Minimal Incision Bone Screw with Segmented Head for Easy Removal
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Solution Overview
Problem
Current bone screws are difficult to remove due to creeping fibrosis, which complicates access and requires significant effort and trauma, and there is a need for a solution that allows for easy placement and removal without pre-drilling or tapping, especially for metal screws that may cause long-term deleterious effects or interfere with electromagnetic technologies.
Innovation Solution
A bone screw design featuring a self-tapping thread, a convex bone-engaging compression member, and a non-circular head that can be easily accessed and driven with a simple screwdriver, allowing for easy placement and removal, with a cannulated option for precise placement and minimal tissue trauma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bone screws are used, then reliable bone fixation is achieved, but removal becomes difficult due to creeping fibrosis requiring significant effort and tissue trauma
Solution Approach 1:
The screw is divided into distinct segments: a threaded portion for bone engagement and a separate head portion with drive interface. This segmentation allows the threaded portion to remain embedded in bone for reliable fixation while the head portion can be accessed through minimal incision for easy removal using a driver tool.
Solution Approach 2:
The design extracts the drive interface from the threaded portion, separating the functions of bone engagement and tool interaction. The head portion with its drive interface can be removed through minimal incision without requiring removal of the entire screw assembly, significantly easing the removal process.
2Stability of the object's composition
If conventional bone screws are used, then stable fracture fixation is achieved, but placement requires pre-drilling and tapping increasing procedure complexity
Solution Approach 1:
The screw features self-tapping threads that cut their own path through the bone during insertion, eliminating the need for separate pre-drilling and tapping operations. The threaded portion automatically creates the necessary bone engagement as the screw is driven into place, simplifying the placement procedure while maintaining stable fixation.
3Strength
If metal screws are used, then strong bone fixation is achieved, but long-term deleterious effects and electromagnetic interference occur
Solution Approach 1:
The patent enables parameter changes in material composition by allowing selection between metal and non-metallic materials. The screw can be manufactured from non-conductive materials such as polymers or ceramics that maintain sufficient mechanical strength for bone fixation while eliminating electromagnetic interference and long-term deleterious effects associated with metal implants.
4Reliability
If conventional bone screws are used, then adequate fixation is achieved, but removal requires large incisions and significant tissue trauma
Solution Approach 1:
By segmenting the screw into a threaded portion and a separate head portion, the design enables removal through minimal incision that only needs to access the head portion. The threaded portion remains in the bone providing adequate fixation, while the head can be extracted through a small incision without requiring large tissue exposure or significant tissue trauma.
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 easy placement and removal of bone screws with reduced tissue trauma and minimal incision, facilitating bone regeneration and accommodating various bone types and anatomical needs, while being suitable for both placement and removal without the need for pre-drilling or tapping.
Implementation Method 1
the threads on the distal end extend only far enough to ensure a positive grip in the distal fragment but not so far as to engage the proximal fragment when the screw is applied
Implementation Method 2
The distal side of the head, facing the shaft, is usually symmetrically convex, preferably hemispherical, and the proximal face of the proximal bone fragment is frequently lightly countersunk, in order to spread stresses in the screw and the bone most efficiently, to reduce the risk of creating a stress fracture
Implementation Method 3
Cortical screws have fine threads on their shaft and are designed to anchor in cortical bone. Cancellous screws tend to have coarser threads and are designed to anchor in the softer cancellous bone.
Data Source
AI summary
A surgical bone screw (1) and driver (31), and a method for using them for repairing an osteotomy or fracture. The screw has a shaft having a head (5) at its proximal end, screw threads (3) at its distal end and a compression member (7) between the head and the screw threads. In an embodiment, the threads are self-tapping and self-drilling, the head is polygonal, and the sides of the polygon are convex. The driver turns the screw until the threads cross a fracture site and the compression member contacts the proximal bone fragment. The threads and compression member draw the fragments together and leaves the head entirely clear of the bone surface. The screw is removed through a small incision. Tilting the driver to allow the socket to engage an inwardly extending lower portion of the head permits the driver to lift the screw out of the bone.