Development of new locking mechanism for mini-fragment hand plates for small bone fracture fixation

Author: Jesvin Varghese

Varghese, Jesvin, 2021 Development of new locking mechanism for mini-fragment hand plates for small bone fracture fixation , Flinders University, College of Science and Engineering

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Hand anatomy comprises of intricate and complex features which could be affected by various disorders and traumatic injuries. Some of these injuries are mild and some can be very serious. Fracture that are less severe are treated using splints or cast which stabilises the fracture over a few days or weeks depending on the degree of severity. However, there are more severe fractures that would not be treated by solely using cast and splints. These fractures that may have serious dislocations require surgical treatment that involves using plates, screws and pins to stabilise the fractures. The patients are assessed using various recognised ways such as Disabilities of Arm, Shoulder and Hand (DASH) score to assess the performance of implant as well as to identify any potential complications. This project was completed under the requirements of Austofix Pty Ltd, an Australian recognised manufacturer and supplier of orthopaedic devices. The primary clients of the products are hand surgeons of Macquarie University Hospital, based in Sydney. The aim of this project is to develop a locking mechanism for mini-fragment plates that can be used across metacarpals and phalanges of hand.

Based on the clinical literature review conducted, it was identified that the current state of art for hand fractures is hand plates and screws with variable angle screw technology. Based on this research, it was decided that three types of Variable Angle Screw Technology (VAST) buttons and one 1.5 mm locking screw with M2.3x0.45 locking head were designed with necessary jigs needed for testing. The three types of buttons designed are threaded parallel button, threaded tapered button and spline button. All parts were designed and analysed using Solidworks.

Changes were made to the design based on the analysis completed in Solidworks that assessed the interaction between the VAST buttons and the locking screw. After the final designs were finalised, all technical drawings were completed in Solidworks with adequate tolerancing. The drawings have been approved by the technical design coordinator at Austofix and sent to the manufacturer expected to arrive in late October/ early November for mechanical testing.

There have been limitations in this project with the Covid-19 pandemic that has occurred as well as technical limitations due to lack of experience in technical file management as well as manufacturer limitations. After the testing the parts and achieving satisfactory results, this project has a great scope for future work. The future work of this project will involve implementing this developed locking system in mini-fragment hand plates which alone will require a significant amount of research and concept designs.

Keywords: Hand Fracture, Orthopedic devices, hand fracture fixation, Mini-fragment hand plate

Subject: Engineering thesis

Thesis type: Masters
Completed: 2021
School: College of Science and Engineering
Supervisor: John Costi