Lockable Ball-and-Socket Joint for Single-Motion Surgical Retraction
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Solution Overview
Problem
Existing surgical retractor systems face challenges in achieving polyaxial adjustment and locking of tissue retracting implements relative to retractor bodies, requiring complex operations and multiple rotations to achieve sufficient locking strength, which can lead to unintended movement during actuation.
Innovation Solution
A ball-and-socket joint assembly with a compression member and actuator shaft that allows for quick coupling and decoupling, providing provisional locking and sufficient locking strength with minimal movement, utilizing a collet and spring mechanism for frictional retention and adjustable friction levels through cam pin and angled channel interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an expandable element is used to achieve polyaxial adjustment and locking, then the ability to adjust and lock tissue retracting implements is improved, but the operational complexity increases and multiple rotations are required to achieve acceptable locking levels
Solution Approach 1:
The locking mechanism is segmented into distinct functional components: a collet with lobes that can be independently actuated, a cam structure that converts rotational motion to linear compression, and a ratchet mechanism that provides one-way locking. This segmentation allows each component to perform its specific function efficiently, reducing overall operational complexity while maintaining reliable locking.
Solution Approach 2:
The mechanism transitions from a static locked position to a dynamic adjustment phase and back to locked, allowing provisional locking with minimal actuation. The cam structure enables dynamic conversion of rotational input into linear compression of the collet, providing both adjustment capability and secure locking in a single operational sequence rather than requiring multiple rotations.
2Reliability
If a screw mechanism is used to actuate the expandable element, then locking capability is achieved, but multiple rotations are required which can lead to unintended movement during actuation
Solution Approach 1:
The traditional screw mechanism is replaced with a cam-based actuation system. The cam structure converts a single rotational input into linear compression of the collet, eliminating the need for multiple rotations. This substitution maintains the locking capability while significantly improving ease of operation and preventing unintended movement during actuation.
Solution Approach 2:
The mechanism is designed so that the collet is pre-positioned and spring-loaded to engage with the ball connector. The cam structure is pre-configured to translate rotational input into immediate linear compression, achieving locking in a single predetermined motion sequence without requiring multiple adjustments or rotations that could cause unintended movement.
3Ease of operation
If the actuating screw is coupled to the tissue retracting implement, then actuation is achieved, but the implement may move unintentionally during actuation
Solution Approach 1:
The actuation system is segmented so that the cam structure is mounted on the retractor body rather than being coupled to the movable implement. This separation ensures that actuation forces are applied to the stationary body, not the implement, preventing unintended movement while maintaining full actuation capability through the collet's compression action.
Solution Approach 2:
The collet acts as an intermediary between the cam actuation mechanism and the ball connector. The cam compresses the collet, which in turn exerts frictional force on the ball connector to achieve locking. This intermediary arrangement decouples the actuation mechanism from the implement, allowing stable actuation without direct coupling that would cause implement movement.
4Reliability
If friction force is increased to improve locking strength, then resistance to tissue abutting forces is improved, but the friction force may be insufficient when the ball and socket joint is new
Solution Approach 1:
A spring is pre-loaded to exert a preliminary compressive force on the collet, which in turn applies initial friction force to the ball connector. This preliminary action ensures that locking strength is immediately available when the joint is new, eliminating the delay that would otherwise occur while friction force builds up. The spring maintains constant pressure to ensure consistent locking performance throughout operation.
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
Enables easy assembly and disassembly of surgical instruments, providing improved polyaxial restraint and locking with reduced operational complexity and minimal movement requirements, enhancing surgical precision and efficiency.
Implementation Method 1
a spring configured to urge the compression member distally
Implementation Method 2
providing a friction fit between the outer surface of the collet and the lip
Implementation Method 3
rotation and translation of the compression member in the cavity
Data Source
AI summary
A ball and socket joint assembly is disclosed that includes a body defining a cavity, a collet disposed in the cavity to receive a ball of a connector, and an actuator shaft coupled to the collet for rotating and translating the collet in the cavity. The cavity has a distal opening to accept the ball and an engagement feature extending into the cavity. The collet has an outer diameter larger than the opening in the body when the ball is disposed in the collet, and the collet has a corresponding engagement feature around at least a portion of the outer surface for receiving the engagement feature and converting rotation of the compression member into translation of the compression member along a proximal-distal axis of the body. The collet is compressed against the opening of the cavity when the collet is advanced distally against the opening.