Re-Design Of The Halo Frame

Abstract

The Halo frame is a medical device used to provide cranial and cervical immobilisation for patients with severe spinal injuries. It ensures proper alignment of the spine during healing by stabilising the head and neck through a combination of a halo ring attached to the skull and a vest worn on the torso. While the device is effective, its acceptance among patients and healthcare professionals has been limited.

This lack of acceptance is largely due to the unaesthetic appearance of the frame, which can have a negative psychological impact on patients, along with issues related to comfort, bulkiness, and the difficulty of assembly and adjustment. These factors often discourage patients and doctors from opting for the device, despite its clinical benefits.

The redesigned Halo frame addresses these challenges with a focus on improving aesthetic appeal, comfort, and usability. The new design minimises visual intrusion by using only two vertical rods and an additional set of horizontal rods extending over the shoulders, moving much of the structure behind the head. Carbon fibre rods and a medical-grade plastic vest were incorporated to significantly reduce the weight while maintaining structural strength. Adjustability has been enhanced with a rack-and-pinion mechanism, allowing precise height adjustments even when the patient is lying down. The design also reduces the bulk of the frame and improves the fit, ensuring it accommodates a wide range of body types.

Allowing controlled micromovements in the redesigned Halo frame supports healing by promoting natural bone stimulation, which prevents weakening over time. Research shows complete immobilisation can inhibit recovery, as seen in other orthopaedic devices like knee braces. The frame balances stability and small movements to enhance the healing process while ensuring safety.

Finite Element Analysis (FEA) was conducted to evaluate how deformation in the frame translates to deformation in the spine. Boundary conditions from existing research were used to assess whether the design meets safety and performance requirements, confirming its viability as a medical device. In the re-design, it was determined that the maximum angular displacement in the vertebrae is 6.1 degrees, and the maximum horizontal displacement between two vertebrae is 1.2 mm, confirming the design’s safety and performance.

User feedback played a significant role in refining the design. Orthopaedic technicians and design students provided valuable insights, leading to improvements such as increased adjustability of the horizontal rods and optimised hinge placement for greater accessibility. Additional considerations, such as developing reusable components and enhancing the frame’s visual appeal, aim to increase patient acceptance and sustainability.

Finally, this report outlines key recommendations for further development, including advanced performance testing under dynamic loads, prototyping with actual materials, and focused user studies to refine aesthetic appeal. Early collaboration with manufacturers is emphasised to ensure the design is cost-effective and feasible for production. Finally, steps toward MDR certification are detailed to prepare the product for market introduction.