Stepped Surgical Guide Connection for Alignment Removal
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Solution Overview
Problem
In orthopaedic knee surgery, it is challenging to remove the alignment guide from the cutting guide without disturbing the positioning of the cutting guide, leading to potential inaccuracies in varus-valgus alignment and flexion-extension due to the misalignment between anatomical and mechanical axes.
Innovation Solution
The surgical instrument system incorporates a recess with a stepped surface in the cutting guide and an attachment protrusion with coaxial cylindrical portions of different diameters, allowing for easier disengagement and greater freedom of movement, minimizing the effect of axis misalignment during removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the alignment guide is fixed to the cutting guide using a conventional connection, then the cutting guide is securely positioned on the bone, but the alignment guide becomes difficult to remove without disturbing the cutting guide's positioning
Solution Approach 1:
The connection interface is segmented into two distinct portions: a first portion with a first constant cross-section and a second portion with a second constant cross-section. This segmentation allows the alignment guide to be disassembled from the cutting guide by withdrawing it along the longitudinal axis, enabling easy removal while maintaining secure positioning during surgery.
Solution Approach 2:
The attachment protrusion of the alignment guide is nested within the recess of the cutting guide. The protrusion features a first cylindrical portion and a second cylindrical portion with different cross-sections that fit into corresponding portions of the recess, creating a nested structure that provides stable positioning but allows straightforward extraction along the longitudinal axis.
2Ease of operation
If the alignment guide and rod are withdrawn along the anatomical axis, then they can be removed from the bone, but the misalignment with the mechanical axis causes undesired forces on the cutting guide
Solution Approach 1:
The connection between the alignment guide and cutting guide is designed to be dynamic rather than rigid. The stepped cylindrical portions allow for controlled movement and adjustment during withdrawal, accommodating the 7-degree angle difference between anatomical and mechanical axes while minimizing harmful forces on the cutting guide positioning.
3Device complexity
If a conventional connection between alignment guide and cutting guide is used, then the structure is simple, but the disengagement requires a long withdrawal distance that increases misalignment effects
Solution Approach 1:
The connection interface is divided into two distinct cylindrical portions with different cross-sections. This segmentation enables disengagement to occur over a much shorter withdrawal distance compared to conventional single-portion connections, thereby reducing the cumulative effect of misalignment between anatomical and mechanical axes during removal.
Data Source
AI summary
A surgical cutting guide (8) is described which comprises a body section delimiting a recess (14) extending into the body section from an external surface. The recess has a central axis and is for receiving an attachment protrusion (18) from a surgical alignment guide (6). The recess comprises: a first portion (36) having a first constant cross section along the central axis; and a second portion (38) having a second constant cross section along the central axis which is larger than the first constant cross section. The first and second portions are coaxial with the central axis and the second portion is closer to the external surface than the first portion. This configuration creates a stepped surface in the recess which is engaged by corresponding features on a protrusion of a surgical alignment guide. The attachment protrusion (18) of the alignment guide (6) has a central axis and comprises: a first portion (20) having a first constant cross section along the central axis; and a second portion (22) having a second constant cross section along the central axis that is larger than the first constant cross section. The first portion is further away than the second portion, and the first and second portions are coaxial with the central axis. The surgical cutting guide and surgical alignment guide form a system in which the alignment guide can be removed more easily from the cutting guide because there is more freedom of movement once the stepped surfaces are disengaged.