle, maintaining high force transmission while achieving rapid actuation through controlled rotation of the actuator member
2Productivity
If the motor drive rotates the shaft at high speed for rapid tissue removal, then productivity increases, but the force available for cutting hard tissue decreases
Solution Approach 1:
The screw mechanism changes the motion parameters by converting high-speed rotation into controlled linear reciprocation with amplified force. The threaded engagement provides mechanical advantage that transforms the motor's rotational speed into high-force linear motion, enabling both rapid actuation and effective cutting of hard tissue
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 enables the arthroscopic device to apply increased mechanical advantage and torque to the jaw structure, allowing for more effective cutting and removal of hard tissues, including bone, while also facilitating rapid and controlled tissue resection with adjustable closing rates.
Implementation Method 1
a first drive element having external helical threads configured to engage inner helical threads formed in the hub
Implementation Method 2
a second drive element having external helical threads that engage internal helical threads formed in the first drive element
Data Source
AI summary
An arthroscopic device is used with a hand piece having a motor drive with a rotating drive shaft. An elongate probe extending along a longitudinal axis and includes a proximal hub on a proximal end. The proximal hub detachably couples to the hand piece, and an operable-closeable jaw structure is disposed on a distal end of the elongate probe. A conversion mechanism carried by the hub converts a rotational motion of the motor drive shaft to a longitudinal motion of an actuator member. The actuator member drives the jaw structure between jaw-open and jaw-closed positions to resect bone and other hard tissues.