Geared Joint Reamer for Minimally Invasive Fusion Preparation
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Solution Overview
Problem
Existing minimally invasive procedures for metatarsal-phalangeal joint fusion face challenges such as the need for open dislocation, use of burrs that shorten bones, and lack of guidance, leading to irregular surfaces and incomplete debridement.
Innovation Solution
A geared instrument with a shaft and reamer system, where rotation of the shaft causes non-parallel rotation of the reamer, allowing precise removal of cartilage and bone through a minimally invasive approach, using a distractor to maintain bone positioning and facilitate simultaneous preparation of both bones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If burrs are used for minimally invasive cartilage removal, then the procedure can be performed minimally invasively, but the burrs remove bone in addition to cartilage leading to bone shortening and require freehand technique with little guidance
Solution Approach 1:
A guide instrument is introduced as an intermediary device that interfaces between the burr and the surgeon's control. The guide instrument includes a shaft with a specific curvature that allows it to navigate through the minimally invasive access point and position the burr precisely at the joint location, providing mechanical guidance while maintaining minimal invasiveness
Solution Approach 2:
The shaft of the guide instrument is designed with a specific curvature parameter that changes its orientation in space. This curvature allows the instrument to transition from a minimally invasive entry point to the precise location within the joint, enabling controlled burr positioning without requiring complete joint dislocation
2Manufacturing precision
If open procedure with full dislocation is used, then precise cartilage removal can be achieved, but complete joint dislocation is required which increases procedural complexity
Solution Approach 1:
The guide instrument utilizes a curved shaft geometry that operates in three-dimensional space, allowing the surgeon to access the joint through a minimally invasive path. The curvature of the shaft creates a spatial transformation that bypasses the need for direct linear access through complete joint dislocation
3Ease of operation
If freehand technique is used with burrs, then minimally invasive approach is maintained, but there is risk of incomplete joint debridement or creation of irregular surfaces
Solution Approach 1:
The guide instrument serves as a mediator between the surgeon's intent and the burr's action. It provides mechanical constraints and guidance features that ensure the burr follows the correct trajectory and maintains proper orientation, thereby ensuring complete and uniform cartilage removal while preserving the minimally invasive approach
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 preparation of the metatarsal-phalangeal joint for fusion without complete dislocation, reducing complications and shortening, and allowing for simultaneous bone preparation, thus enhancing procedural accuracy and efficiency.
Implementation Method 1
a first gear coupled to the first end of the shaft such that rotation of the shaft about the first axis causes rotation of the first gear about the first axis. The instrument further includes a second gear enmeshed with the first gear
Implementation Method 2
Rotation of the shaft about the first axis causes rotation of the reamer about a second axis that is non-parallel with the first axis such that, with the instrument at least partially disposed in a joint space between a first bone and a second bone, rotation of the reamer removes material from the joint space
Data Source
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AI summary
A system includes an instrument and a distractor. The instrument includes a shaft extending from a first end to a second end and defining a first axis between the first end and the second end. The instrument further includes a first gear coupled to the first end of the shaft. The instrument further includes a second gear enmeshed with the first gear. The instrument further includes a reamer coupled to the second gear. Rotation of the shaft about the first axis causes rotation of the reamer about a second axis that is non-parallel with the first axis. The distractor includes a first arm defining a first passage and a second arm defining a second passage, each configured to receive a pin. The distractor further includes a retainer configured to engage the instrument to retain the instrument in position. The distance between the first passage and the second passage is adjustable.