Biomechanics of the integumentary tissues of the human head upon in vivo dynamic loading

The success of current total knee replacement (TKR) devices is contingent on the kinematics and contact mechanics during in vivo activity. Indicators of potential clinical performance of total joint replacement devices include contact stress and area due to articulations, and tibio-femoral and patello-femoral kinematics. An effective way of evaluating these parameters during the design phase or before clinical use is via computationally efficient computer models. Previous finite element (FE) knee models have generally been used to determine contact stresses and/or areas during static or quasi-static loading conditions. The majority of knee models intended to predict relative kinematics have not been able to determine contact mechanics simultaneously. Recently, however, explicit dynamic finite element methods have been used to develop dynamic models of TKR able to efficiently determine joint and contact mechanics during dynamic loading conditions [1,2]. The objective of this research was to develop and validate an explicit FE model of a TKR which includes tibio-femoral and patello-femoral articulations and surrounding soft tissues. The six degree-of-freedom kinematics, kinetics and polyethylene contact mechanics during dynamic loading conditions were then predicted during gait simulation.

Download Full-text

Effects of CSF Properties on Brain Response Under Impact Loading

ASME 2009 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2009-206624 ◽

2009 ◽

Author(s):

M. S. Chafi ◽

V. Dirisala ◽

G. Karami ◽

M. Ziejewski

Keyword(s):

Human Head ◽

Brain Response ◽

Pia Mater ◽

Mechanical Shocks ◽

The Central Nervous System ◽

Simultaneous Loading ◽

The Impact ◽

Impact Experiments ◽

The Brain

In the central nervous system, the subarachnoid space is the interval between the arachnoid membrane and the pia mater. It is filled with a clear, watery liquid called cerebrospinal fluid (CSF). The CSF buffers the brain against mechanical shocks and creates buoyancy to protect it from the forces of gravity. The relative motion of the brain due to a simultaneous loading is caused because the skull and brain have different densities and the CSF surrounds the brain. The impact experiments are usually carried out on cadavers with no CSF included because of the autolysis. Even in the cadaveric head impact experiments by Hardy et al. [1], where the specimens are repressurized using artificial CSF, this is not known how far this can replicate the real functionality of CSF. With such motivation, a special interest lies on how to model this feature in a finite element (FE) modeling of the human head because it is questionable if one uses in vivo CSF properties (i.e. bulk modulus of 2.19 GPa) to validate a FE human head against cadaveric experimental data.

Download Full-text

Multi-layered tissue head phantoms for noninvasive optical diagnostics

Journal of Innovative Optical Health Sciences ◽

10.1142/s1793545815410059 ◽

2015 ◽

Vol 08 (03) ◽

pp. 1541005 ◽

Cited By ~ 39

Author(s):

M. S. Wróbel ◽

A. P. Popov ◽

A. V. Bykov ◽

M. Kinnunen ◽

M. Jędrzejewska-Szczerska ◽

...

Keyword(s):

Optical Properties ◽

Near Infrared ◽

Optical Measurement ◽

Human Head ◽

Medical Diagnostics ◽

Optical Parameters ◽

Measurement Systems ◽

Tissue Phantoms ◽

Optical And Mechanical Properties

Extensive research in the area of optical sensing for medical diagnostics requires development of tissue phantoms with optical properties similar to those of living human tissues. Development and improvement of in vivo optical measurement systems requires the use of stable tissue phantoms with known characteristics, which are mainly used for calibration of such systems and testing their performance over time. Optical and mechanical properties of phantoms depend on their purpose. Nevertheless, they must accurately simulate specific tissues they are supposed to mimic. Many tissues and organs including head possess a multi-layered structure, with specific optical properties of each layer. However, such a structure is not always addressed in the present-day phantoms. In this paper, we focus on the development of a plain-parallel multi-layered phantom with optical properties (reduced scattering coefficient [Formula: see text] and absorption coefficient μa) corresponding to the human head layers, such as skin, skull, and gray and white matter of the brain tissue. The phantom is intended for use in noninvasive diffuse near-infrared spectroscopy (NIRS) of human brain. Optical parameters of the fabricated phantoms are reconstructed using spectrophotometry and inverse adding-doubling calculation method. The results show that polyvinyl chloride-plastisol (PVCP) and zinc oxide ( ZnO ) nanoparticles are suitable materials for fabrication of tissue mimicking phantoms with controlled scattering properties. Good matching was found between optical properties of phantoms and the corresponding values found in the literature.

Download Full-text