In vivo indentation of lower extremity limb soft tissues

Area of Science:

• Biomechanics
• Biomaterials Science
• Prosthetics and Orthotics

Background:

• Understanding the mechanical properties of residual limb soft tissues is crucial for effective prosthetic socket design.
• Previous research has often relied on ex vivo or simplified in vivo models, potentially not capturing true physiological responses.
• Trans-tibial amputation necessitates a deep understanding of the unique biomechanical challenges posed by residual limb tissues.

Purpose of the Study:

• To investigate the in vivo mechanical behavior of soft tissues in the residual limbs of individuals with trans-tibial amputation.
• To quantify the rate-dependent and nonlinear responses of these tissues under compressive loading.
• To assess the force relaxation characteristics of residual limb soft tissues.

Main Methods:

• Conducted in vivo rate-controlled indentation tests on the residual limb soft tissues of five trans-tibial amputees.
• Performed force relaxation trials under cyclic indentation loading.
• Included five nonamputees as a control group for comparative analysis.

Main Results:

• Cyclic indentation revealed that soft tissue response to compressive load is nonlinear and rate-dependent.
• Significant inter- and intrasubject variations in tissue stiffness were observed.
• Force relaxation studies showed 55-95% relaxation, with most occurring within 5 seconds post-loading.

Conclusions:

• Residual limb soft tissues exhibit complex, load-rate-sensitive mechanical properties.
• The observed force relaxation indicates significant viscoelastic behavior, important for prosthetic interface design.
• Variability in stiffness underscores the need for personalized prosthetic fitting strategies.