Bone Screw 3D Printed Thread Locking Feature
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Solution Overview
Problem
Bone screws used in orthopedic procedures often experience loosening over time due to the engagement between the internal female threading of bone plates and locking threaded portions, leading to instability and potential disassociation, which can compromise the fixation of fractures or prosthetic components.
Innovation Solution
The use of a deformable locking threaded portion on the bone screw that conforms to irregular female threading on the bone plate, formed through an additive 3D printing process, creates a secure and resistant coupling that prevents disassociation by requiring high torque for unscrewing, thereby maintaining the fixation of the bone screw to the bone and plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional threading engagement is used between bone screw and bone plate, then the assembly can be manufactured with conventional processes, but the bone screw tends to loosen over time leading to instability
Solution Approach 1:
The patent applies parameter changes by creating an irregular female threading pattern on the bone plate through 3D printing, where thread parameters (pitch, angle, depth) vary along the threading path. This irregularity causes the deformable locking threaded portion to conform uniquely to the bone plate's threading, creating a custom fit that resists loosening and enhances long-term stability.
Solution Approach 2:
The patent employs composite materials by combining a deformable locking threaded portion (made from compliant material) with the irregular female threading structure (formed from bone plate material). This composite interface allows the deformable portion to adapt to and lock into the irregular threading, creating a secure coupling that maintains fixation over time.
2Reliability
If a deformable locking threaded portion conforming to irregular female threading is created, then disassociation is prevented requiring high torque for unscrewing, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality by concentrating the irregular threading pattern specifically at the locking threaded portion interface, while the rest of the bone plate maintains conventional smooth surfaces. This localized irregularity provides the necessary conforming engagement without complicating the overall device structure or requiring complex manufacturing throughout the entire component.
Solution Approach 2:
The deformable locking threaded portion is designed to self-conform to the irregular female threading through elastic deformation during insertion. This self-conforming mechanism automatically creates the secure lock without requiring additional fastening steps, complex tooling, or post-processing, thereby managing complexity while ensuring reliable prevention of disassociation.
3Reliability
If 3D printing is used to create irregular female threading, then secure coupling is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces traditional mechanical threading systems with a 3D-printed irregular female threading structure. This substitution allows for more flexible geometry control and inherent compliance in the threading pattern, reducing the need for extremely tight manufacturing tolerances while still achieving secure coupling through the deformable locking mechanism.
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
This solution enhances the stability and longevity of the bone screw-bone plate coupling, ensuring that the bone screw remains securely attached to both the bone and the plate, even under load and movement, thereby maintaining the structural integrity and promoting healing or supporting prosthetic components effectively.
Implementation Method 1
a deformable locking threaded portion on the bone screw that conforms to irregular female threading on the bone plate
Implementation Method 2
formed through an additive 3D printing process
Implementation Method 3
laser sintering involves applying successive thin layers of powder, one layer on top of the next. Between application of each layer of powder, a laser travels over desired portions of the current powder layer and sinters targeted powder together
Data Source
Figure 1
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Figure 4
AI summary
A bone screw assembly includes a first body (130), a second body (60), and a thread locking assembly that may couple the first body with the second body. The first body includes a proximal portion (135), a distal portion that may pierce bone in response to rotation of the first body about the longitudinal axis, and a first threaded section (134) that may engage bone. The second body defines a through hole (62) that may receive the distal portion of the first body. The thread locking assembly includes a first thread locking section associated with the proximal portion of the first body, and a second thread locking section associated with the through hole of the second body. Either the first threaded locking section or the second threaded locking section deforms the other in response to rotation of the first threaded locking section relative to the second threaded locking section.