Orthotic therapy has been around for many years. In the 26 years I have been prescribing and building orthotic devices, the technology and underlying prescription process has changed enormously. The standard building blocks of orthotic design when I entered University in 1996 were polypropylene plastic shells linked to static lower leg measurements to decide correction levels. These concepts were diligently instructed and practised by Podiatrists for many years.
When I moved back to Hobart in 2007, I got stuck into orthotic creation again in the orthotic lab at our practice. Whilst some of the concepts around orthotic prescription had begun to move on, the underlying materials remained largely unchanged. Most were made from polypropylene shells or EVA foam blocks. It was around this time we began designing orthotics for cycling. This was a huge change in design parameters as the volume and shape required to fit appropriately inside a tight fitting cycling shoe were very unique. We experimented with thin plastics and foams however we found this was still too bulky.
Carbon Fibre Orthotic
We started using a carbon fibre composite around this time to keep the volume down. The first carbon fibre we used was thermo-mouldable and was a simple twill layout. Whilst the volume was more appropriate, the uniform layup of the fibre didn’t allow us to reinforce the shells in the direction where the maximum load was occuring.
After a lot of experimenting, we began layering up our own carbon fibre and baking our shells with different types of carbon weave. This significantly reduced the volume further and allowed us to create strength in directions where we wanted it. It also allowed the shells to bend and flex under load rather then remain a uniform shape.
Cycling shoes have very little space for orthotics
This brings us back to the prescription process and why we love using the carbon fibre for its unique properties. Whether we ride or run, our feet don’t remain a fixed shape under load. The natural tendency is for a foot to change shape through the riding/running process. Carbon fibre flexibility works well with the dynamic nature of this crucial foot function. If your arch flattens under load, we should expect the orthotic shell adapt to this change rather than remain stiff and unyielding.
The overall outcome is a more comfortable lightweight thin orthotic device that tends to be more user friendly and less obtrusive. It doesn’t mean that every orthotic device is the same, or that every version we create is perfect every time, but certainly we try and create solutions with dynamic loading in mind, and the client expectations at the heart of the solution, As I always say, “there is no point in having the ‘best’ orthotic device available to you if it sits in the cupboard not being used”.