Repeatedly and consistently measuring the mechanical properties of tendon is important but presents a challenge. Preconditioning can provide tendons with a consistent loading history to make comparisons between groups from mechanical testing experiments. However, the specific mechanisms occurring during preconditioning are unknown. Previous studies have suggested that microstructural changes, such as collagen fiber re-alignment, may be a result of preconditioning. Local collagen fiber re-alignment is quantified throughout tensile mechanical testing using a testing system integrated with a polarized light setup, consisting of a backlight, 90 deg-offset rotating polarizer sheets on each side of the test sample, and a digital camera, in a rat supraspinatus tendon model, and corresponding mechanical properties are measured. Local circular variance values are compared throughout the mechanical test to determine if and where collagen fiber re-alignment occurred. The inhomogeneity of the tendon is examined by comparing local circular variance values, optical moduli and optical transition strain values. Although the largest amount of collagen fiber re-alignment was found during preconditioning, significant re-alignment was also demonstrated in the toe and linear regions of the mechanical test. No significant changes in re-alignment were seen during stress relaxation. The insertion site of the supraspinatus tendon demonstrated a lower linear modulus and a more disorganized collagen fiber distribution throughout all mechanical testing points compared to the tendon midsubstance. This study identified a correlation between collagen fiber re-alignment and preconditioning and suggests that collagen fiber re-alignment may be a potential mechanism of preconditioning and merits further investigation. In particular, the conditions necessary for collagen fibers to re-orient away from the direction of loading and the dependency of collagen reorganization on its initial distribution must be examined.
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March 2012
Research Papers
Effect of Preconditioning and Stress Relaxation on Local Collagen Fiber Re-Alignment: Inhomogeneous Properties of Rat Supraspinatus Tendon
Kristin S. Miller,
Kristin S. Miller
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
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Lena Edelstein,
Lena Edelstein
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
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Brianne K. Connizzo,
Brianne K. Connizzo
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
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Louis J. Soslowsky
Louis J. Soslowsky
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
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Kristin S. Miller
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
Lena Edelstein
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
Brianne K. Connizzo
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081
Louis J. Soslowsky
McKay Orthopaedic Research Laboratory,
University of Pennsylvania
, 424 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA, 19104-6081J Biomech Eng. Mar 2012, 134(3): 031007 (6 pages)
Published Online: March 27, 2012
Article history
Received:
September 23, 2011
Revised:
February 24, 2012
Accepted:
February 25, 2012
Posted:
March 14, 2012
Published:
March 26, 2012
Online:
March 27, 2012
Citation
Miller, K. S., Edelstein, L., Connizzo, B. K., and Soslowsky, L. J. (March 27, 2012). "Effect of Preconditioning and Stress Relaxation on Local Collagen Fiber Re-Alignment: Inhomogeneous Properties of Rat Supraspinatus Tendon." ASME. J Biomech Eng. March 2012; 134(3): 031007. https://doi.org/10.1115/1.4006340
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