Experimentally measured lumbar skin strains during functional movements

Area of Science:

• Biomechanics
• Wearable Technology
• Spinal Kinematics

Background:

• Skin-adhered wearables show potential for continuous spinal kinematics monitoring.
• Assessing spine-related issues like low-back pain relies on understanding skin deformation.
• Designing effective lumbar wearables is hindered by limited data on skin strain during movement.

Purpose of the Study:

• To quantify dynamic, inhomogeneous, and anisotropic strain fields of lumbar skin during various movements.
• To provide essential data for the design of more precise spinal-specific wearables.
• To explore the clinical relevance of lumbar skin strain in surgical and wound care contexts.

Main Methods:

• Measured skin motion using a dense grid of reflective markers during uniplanar, multiplanar, and activities of daily living (ADL) movements.
• Computed dynamic strain fields based on large deformation strain theory.
• Analyzed strain magnitudes, orientations, sex-based differences, and repeatability.

Main Results:

• Macroscopic principal strains reached averages as high as 103% during Flexion, with strain rates up to 151%/second.
• Principal strain orientations were dependent on the specific movement.
• Males exhibited higher principal strains than females during Flexion and Sit To Stand motions; high repeatability was observed across movements.

Conclusions:

• Lumbar skin strain fields are influenced by spinal geometry and dermal collagen fiber orientation.
• Results are critical for enhancing the precision of spinal wearables placed on different lumbar regions.
• Findings may inform surgical incision orientation and wound care strategies in the lumbar area.