Surgical and Prosthetic Design | PDR | Industrial Placement

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Introduction to PDR

Prior to starting at PDR I made contact with Dominic Eggbeer (Head of Surgical and Prosthetics – PDR). Having only being given a brief synopsis of the project a few weeks prior to our initial contact I did my upmost to familiarise myself with the project.

The brief of particular interest to me was working in collaboration with PDR and Tom Wheeler (Founder of Notbroken) in the design of a mountain bike specific arm orthoses for individuals living with brachial plexus injuries. Applying my knowledge from my university experience I found justification for the project identifying a need and unraveling problems and tribulations within current products that aid rehabilitation.

I was soon introduced to Tom Wheeler who sustained a brachial plexus injury following a mountain bike accident, leaving his right arm paralysed. Competing at a high level prior to his accident provided Tom with the determination to return to his sport. He was able to talk to me about his ambitions to cycle at a competitive level again and the lack of products available to aid his recovery. Initially he began by using a sling and tackling how he could mountain bike singlehandedly. I couldn’t begin to realise the difficulties associated with balance and additional strain on his unaffected arm. This was Tom’s reasoning for developing the Not Broken arm brace, an arm brace that allows him to retain bilateral arm use whilst cycling.

The need for another arm brace

Tom’s arm brace is bespoke. Designed to comfortably fit his arm shape and size. My task was to find a way of creating a generic arm brace that worked to standardised sizes (S, M and L) and fitted a range of individuals in collaboration with PDR. Designing an arm brace that’s bespoke is expensive and time consuming for designers and patients. Through introducing something that was generic and adjustable would mean individuals could adapt it and alter it to suit their individual needs.

I knew immediately this project would challenge me, and saw it as a great opportunity to get experience in a field I hadn’t ventured into. Admittedly brachial plexus injuries aren’t common, but I didn’t see this as justification for there being no products available to aid an individuals recovery. I took on the project not only because it interested me but the end result could contribute towards helping a great deal of people get back into a sport they enjoy. Through having the support and expertise from PDR not only enabled me to apply new approaches but to have the equipment to facilitate the project.

...I was also told that PDR have cake Friday every week! So I was very quickly introduced to everyone at PDR and made very welcome, giving me the opportunity to meet people from different departments and specialties.

PDR Facilities

Further into my project at PDR I became familiarised with the software and facilities available. The software used within SPD (Surgical and Prosthetic Design) department was Freeform, software I wasn’t familiar with. It was valuable learning the potentials of Freeform and learning about what it excelled at and the diverse range of applications it could be used for. I would have valued having the time to learn a new software, however due to tight deadlines I saw sticking to familiar software was a more sensible approach in the time available. In some cases I found it useful using different software, Solidworks is more appropriate in certain applications as is Freeform and vice versa.

Freeform used within SPD was ideal for the applications they need it for. It is predominantly used for modeling implants and surgical guides for manufacture (3D printing). Prior to starting at PDR I was only familiar with desktop 3D printing (Fused Deposition Modeling – FDM) although I knew roughly how higher-grade 3D printers operated I never had the opportunity to actually use one and learn about how they worked. PDR had several SLA (Stereolithography) printers, which work off the principle of having a large vat of liquid ultraviolet light sensitive polymer resin. The printer still builds in layers but instead of being deposited like FDM printing the printer bed is submersed in the vat and the part is formed through a laser only curing the path in which the STL file has permitted. Once the part was printed I learnt about the PCA (Post Curing Apparatus) and Isopropanol used on the parts. Firstly the parts are soaked in Isopropanol, which smells like oranges! This is used to clean the parts of any excess uncured resin, the parts are then rinsed off, dried and placed in the PCA that used UV light to harden and ensure the parts are fully cured.

Overcoming Hurdles – Effective Prototype Development

Whilst being based in PDR I learnt a great deal about the applications of 3D printing. What I struggled with was determining whether 3D printing was an appropriate application for the arm brace. BPI injuries are a rarity especially those who wish to pursue cycling as a sport. Due to the rarity of the injury I found it difficult to retrieve data to determine a market size. As a result justifying appropriate manufacturing methods was hindered subsequently influencing how the arm brace progressed and how it would be designed for manufacture.

Initially I communicated my designs through low facsimile models including card tubing, PVC tubing and reverse engineering existing products. Card was ideal for gaining an idea of scale but lacked the structural integrity, preventing me gathering accurate feedback on the ideas. I struggled to find an appropriate method to develop my ideas effectively. So I looked into existing products that were designed to generic non-bespoke sizes. I came across shin guards and sports specific body armor. Inspecting them closer revealed the profile was consistent with no undulating curves that conformed to arm or shin shape. The comfortable fit was generated through the malleable EVA foam lining that forms around the limb. In response to this I began exploring ways in which a similar method could be applied to developing the arm brace. I developed a rig through reverse engineering shin guards and purchased several PVC tubes and began cutting them down to profiles that suited a range of arm shapes, this material was cheap, rigid with a degree of flex and allowed me to develop a range of models that were a high enough quality to test.

Meeting the aspirations of the end user and clinicians

Numerous prototypes later…I began exploring the aesthetical elements of the design. My research presented that a large proportion of arm specific orthoses were very clinical in appearance, very much functional and only functional! Visits to Rookwood Hospital with Dominic Eggbeer (Head of Surgical and Prosthetics – PDR) validated the cost and outcomes of some of the products developed for patients. 3D printing being a frequent occurrence in the media has raised interest within the NHS and how this groundbreaking technology could be implemented. Dominic spoke to me about the implications of introducing new processes within NHS Wales. It made me look at considerations outside of the end user. For instance if my design was sold through the NHS and it required 3D scanning as part of the process, it would be unfamiliar territory amongst clinicians and technical staff. All of these factors are influential to the product design process from how the materials are sourced, the product is designed to how it is manufactured, used and disposed of. Understanding the tribulations within the current system will aid and influence how the product is designed whist being sympathetic of how it impacts the entire system. My research whilst being based in PDR presented a model that is representative of these factors, they can be broken down into four divisions; physio-pleasure, socio-pleasure, psyco-pleasure and ideo-pleasure.

3D printing applications

Alongside learning about how 3D printing could meet aspirational needs of users, I looked into the convenience surrounding this technology. During my placement I was using CAD to generate certain parts of the arm brace. Once I had them at a certain level I could print them and test them with the user. What changed half way through my project was Tom Wheeler purchasing a 3D printer. In response to this I was able to send STL files to Tom to print, test and provide critique on. This was a quick and convenient way of gathering feedback. I began to think about how desktop 3D printing is fluctuating and the potential of designing a 3D printed arm brace that could be scaled accordingly, printed and fitted within the comfort of your home.

Although this system has the potential to work, the current quality of desktop FDM printers and the level of maintenance they require to print effectively make this system difficult to execute. It would have to ensure the arm brace was printed to a high quality eradicating the risk of its failure whilst in use, which can’t be guaranteed within household printing.

Introduction to 3D scanning applications

Following the meeting at Rookwood Hospital, Dominic and myself invited Tom Wheeler to PDR, to put 3D scanning into practice. It was all well making assumptions on whether the technology would be appropriate; I saw the best way to understand it fully was to test it and put what I had learnt into practice. Difficulties that became apparent was the duration in which Tom had to support his arm for, whilst staying stationary, scanning a 360 degree view of his arm and gathering 3D data from more concealed areas. These types of difficulties would vary from person to person from amputees to individuals with different degrees of paralysis. The advantage of 3D scanning is its ability to capture high levels of detail that couldn’t be apprehended easily through measurements. Scan data is digital allowing multiple copies to be made and shared amongst staff. When you compare this against the traditional processes being used, taking an impression of a limb can take hours sometimes days.

Rookwood Hospital – Material Applications and Manufacture

Following on from my visit to Rookwood Hospital, I was invited back by Paul Mason (Orthotic and Prosthetic Service Manager) to understand how artificial limbs and orthotic aids were produced within the NHS in a greater depth. I was introduced to the technicians and provided with the opportunity to observe the process from start to finish.

Initially the technician was provided with the patients paperwork which will cover an array of details from patient weight, height, specifications etc. These details then provide the technician with all the details required to manufacture the limb, for instance the degree of reinforcement would be influenced by patient weight etc.

The process:

  • A plaster mold is taken of the individuals limb
  • The mold is then used to vacuum form over using multiple material layups meaning materials cannot be separated to recycle
  • A pigment and resin is then added to colour the socket and bind the layers
  • This is then left under a vacuum to set
  • The plaster mold is then removed and frequently has to be broken up to release to part from the mold meaning the patient will potentially have to repeat the whole process if they need a refitting.

Although observing how prosthetics were made wasn’t directly related to my major project. There were elements that fuelled ideas and made me aware of considerations that must be accounted for within the design of the arm orthoses I’m designing, for instance; if the arm orthoses aren’t bespoke and works to generic sizes, how could an accurate and comfortable fit be achieved? Will it require patient paperwork? When thinking about manufacture, questions needed to be asked including; how can you achieve the structure integrity needed without multiple material layup and improve recyclability? How could the design be made to look less clinical?

Conflicting Information

Some of the struggles I had to try and overcome whilst on placement was conflicting information. Although I had carried out all the necessary research and testing to justify the design decisions made, I have learnt to take all advice and critique on board but instead of being indecisive learn how and whether to implement it. Group tutorials we had on a weekly basis with lecturers and classmates provided the opportunity to provide constructive criticism, suggestions and the opportunity to question the design decisions made. This very often conflicted with advice given from PDR. What I learnt from this was that no advice was wrong just merely different, the tutors intention was for me to meet the criteria of the course whilst ensuring the design could be commercialised and vice versa.

University versus Commercial

I have always been a thorough researcher from the get go, I don’t know what the project ‘need’ is until I find justification through research. What was different about my placement was the close contact I had with a commercial environment and the user. I have found university projects in the past have lacked real world applications.

Although I have learnt a great deal though my undergraduate and masters involving developing research skills and implementing them within the design process. I feel the greatest learning curve was within the last 13 weeks of my degree, where I had free reign over what I designed and the opportunity to implement what I had learnt over the past four years.

This project was challenging and unfamiliar territory for me, but it made it all the more exciting. I didn’t know what brachial plexus injuries entailed, nor a great deal about mountain biking. What interested me about this project was the amount I could learn from it and the potential to develop a really purposeful product that could aid a great deal of individuals. Not only did I have a real interest in the project, but also excellent support from Tom Wheeler and Dominic Eggbeer. I was able to gain a great deal of user insight to implement within my project on a regular basis from Tom, along with me gaining expertise on designing to meet the aspirations of individuals involved in the system along with learning about appropriate applications of current technologies.

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