Tips for making insoles!

Whilst on placement, and the podiatry degree course, we did some work on making insoles in a lab. I found two incredibly interesting articles regarding the latest insole innovation, however, I had to purchase access to both articles so I could only read a snippet of information. Instead, I’ve decided to make notes of what tips I’ve picked up from my experience in a mechanical therapy lab.

Before we get into the tips, I recommend familiarizing yourself with the materials and cover materials you need in order to make insoles.

Poron: Is a urethane foam and comes in a variety of thicknesses (3mm-6mm)

PPT: Is polyethylene material used for insoles, and also comes in a variety of thicknesses (3mm-6mm)

Poron and PPT have different levels of density and each serves its own purpose but the general rule is that for more shock absorbency, choose the denser material which is Poron (Pratt, et al., 1986).

EVA: Ethylene-Vinyl Acetate, used mostly as covers due to their softness and flexible nature (Hinz, et al. 2008).

You can see different varieties of materials in the pictures attached and take a look at different cover materials. There are more, and I'm sure I've left some out, but this is basic enough to build a foundation for your learning, especially if you study at the University of Northampton.

All pictures belong to the University of Northampton Podiatry Clinic! Enjoy the tips and I hope you find them helpful!

1) Draw an outline of the insole, cut it out, turn it over. This helps you have a marker, a guideline so to speak, on the outside. Otherwise, chances of making the insole very small are highly likely without a marker to guide you.

2) The main thing to remember about D-Fillers, which goes under the arch to support and lift it, is the thickness. Bottom layer = PPT, hardest layer goes over the top and be sure to leave a lip as long as the material is thick.

3) When making the ‘high-point of the d-filler, remember to go 2/3rds the way down. The centre point will be as medial as is the thickness of the material. For example, if the d-filler is made from 6mm ppt then the centre point will be 2/3rds the way down and 6mm inwards. If the material is 3mm, then go 2/3rds the way down and 3mm inwards, so on and so forth.

4) The most crucial piece of information you’ll ever get. ALWAYS PUT THE GLUE LID BACK ON! Many glue lives have been lost due to this recklessness

5) When using the grinder, make sure the extractor fan is on. And also, never wear an apron when using the grinder, the extractor fan will eat it up! Be very careful

6) Every component under the foot has to have a sharp edge for a smooth and seamless finish so the patient doesn’t feel any lumps and bumps.

7) Be wary of causing ‘divets’ in your d-fillers; whales; heel raises; pmp’s; and any specification you add to the insole. This can happen if there’s uneven pressure when grinding down the component. Be sure to not go “trigger-happy” whilst grinding, it is best to use the grinder slowly and go from the bottom upwards resting your hand underneath the component.

A study done by Healy et al, whose objective was to further gain insight and understanding into the characteristics of the insole material used and how they impact gait to better improve clinical decision making, concluded that medium density polyurethane material was better suited for patients with a compromised ability in plantar loading (Healy, et al., 2011). In such a case, the most obvious patients that come to mind are diabetic patients that have compromised plantar sensitivity and abnormal bony prominences that are at higher risk for developing ulceration, that will most likely benefit from insole therapy using medium-density materials (Al-Rubeean, et al., 2015).

References: These include works cited and articles I believe you will find interesting for your podiatry journey!

Al-Rubeean, K. et al., 2015. Diabetic Foot Complications and Their Risk Factors from a Large Retrospective Cohort Study. [Online] Available at: https://journals.plos.org/plosone/article/citation?id=10.1371/journal.pone.0124446 [Accessed 21 June 2021].

Armstrong, D. G. & Lavery, L. A., 1998. Diabetic Foot Ulcers: Prevention, Diagnosis and Classification. American Family Physician, 57(6), pp. 1325-1332.

Healy, A., Dunning, D. N. & Chockalingam, N., 2011. Effect of insole on lower limb kinematics and plantar pressures during treadmill walking. Prosthetics and Orthotics International, 36(1), pp. 53-62.

Hinz, P. et al., 2008. Analysis of pressure distribution below the metatarsals with different insoles in combat boots of the German Army for prevention of march fractures. Gait & Posture, 27(3), pp. 535-538.

Pratt, J. D., Rees, H. P. & Rodgers, C., 1986. Technical Note: Assessment of shock-absorbing insoles. Prosthetics and Orthotics International, 10(1), pp. 43-45.