Ultrasonic Sonotrode Cap Geometry for Stable Tissue Ablation
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Solution Overview
Problem
Existing ultrasonic surgical instruments face challenges with sonotrodes that are susceptible to deformations and lateral deflections, limited controllability, and inefficient debris removal, particularly when treating hard and soft tissues under varying spatial conditions.
Innovation Solution
A sonotrode design with a cap having a concave surface and a center of mass on the longitudinal axis, featuring sharp rims and a convex surface to enhance axial vibration stability, improve debris transport, and allow for controlled tissue ablation in multiple directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a blade-like sonotrode is used for cutting bone tissue, then cutting capability through dense cortical bone is improved, but susceptibility to deformations and lateral deflection increases
Solution Approach 1:
The sonotrode is divided into functionally distinct segments: a blade-like cutting portion for penetrating cortical bone and a cranked head portion for shaping and rasping. This segmentation allows each part to be optimized for its specific function while reducing overall deformation susceptibility through the cranked configuration that distributes mechanical stresses.
Solution Approach 2:
The sonotrode incorporates a cranked configuration that introduces a lateral dimension to the cutting approach. The cranked head portion extends radially outward from the longitudinal axis, enabling the instrument to approach bone surfaces from multiple angles and reduce reliance on a single blade orientation, thereby decreasing lateral deflection effects.
2Shape
If a cranked sonotrode head is used for shaping bone surface, then well-defined contact surface is provided, but restriction and controllability of treatment location is reduced
Solution Approach 1:
The sonotrode features localized functional zones: the cranked head portion provides a well-defined contact surface for shaping, while the blade-like portion offers controlled cutting capability. The distal end includes specifically positioned ablative structures (spikes or edges) that are evenly distributed, allowing precise treatment of specific bone regions while maintaining controllability through localized action rather than diffuse contact.
3Productivity
If ablative structures are evenly distributed around the full distal end, then ablation capability is improved, but restriction and controllability of treatment location is reduced
Solution Approach 1:
Rather than uniform distribution, the sonotrode employs non-uniform distribution of ablative structures at the distal end. The structures (spikes or edges) are strategically positioned to address specific treatment requirements, with varying density and positioning optimized for different bone regions and surgical applications, thereby maintaining controllability while preserving ablation effectiveness.
4Strength
If a blade-like sonotrode is used for cutting, then cutting through dense cortical bone is achieved, but susceptibility to lateral deflection increases
Solution Approach 1:
The sonotrode separates cutting and shaping functions into distinct segments. The blade-like portion handles cutting through dense cortical bone with optimized geometry for penetration, while the cranked head portion handles shaping and rasping. This functional segmentation reduces lateral deflection by preventing the blade from bearing unnecessary lateral loads during shaping operations.
Solution Approach 2:
The sonotrode is constructed from composite or multi-material structures that combine materials with different mechanical properties. The blade portion uses materials optimized for cutting strength and edge retention, while the cranked head uses materials with higher flexibility and shock absorption, reducing lateral deflection during varied surgical maneuvers.
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
The design stabilizes axial vibrations, enhances debris removal, and improves controllability and efficiency in ablating both hard and soft tissues, suitable for both open and minimally invasive surgeries.
Implementation Method 1
A sonotrode (1) for an ultrasonic surgical instrument for carrying out an ablative process, such as cutting, rasping, scraping and/or reaming, on tissue (10) by use of mechanical oscillations
Implementation Method 2
A sonotrode design with a cap having a concave surface and a center of mass on the longitudinal axis, featuring sharp rims and a convex surface to enhance axial vibration stability
Implementation Method 3
enhances debris removal
Data Source
AI summary
A sonotrode includes a stem extending along a longitudinal axis and a cap configured to carry out an ablative process on tissue using mechanical oscillation. The cap has at least one portion that protrudes further in a radial direction than the stem, and the at least one portion has at least one sharp rim. A surface of the cap, which is arranged between a distal end of the stem and the sharp rim of the portion, is a concave surface and/or runs at an opening angle with respect to the stem that is equal or smaller than 90 degrees. A center of mass of the cap is on the longitudinal axis.