Clinical workflow for personalized foot pressure ulcer prevention

Abstract

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.

Personalized modeling for real-time pressure ulcer prevention in sitting posture

“…This event can be related to the uncertainties induced by considering maximal strains for PU prevention. Using "cluster analysis" could overcome this limitation (see Bucki et al, 2016 for details) since it is based on the study of the largest volume of contiguous elements having a strain above a certain threshold, therefore smoothing possible misinterpretation due to a single node with a high strain value. We kept 19 pressure modes and a targeted precision of the strain field statistical reduction of 0.5 % for our second sensitivity analysis aiming at defining an optimized number of learning frames over the three sets defined earlier.…”

“…Besides porting the existing ROM technology onto a mobile platform, another technical hurdle is the ability to easily generate an accurate subject-specific biomechanical model from available medical data. To this aim, the method proposed by (Bucki et al, 2016) could be of interest and would ease the generation of the patient specific reduced model needed for each new subject.…”

Biomechanical Modeling of the Foot

“…Most of the models published in the literature are either presenting a generic model (with an average ideal morphology) or a clone of a specific patient, therefore creating only one model and avoiding the repetitiveness of the task for other patients. A solution to build rapidly new numerical clones would be to use a registration technique aiming to adapt an atlas model to the morphology of each new patient, in the same fashion as in (Bucki et al, 2016). As for the computation time, simulations are most of the time performed for a specific application, and not repeated through a daily clinical set up.…”

“…Once the full pressure is applied and equilibrium is reached, peak internal Von Mises strains have been recorded as well as the cluster volumes of soft tissues above the 20 % and 50 % strain thresholds and defining the risk of pressure ulcers. A cluster is defined as the contiguous elements having a strain peak above one of those two thresholds (Bucki et al, 2016). The aim of this study was to estimate the amount of tissues at risk in this configuration and to determine if our model could help in pressure ulcer prevention.…”

“…Finally, for a patient specific prevention, a numerical clone of the patient is needed as the morphology of the patient has a clear impact on the risk of pressure ulcer as demonstrated by (Luboz et al, 2015). Again, using the method presented in (Bucki et al, 2016) could help to reach this goal.…”