Surgical Post Assembly for Rotational Removal in Confined Space
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Solution Overview
Problem
The removal of surgical posts, such as perineal posts, from confined spaces during procedures like fracture repair and hip surgery is challenging due to resistance from patient tissue, making intraoperative removal difficult and inefficient.
Innovation Solution
A surgical assembly with a post and platform design that allows for easy installation and removal by translating a sleeve along the post, enabling the post to be rotated about a laterally extending axis, eliminating the need for longitudinal movement and facilitating countertraction application and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the post is removed by moving it in a direction parallel to its axis (longitudinal translation), then the post can be disengaged from the support, but the movement is resisted by contact with the patient's groin and thigh tissue, making removal difficult
Solution Approach 1:
The patent inverts the traditional removal approach by designing the post with an asymmetric cross-section that allows removal through rotational motion rather than longitudinal translation. The post's geometry enables it to be engaged by moving parallel to its axis but removed by rotating about a lateral axis, effectively reversing the removal mechanism to avoid tissue resistance
Solution Approach 2:
The patent transitions the removal operation from one dimension (longitudinal translation along the post axis) to another dimension (rotation about a lateral axis). By changing the dimension of motion from linear to rotational, the post can be removed without moving through the resistant tissue path, solving the contradiction between ease of removal and tissue resistance
2Ease of manufacture
If the post is designed with a symmetric circular cross-section, then it is easy to manufacture and insert, but it cannot be rotated for removal without also translating longitudinally
Solution Approach 1:
The patent applies asymmetry by designing the post with a non-circular, asymmetric cross-section (such as a D-shape or shape with flat sides). This asymmetric geometry allows the post to be inserted by longitudinal translation while enabling removal through rotation about a lateral axis, as the asymmetric shape prevents simultaneous rotation and translation, thereby solving the removal problem without significantly complicating manufacturing
3Reliability
If the post is securely held by the support structure, then countertraction is effectively applied during surgery, but the post becomes difficult to remove from the confined sterile space
Solution Approach 1:
The patent applies dynamics by designing the post-support interface to have different mechanical characteristics for engagement and disengagement. The asymmetric post geometry creates a dynamic system where the post is securely held during surgery (stable state) but can be easily removed by applying rotational motion (transition to unstable state), allowing the system to switch between stable retention and easy removal based on the applied force direction
Data Source
AI summary
A surgical assembly (20) comprises a post (100) having a longitudinally extending axis (104), a support (56) for resisting movement of the post in a negative longitudinal direction, and a platform (70) offset from the support in a positive longitudinal direction. The platform includes an opening (82) through which the post projects. The opening includes a throat (86). The post has a first dimension which renders the post incapable of passing through the throat and a second dimension which renders the post capable of passing through the throat. Alternate embodiments in which the post can be removably engaged with the support and platform and disengaged therefrom without translating the post in the longitudinal direction are also disclosed.