Related Experiment Video
Updated: Aug 10, 2026
07:07
Biomechanical Characterization of Human Soft Tissues Using Indentation and Tensile Testing
Published on: December 13, 2016
Evaluating the cutaneous involvement in scleroderma: torsional stiffness revisited
L R Knight1, J E Smeathers, A H Isdale
1Rheumatology and Rehabilitation Research Unit, University of Leeds, Leeds, UK.
Rheumatology (Oxford, England)
|March 21, 2001
Summary
A new device accurately measures skin stiffness in scleroderma patients, showing high reproducibility. This quantitative assessment can help evaluate disease progression and treatment response.
Area of Science:
- Dermatology
- Rheumatology
- Biomedical Engineering
Background:
- Scleroderma skin lesions correlate with internal organ involvement and disease progression.
- Accurate assessment of skin changes is crucial for prognosis and therapy evaluation.
- Quantitative measurement of skin stiffness is needed for objective assessment.
Purpose of the Study:
- To evaluate a simple device for measuring skin stiffness.
- To determine if the device can quantitatively and reproducibly assess scleroderma skin.
- To compare device measurements with the modified Rodnan clinical skin scoring technique.
Main Methods:
- Torsional skin stiffness was measured in 56 normal subjects and 42 scleroderma patients.
- Intraclass correlation coefficients (ICCs) assessed intraobserver and interobserver variability.
- Angular rotation measurements were compared between normal and scleroderma subjects and correlated with skin scores.
Main Results:
- High intraobserver (ICC > 0.90) and interobserver (ICC > 0.62) reproducibility was observed.
- Scleroderma patients showed significantly less angular rotation than normal subjects (11.3 vs 15.1 degrees).
- Angular rotation decreased significantly with increasing skin involvement severity (P<0.00001).
Conclusions:
- The skin stiffness device provides highly reproducible measurements consistent with clinical assessment.
- The device effectively distinguishes normal from sclerodermatous skin.
- Torsional stiffness measurements may be valuable for longitudinal scleroderma studies.
Related Concept Videos
01:15Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Deformation occurs in axial and transverse directions when an axial load is applied to a slender bar. This deformation impacts the cubic element within the bar, transforming it into either a rectangular parallelepiped or a rhombus, contingent on its orientation. This transformation process induces shearing strain. Axial loading elicits both shearing and normal strains. Applying an axial load instigates equal normal and shearing stresses on elements oriented at a 45° angle to the load axis.
01:10Deformation in a Circular Shaft
One of the distinctive characteristics of circular shafts is their ability to maintain their cross-sectional integrity under torsion. In other words, each cross-section continues to exist as a flat, unaltered entity, simply rotating like a solid, rigid slab. To understand the distribution of shearing stress within such a shaft, consider a cylindrical section inside this circular shaft. This section has a length of L and a radius of R, with one end fixed. The radius of the cylindrical section is...
01:20Plastic Deformation in Circular Shafts
When materials are subjected to forces that surpass their yield strength, they undergo a process known as plastic deformation. This results in a permanent alteration or strain in their structure. This concept can be specifically applied to circular shafts, where the deformation leads to a change in its shape. The precise evaluation of this plastic deformation requires understanding the stress distribution within the circular shaft, which is achieved by calculating the maximum shearing stress in...
01:10Residual Stresses in Circular Shafts
In materials that exhibit elastic and plastic behavior, known as elastoplastic materials, residual stresses can accumulate when these materials experience plastic deformation. This deformation arises from either high levels of shearing stress or significant strains. Residual stresses are internal stresses that persist within a material after removing the external force causing deformation. This phenomenon is demonstrated when observing the behavior of a shaft under torque; notably, the shaft's...
01:16Torsion of Noncircular Members
Circular shafts undergoing torsional stress maintain their cross-sectional integrity due to their axisymmetric nature. This symmetry ensures an even distribution of stress, allowing the shaft to withstand torsion without distorting. In contrast, square bars, lacking this axial symmetry, experience significant distortion across their cross-sections when subjected to torsion, with the exception of along their diagonals and at lines connecting midpoints. A detailed examination of a cubic element...
01:15Thin-Walled Hollow Shafts
In analyzing a thin-walled hollow shaft subjected to torsional loading, a segment with width dx is isolated for examination. Despite its equilibrium state, this segment faces torsional shearing forces at its ends. These forces are quantitatively described by the product of the longitudinal shearing stress on the segment's minor surface and the area of this surface, leading to the concept of shear flow. This shear flow is consistent throughout the structure, indicating a uniform distribution of...