Clinical workflow for personalized foot pressure ulcer prevention

• The presentation of a process to generate patient specific biomechanical models from an atlas for pressure ulcer prevention for the foot.
• The introduction of a new way of defining if there is a risk of pressure ulcer in the foot: monitoring the strain cluster volume.
• The results of a loading case scenario where a pressure map is applied below the foot, showing that the risk of pressure ulcer is located at different anatomical regions of the foot from one patient to the other.
• The observation that monitoring the maxim Von Mises strain is not enough to estimate the location of the highest risk of pressure ulcer. Using our criteria based on the largest strain cluster volume seems to be more effective.

Foot pressure ulcers are a common complication of diabetes because of patient's lack of sensitivity due to neuropathy. Deep pressure ulcers appear internally when pressures applied on the foot create high internal strains nearby bony structures. Monitoring tissue strains in persons with diabetes is therefore important for an efficient prevention. We propose to use personalized biomechanical foot models to assess strains within the foot and to determine the risk of ulcer formation. Our workflow generates a foot model adapted to a patient's morphology by deforming an atlas model to conform it to the contours of segmented medical images of the patient's foot. Our biomechanical model is composed of rigid bodies for the bones, joined by ligaments and muscles, and a finite element mesh representing the soft tissues. Using our registration algorithm to conform three datasets, three new patient models were created. After applying a pressure load below these foot models, the Von Mises equivalent strains and “cluster volumes” (i.e. volumes of contiguous elements with strains above a given threshold) were measured within eight functionally meaningful foot regions. The results show the variability of both location and strain values among the three considered patients. This study also confirms that the anatomy of the foot has an influence on the risk of pressure ulcer.