Journal of Mechanics in Medicine and Biology

This paper presents a blood-perfused skin model as implemented in a spreadsheet software application for accessing burn injuries resulting from exposure of skin surface to flowing hot fluids or constant heat sources. Finite-difference analysis of heat transfer in skin burns provides an accurate prediction of tissue time–temperature relationships throughout the duration of thermal insult. The Henriques theory of skin burns is used for determining the spatial and temporal extent of tissue damage. The epidermis, dermis, and subcutaneous fat were modeled as uniform elements with distinct thermal properties. Method for implementing finite-difference solution in spreadsheet software has been described. A comparison of the injury threshold computed by this model against Henriques's result has been done and the results are in good agreement.

A CFD (Computational Fluid Dynamics) model was developed to simulate flow in a membrane oxygenator. The hollow fiber bundles were treated as a porous medium. This study demonstrated that the numerical model could accurately predict the distributions of flow velocity, pressure, shear stresses, temperature, and oxygen concentration in the device. The numerical model is a powerful tool for the designing of a membrane oxygenator.

Modification of the surface chemistry, topography, and frictional characteristics of medical-grade low linear-density polyethylene catheters with various plasma chemistries was accomplished in a radio-frequency (RF) vacuum chamber. Two different types of plasma treatments were examined. For surface texturing and chemistry modification, the catheters were treated with either He or CF₄ gases for 0.5–60 min at RF power in the range of 30–1000 W and working pressure between 0.2 and 2 Torr. For grafting of a low friction film, the catheters were exposed to pure Ar plasma at 400 W for 2 min (surface cleaning) and then to CH₄, CH₄/CF₄, or H₂/CF₄ plasmas at power of 250–550 W and working pressure of 0.2–0.8 Torr for 10–60 min (surface modification). The effects of the different plasma treatments on the surface texture, chemical behavior, and friction characteristics of the catheters are discussed in light of results obtained from contact surface profilometry, scanning electron microscopy, atomic force microscopy, contact angle measurements, infrared spectroscopy, and friction experiments. The findings of this study demonstrate that surface crosslinking and grafting of desirable functional groups by RF plasma treatment is an effective low-temperature surface modification technique for polymeric medical devices.

Quantification of biomechanical parameters by describing interactions between a wheelchair user and his cushion is important to prevent pressure sores in a better way and to match the needs of the subjects in terms of comfort and mobility. This paper presents the method and the results of a biomechanical analysis through the pressure maps at the body–seat interface of a antidecubitus wheelchair cushion on a group of eight patients (affected by SCI or Multiple Sclerosis) during autonomous wheelchair propulsion. In general, our results confirm that mobility is an important factor for ulcer prevention because passing from the static sitting posture to propulsion the mean pressure decreases and there is a redistribution of the load at lower pressure values. Moreover this represents a useful approach for the customized choice and adaptation of the antidecubitus aids.

In this paper, a numerical procedure for obtaining a cutting performance "signature" for a bur is proposed. This procedure is applied to a comparative analysis of the cutting performance of a surgical bur under various operating conditions. An experimental method, which uses a constant feed rate and measures feed force, is utilized to perform tests leading to the data needed for the aforementioned procedure. Several proof-of-concept tests are performed and their results are presented. The proposed approach shows capability for tracking the cutting performance of a bur as it gets duller.

Falls among the elderly are a common occurrence and the incidence rate is increasing with our aging population. In such a population, a fall may precipitate a femoral neck fracture which may be treated by any one of a variety of femoral screw/plate mechanisms. Unfortunately, such mechanisms can fail in service as the device migrates proximally eventually requiring a secondary and more invasive surgery. In the current study we propose a new design to address this failure mechanism and we use a simple finite element model to study a modification to the current design.

Trauma victims suffering massive soft tissue wounds are at increased risk for infection. This is typically addressed by placing antibiotic impregnated bone cement into the tissue defect to provide a massive prophylaxis directly to the affected site. The cement–antibiotic mixture is typically "pasted" onto a length of suture by the surgeon. Unfortunately, this process is sometimes difficult to perform in the operating room environment due to difficulty in localizing the mixture on the suture. In addition, the surgeon must perform the process within a relatively short time constraint as the mixture hardens. In the current study we address this issue by proposing a unique molding design which is lightweight, cost effective, disposable, and suitable for use in the operating room environment.