Bone Graft Cannula with Helical Screw Compaction
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Solution Overview
Problem
Conventional techniques for delivering and compacting bone graft material are challenging, especially in minimally invasive procedures and small bone graft sites, such as spinal arch pedicles, where precise and efficient delivery and integration are difficult to achieve.
Innovation Solution
A tool comprising a cannula with a hopper and an output shaft featuring a helical screw thread, actuated by a mechanism that converts reciprocating linear motion into combined linear and rotary motion for efficient delivery and compaction of bone graft material, aided by a paddle for agitation and a biasing member for controlled motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional techniques are used for bone graft delivery and compaction, then the procedure can be performed with simple tools, but delivery and compaction become difficult in small and minimally invasive sites
Solution Approach 1:
The device combines multiple functions (delivery, compaction, and agitation) into a single integrated tool. The output shaft serves both as a delivery mechanism and a compaction tool, while the paddle provides agitation functionality. This merging allows the surgeon to perform all bone graft operations with one device, improving ease of operation without requiring multiple separate tools.
Solution Approach 2:
The output shaft is designed with dual functionality: it can deliver bone graft material through the cannula and simultaneously compact the material at the delivery site. The helical threads on the output shaft enable it to engage and compact bone graft pellets while maintaining the ability to deliver them. This multi-functionality addresses the contradiction by providing comprehensive capability in a single component.
2Manufacturing precision
If bone graft material is delivered to small sites like spinal arch pedicles, then minimally invasive surgery is achieved, but precise delivery and compaction become difficult
Solution Approach 1:
The device employs a nested configuration where the output shaft is positioned within the cannula, and the paddle is positioned within the hopper. This nested arrangement allows the compact device to access small surgical sites like spinal arch pedicles while maintaining the necessary precision for delivery and compaction. The nested structure enables the tool to fit within constrained surgical spaces.
Solution Approach 2:
The output shaft is designed to perform dynamic movements including rotation, axial translation, and reciprocating motion. The helical threads on the output shaft engage with bone graft material dynamically during rotation and compression strokes. This dynamic capability allows precise delivery and compaction in small sites by adapting the motion to the constrained space and material properties.
3Productivity
If the output shaft rotates continuously, then bone graft material is compacted effectively, but the actuator mechanism becomes more complex
Solution Approach 1:
The actuator mechanism employs periodic reciprocating motion rather than continuous rotation. The output shaft performs alternating forward and return strokes, with rotation occurring only during the forward compression stroke. This periodic action achieves effective compaction through repeated engagement and disengagement of the helical threads, while simplifying the actuator mechanism compared to continuous rotation systems.
Solution Approach 2:
The helical threads on the output shaft are designed to automatically engage and disengage with the bone graft material during the reciprocating motion. The threads self-load the bone graft pellets during the forward stroke and self-release during the return stroke. This self-service mechanism eliminates the need for complex external engagement systems, achieving effective compaction with a simpler actuator design.
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
Enables precise and efficient delivery and compaction of bone graft material to multiple sites, improving bone integration and screw fixation, particularly in minimally invasive surgeries like spinal procedures, with enhanced ease of use and reduced procedural complexity.
Implementation Method 1
The output shaft includes a helical screw thread extending radially outward from the output shaft toward an inner surface of the cannula. The actuator can be configured to withdraw the output shaft axially along the longitudinal axis in a direction into the hopper while rotating the output shaft for engaging bone graft material with the helical screw thread in the hopper.
Implementation Method 2
A paddle can extend radially outward from the output shaft within the internal volume of the hopper for agitating bone graft material within the hopper upon rotation of the output shaft.
Implementation Method 3
The actuator can include a bottom cam mounted relative to the hopper. A driver can be engaged for sliding linear motion relative to the bottom cam. A top cam can be mounted stationary relative to the hopper. The output shaft can include at least one cam follower configured to alternately cam with the bottom cam and with the top cam to convert reciprocating linear input movement of the driver into motion of the output shaft that alternates between linear motion extending along the longitudinal axis to push bone graft material out of the inner lumen of the cannula and combined linear and rotary motion withdrawing in a direction toward the internal volume of the hopper
Data Source
AI summary
A tool for delivery and/or compaction of bone graft material includes a cannula with an inner lumen extending along a longitudinal axis from a hopper end of the cannula to a delivery tip of the cannula. A hopper with an internal volume for storing bone graft material is connected to the hopper end of the cannula with the internal volume of the hopper in communication with the inner lumen of the cannula for delivery of bone graft material from the hopper to the delivery tip of the cannula. An output shaft within the inner lumen extends along the longitudinal axis. The output shaft includes a helical screw thread extending radially outward from the output shaft toward an inner surface of the cannula. An actuator is connected to the hopper and to the output shaft to drive the output shaft rotationally relative to the hopper and to the cannula.