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

David Sutton, Certified Pedorthist & Clinical Advisor

The following case study was provided by David Sutton, a certified Pedorthist and clinical advisor.

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

Off-loading a Charcot foot deformity and a fused ankle presents a unique set of challenges. It's not just about dealing with the altered biomechanics and the changed shape of the foot, but also managing the history of ulcers, which often leads to anxiety and depression among these patients. Their muscle strength tends to be lower than average, causing their gait to be less fluid. Instead of moving forward in a purposeful manner, their feet often just drop and swing forward. This impacts their self-esteem and increases their risk of falls, which can lead to non-compliance and potential worsening of ulcers.

Considering all these factors, our priority is to create footwear that is functional, easy to wear, and aesthetically pleasing. If we can't achieve this, compliance will suffer, and ultimately, we'll have failed in our mission. We use in-shoe pressure mapping to ensure that peak pressure (PP) is reduced to below 200kPa, as recommended by Schaper et al. (2019) and van Netten et al. (2017). The data generated from this process is invaluable when explaining the outcomes to patients. Many times, patients may not feel immediate changes, but seeing the data helps them understand the progress being made.

During our initial appointment, we measured pressure distribution using a pressure mat (see Fig #1). Normally, we would conduct an in-shoe measurement, but the patient was wearing a CAM boot on one foot and a slipper on the other, making this irrelevant. Combining this data with X-rays and a clinical assessment of range of motion (ROM), we decided to create custom footwear and foot orthoses. Once a 3D laser scan of the feet was completed (see Fig #2), we developed a custom-made last. From there, we created a clear check fit to confirm proper fit and involve the patient in the process by showing them a visual representation of the footwear design.

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.

With the ankle boots and orthoses complete, we began the in-shoe pressure mapping process.

Data was collected from an average of eight steps, with the software creating a mask over the highest peak pressure (PP) area bilaterally. After the first in-shoe assessment (see Fig #3) in the new custom footwear and orthoses, modifications were made to the right boot based on the data collected—adding 5mm 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 can be seen in the second in-shoe pressure mapping assessment (see Fig #4).

Leg length discrepancies (LLDs) are frequently overlooked, especially when it comes to the contralateral limb. Even a small discrepancy of 5mm can significantly impact both feet. By adding 5mm to the right boot, we reduced the peak pressure loading under the base of the 5th metatarsophalangeal joint (MPJ) of the right foot from 335kPa to 149kPa. However, this adjustment also affected the loading on the left heel (see Fig #4).

Following the second assessment, further modifications were made to the left sole fulcrum, moving it further proximally, and the met dome on the left orthosis was increased. No additional modifications were made to the right devices, though there was a slight change in loading observed (see Fig #5). After the third assessment, the client was sent home with specific wearing instructions. It’s common for patients to push themselves too hard after receiving new footwear, so moderation is key to achieving 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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