Depth Controlled Jamshidi Needle for Spinal Surgery
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Solution Overview
Problem
Current medical instruments for spinal surgery lack the ability to accurately control the depth of penetration of Jamshidi needles into vertebrae, risking neural damage and injury to blood vessels due to the high force required to penetrate cortical bone and the danger of overshooting through cancellous bone.
Innovation Solution
A precision depth-guided instrument with an outer cannula and inner cannula system, where the inner cannula's depth is adjusted by rotating a stop on the outer cannula, allowing for controlled penetration based on pre-surgical radiography measurements to prevent over-insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a large force is applied to penetrate cortical bone, then penetration is achieved, but the risk of rapidly passing through cancellous bone and causing injury increases
Solution Approach 1:
The instrument is divided into an outer cannula and an inner cannula that can move independently. The inner cannula is advanced separately after the outer cannula penetrates the cortical bone, allowing controlled progression through the cancellous bone without applying excessive force that could cause rapid penetration and injury.
Solution Approach 2:
The inner cannula is designed to be movable within the outer cannula, allowing dynamic adjustment of penetration depth. This enables the surgeon to control the advancement of the inner cannula through the cancellous bone at a controlled rate, preventing rapid passage that could lead to injury of neural structures or blood vessels.
2Force
If a hammer or similar instrument is used to force penetration through cortical bone, then penetration is achieved, but the danger of rapidly passing through cancellous bone increases
Solution Approach 1:
The instrument separates the cortical bone penetration function (outer cannula) from the cancellous bone traversal function (inner cannula). The outer cannula can be forcefully driven through cortical bone using a hammer, while the inner cannula is then slowly and controllably advanced through the cancellous bone, eliminating the risk of rapid penetration and injury.
Solution Approach 2:
The outer cannula serves as an intermediary that first penetrates the cortical bone barrier, creating a protected pathway. The inner cannula then progresses through this protected pathway at a controlled rate, with the outer cannula acting as a guide and constraint that prevents rapid, uncontrolled advancement and potential injury.
3Length of moving object
If the inner cannula is moved further into the vertebrae without depth control, then penetration is achieved, but precise depth control is lost
Solution Approach 1:
A depth stop mechanism provides feedback control for the inner cannula advancement. The depth stop can be adjusted to predetermined depths, and when the inner cannula reaches the stop, further advancement is prevented. This ensures precise depth control and allows the surgeon to achieve the exact penetration depth required while avoiding over-penetration and injury to neural structures or blood vessels.
Data Source
AI summary
A precision depth guided instrument, such as a Jamshidi needle, is provided for use in various surgeries related to the vertebrae. The instrument includes an outer cannula, an inner cannula and a stylet. After the cortical bone of a vertebra is penetrated by the outer cannula of the instrument, the depth of penetration of the inner cannula is adjusted by rotation of a stop mounted to the outer cannula. The inner cannula is then moved further into the vertebrae, and a stop mounted on the outer cannula controls the depth of penetration of the inner cannula. The correct depth of penetration is determined by radiography prior to the procedure.