An In-Shoe Journey to Offload a Patient with Charcot Foot Deformity

David Sutton, Certified Pedorthist & Clinical Advisor

This particular case study was provided by David Sutton, a certified pedorthist and clinical advisor. His expertise in creating specialized footwear solutions is truly impressive.

Fig #1: Pressure mat measurement using bilateral loading. Notice the wavering PP; highly unstable.

Off-loading a Charcot foot deformity along with a fused ankle presents a unique set of challenges. It’s not just about dealing with altered foot function and shape, but also managing the history of ulcers, which can be quite daunting. These patients frequently experience anxiety and depression, coupled with lower than average muscle strength. As a result, their gait tends to lack fluidity, often characterized by their feet falling to the ground and swinging forward rather than being purposefully moved forward. Enhancing their self-esteem, motivation, and reducing their risk of falls can significantly improve compliance and help prevent further ulceration.

Given these considerations, it's crucial to design footwear that is both functional and appealing. If the footwear doesn't meet these criteria, patient compliance will likely be poor, and we won’t succeed in achieving our goals. We use in-shoe pressure mapping to ensure that peak pressures (PP) are reduced to below 200 kPa, as recommended by Schaper et al. (2019) and van Netten et al. (2017). This data provides valuable insights to the patient, often surprising them with both the outcomes and the effort involved in achieving them.

During our initial appointment, we measured the pressure distribution using a pressure mat (see Fig #1). Typically, we’d perform an in-shoe measurement, but since the patient was wearing a CAM boot on one foot and a slipper on the other, this wasn’t feasible. After reviewing the X-rays and conducting a clinical assessment of range of motion (ROM), we decided to create custom footwear and foot orthoses. Once we had a laser scan of the feet (see Fig #2), we crafted a custom-made last. A clear check fit was then created to ensure proper fit and to engage the patient in the process, providing a visual representation of the future footwear and how well it would fit.

Fig #2: 3D LASER scan of the feet for Last making in a static moment. Visible deformity in the right foot and the inclined ankle, combined with the PP from the Mat is sufficient evidence to support that this patient will fail in a prefab shoe; client has a history of failure in prefabricated footwear.

Once the ankle boot and orthoses were made, we began the in-shoe pressure mapping journey.

Data was collected from an 8-step average, with the software placing a mask over the highest peak pressure (PP) areas bilaterally. After the first in-shoe assessment (Fig #3), modifications were made to the right boot based on the collected data—5mm of thickness was added to the sole. For the left boot, the sole fulcrum was moved more proximally and a met dome was added to the orthosis. The results of these modifications were evident in the second in-shoe pressure mapping assessment (Fig #4).

Leg length discrepancies (LLD) are often overlooked, especially when considering the contralateral limb. Even a small discrepancy of 5mm can significantly impact both feet. Adding 5mm to the right boot reduced the PP loading from 335kPa to 149kPa under the base of the 5th MPJ of the right foot. However, this adjustment also affected the loading on the left heel (Fig #4).

Following the second assessment, we adjusted the left sole fulcrum further proximally and increased the met dome on the left orthosis. No further modifications were made to the right devices, though there was a slight change in loading (Fig #5). After the third assessment, the patient was sent home with specific wearing instructions. It’s common for patients to want to wear their new boots more than usual, which needs to be carefully managed to ensure long-term success.

Fig #3: First F-Scan assessment

Fig #4: Second F-Scan assessment.

Fig #5: Third F-Scan assessment, and the final outcome for the patient.

References:

Schaper, N. C., van Netten, J. J., Apelqvist, J., Bus, S. A., Hinchliffe, R. J., Lipsky, B. A., & IWGDF Editorial Board. (2020). Practical Guidelines on the prevention and management of diabetic foot disease (IWGDF 2019 update). Diabetes/Metabolism Research and Reviews, 36, e3266.

van Netten, J. J., Lazzarini, P. A., Fitridge, R., Kinnear, E. M., Griffiths, I., Malone, M., Perrin, B., Prentice, J., Sethi, S., & Wraight, P. R. (2017). Australian diabetes-related foot disease strategy 2018-2022: the first step towards ending avoidable amputations within a generation.

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