An MRI compatible loading device for the reconstruction of clinically relevant plantar pressure distributions and loading scenarios of the forefoot

MR-compatible loading device for assessment of heel pad internal tissue displacements under shearing load

In the last decade, the role of shearing loads has been increasingly suspected to play a determinant impact in the formation of deep pressure ulcers. In vivo observations of such deformations are complex to obtain. Previous studies only provide global measurements of such deformations without getting the quantitative values of the loads that generate these deformations. To study the role that shearing loads have in the etiology of heel pressure ulcers, an MR-compatible device for the application of shearing and normal loads was designed. Magnetic resonance imaging is a key feature that allows to monitor deformations of soft tissues after loading in a non-invasive way. Measuring applied forces in an MR-environment is challenging due to the impossibility to use magnetic materials. In our device, forces are applied through the compression of springs made of polylactide. Shearing and normal loads were applied on the plantar skin of the human heel through a flat plate while acquiring MR images. The device materials did not introduce any imaging artifact and allowed for high quality MR deformation measurements of the internal components of the heel. The obtained subject-specific results are an original data set that can be used in validations for Finite Element analysis and therefore contribute to a better understanding of the factors involved in pressure ulcer development.

An Innovative Weightbearing Device for Weightbearing 3-Dimensional Imaging for Foot and Ankle Surgery Preoperative Planning

Three-dimensional preoperative planning has demonstrated multiple surgical advantages. Currently, we cannot carry out preoperative 3-dimensional planning of foot and ankle orthopedics in most hospitals due to the impossibility of performing weightbearing CT imaging. Our objective is to describe and evaluate an innovative accessible, simple, and effective device that simulates standing while in a supine position, to obtain 3-dimensional images supporting bodyweight load with a conventional CT machine. From a group of 30 volunteers, 10 patients were randomly selected and pressure and its distribution were analyzed while in a standing position in both feet. Differences between both feet were considered normal intrapersonal variability. Subsequently, the right footprint of the same 10 subjects was evaluated in the proposed loading device. Then, their pressures and distribution were compared with respect to standing and with respect to intrapersonal variability. The mean total standing pressure was 93 Kpa (standard deviation [SD] 14.32), which was reduced to 81.95 Kpa (SD 19.54) in the loading device. The load device reduced the pressure by a mean of16% (SD 22% (range -25% to -0.03%). At the hindfoot level, the loading device increased pressure by a mean of 20.59 Kpa, which expressed percentage implies an increase of 14% compared to standing. Due to its easy construction and effectiveness, this is the first device that opens the door of foot and ankle orthopedics in any hospital to 3D preoperative planning and the benefits derived from it.