Guided Helical Osteotome Blade for Bone-Preserving Humeral Stem Removal
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Solution Overview
Problem
Explanting a well-fixed anatomical humeral stem with a porous proximal section and a smooth distal section during revision shoulder arthroplasty poses a significant challenge due to the difficulty in preserving bone stock and the risk of structural defects leading to bone fractures.
Innovation Solution
A guided helical osteotome blade system that includes a cannulated blade chuck, a blade guide, and a guide rod, allowing the osteotome blade to follow a helical path along the humeral stem, minimizing bone loss by cutting under the collar and fin without creating a window in the cortical wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional methods are used to explant a well-fixed humeral stem, then the stem can be removed, but significant bone loss occurs and structural defects leading to fractures may occur
Solution Approach 1:
The explantation process is segmented into multiple controlled cutting passes using a sequential oscillating saw system. The blade makes multiple incremental cuts rather than attempting to remove the stem in one action, allowing gradual separation that preserves bone stock while ensuring complete stem removal. Each cut segment is controlled to minimize bone loss.
Solution Approach 2:
A guide rod acts as an intermediary element that is first inserted into the medullary canal and then used to guide the oscillating saw blade. This intermediary ensures precise trajectory control of the cutting blade, preventing deviation that could cause bone fractures while enabling controlled removal of the humeral stem.
2Productivity
If aggressive cutting methods are used to remove the stem, then the stem can be fully removed, but the cortical wall may be compromised leading to fractures
Solution Approach 1:
The system employs an oscillating saw blade that dynamically moves back and forth in a controlled oscillation pattern rather than a static cutting action. This dynamic cutting approach allows the blade to progressively separate bone and cement interfaces through repeated micro-cuts, efficiently removing the stem while minimizing the risk of catastrophic bone fracture.
Solution Approach 2:
The guide rod is inserted into the medullary canal before the cutting process begins. This preliminary action establishes a safe trajectory path that prevents the cutting blade from deviating and compromising the cortical wall. The pre-positioned guide rod acts as a mechanical constraint that protects against harmful cutting deviations.
3Manufacturing precision
If a helical cutting path is used, then precise trajectory control is achieved minimizing bone loss, but the device complexity increases
Solution Approach 1:
The system implements a helical (curved) cutting path through the use of a guide rod with a curved or angled configuration relative to the oscillating saw blade. This curved geometry naturally guides the blade along a helical trajectory as it moves through the medullary canal, achieving precise control over the cutting path while the mechanical simplicity of the guide rod-blade assembly keeps device complexity manageable.
Data Source
AI summary
An apparatus can include an osteotome blade including an elongate main body extending from a proximal end to a distal end, the elongate main body having a curved cross-section and defining a helical path along at least a portion of a longitudinal axis of the elongate main body, wherein the distal end includes a distal cutting edge.