E M H Bosboom | PubMed Health

PubMed2003

Quantifying pressure sore-related muscle damage using high-resolution MRI.

To obtain insight into the etiology of deep pressure sores, understanding of the relationship between prolonged transverse loading and local muscle damage is required. To date, the amount and location of muscle damage have been determined by histological examination. In the present study, we determined whether T2-weighted high-resolution magnetic resonance imaging (MRI) can also be applied to evaluate muscle tissue after prolonged transverse loading. The tibialis anterior muscle and overlying skin in the right hindlimbs of five rats were compressed between an indenter and the tibia. The in vivo magnetic resonance images of the loaded and contralateral hindlimbs were obtained 24 h after load application. The tibialis anterior muscles were then processed for histological examination. In the magnetic resonance images of all five loaded hindlimbs, signal intensity appeared higher in the loaded regions of the muscle compared with the unloaded regions. The location of the higher signal intensity coincided with the location of damage assessed from histology. Also the amount of damage determined with MRI was in good agreement with the amount of damage assessed from histological examination. Because MRI is nondestructive, it is a promising alternative for histology in research on pressure sore etiology, especially in follow-up studies to evaluate the development of muscle damage in time and in clinical studies.

Animals↗

PubMed2003

Can loaded interface characteristics influence strain distributions in muscle adjacent to bony prominences?

Pressure distributions at the interface between skin and supporting tissues are used in design of supporting surfaces like beds, wheel chairs, prostheses and in sales brochures to support commercial products. The reasoning behind this is, that equal pressure distributions in the absence of high pressure gradients is assumed to minimise the risk of developing pressure sores. Notwithstanding the difficulty in performing reproducible and accurate pressure measurements, the question arises if the interface pressure distribution is representative of the internal mechanical state of the soft tissues involved. The paper describes a study of the mechanical condition of a supported buttock contact, depending on cushion properties, relative properties of tissue layers and friction. Numerical, mechanical simulations of a buttock on a supporting cushion are described. The ischial tuberosity is modelled as a rigid body, whereas the overlying muscle, fat and skin layers are modelled as a non-linear Ogden material. Material parameters and thickness of the fat layer are varied. Coulomb friction between buttock and cushion is modelled with different values of the friction coefficient. Moreover, the thickness and properties of the cushion are varied. High shear strains are found in the muscle near the bony prominence and the fat layer near the symmetry line. The performed parameter variations lead to large differences in shear strain in the fat layer but relatively small variations in the skeletal muscle. Even with a soft cushion, leading to a high reduction of the interface pressure the deformation of the skeletal muscle near the bone is high enough to form a risk, which is a clear argument that interface pressures alone are not sufficient to evaluate supporting surfaces.

Adipose Tissue↗