Temporal Effects of Mechanical Loading on Deformation-Induced Damage in Skeletal Muscle Tissue

Abstract

Mechanical loading of soft tissues covering bony prominences can cause skeletal muscle damage, ultimately resulting in a severe pressure ulcer termed deep tissue injury. Recently, by means of an experimental-numerical approach, it was shown that local tissue deformations cause tissue damage once a deformation threshold is exceeded. In the present study, the effects of load exposure time and intermittent load relief on the development of deformation-induced muscle damage were investigated. The data showed that a 2 h loading period caused more damage than 10 min loading. Intermittent load reliefs of 2 min during a 2 h loading period had minimal effect on the evolution of skeletal muscle damage. In addition, a local deformation threshold for damage was found, which was similar for each of the loading regimes applied in this study. For short loading periods, these results imply that local tissue deformations determine whether muscle damage will develop and the exposure time influences the amount of tissue damage. Temporary load reliefs were inefficient in reducing deformation-induced damage, but may still influence the development of ischemia-induced damage during longer loading periods.

A novel MRI compatible soft tissue indentor and fibre Bragg grating force sensor

“…9. Many current soft tissue loading devices for the MRI environment do not have dynamic force displacement control capabilities and have been limited to quasi-static deformation analysis [18,21,22,24,26,28,29], the evaluation of isotropic hyperelastic constitutive models [18,21,22,24,26,28,29], estimation of strain from 2D imaging [21,27,28] or from finite element simulations [21,22].…”

“…[16,17]) and the study of pressure ulcer development (e.g. [18][19][20][21][22][23]). In addition, as is relevant here, they have been employed for non-invasive investigation of soft tissue biomechanics (e.g.…”

“…[26]) or finite element analysis (FEA) for estimation of deformation instead (e.g. [21,22]). However these measures are more limited than full 3D deformation measurement based on SPAMM tagged MRI [3].…”

“…In addition the studies employing soft tissue loading devices have limited their analysis to the evaluation of isotropic hyperelastic constitutive models (e.g. [18,21,22,24,26,28,29]). Evaluation of more detailed constitutive models incorporating non-linearity, viscoelasticity and anisotropy require more detailed boundary condition measurement which is the focus of the current study.…”

Distribution of Internal Strains Around Bony Prominences in Pigs

“…45,63,68 Measurements of strain due to external loading have also been obtained from studies in rats using MRI tagging techniques. 44 The main goal of this study was to determine the levels of strain in different regions of the muscle surrounding the ischial tuberosities in adult, healthy pigs as a result of varying levels of external loading. We also assessed the effect of muscle atrophy secondary to chronic SCI on the distribution of strain magnitudes in one animal, and determined the effect of DTI on the distribution of strain magnitudes in another animal with SCI and DTI.…”