Recruitment of Tendon Crimp With Applied Tensile Strain

Abstract

The tensile stress-strain behavior of ligaments and tendons begins with a toe region that is believed to result from the straightening of crimped collagen fibrils. The in situ mechanical function is mostly confined to this toe region and changes in crimp morphology are believed to be associated with pathological conditions. A relatively new imaging technique, optical coherence tomography (OCT), provides a comparatively inexpensive method for nondestructive investigation of tissue ultrastructure with resolution on the order of 15 microm and the potential for use in a clinical setting. The objectives of this work were to assess the utility of OCT for visualizing crimp period, and to use OCT to determine how crimp period changed as a function of applied tensile strain in rat tail tendon fascicles. Fascicles from rat tail tendons were subjected to 0.5 percent strain increments up to 5 percent and imaged at each increment using OCT. A comparison between OCT images and optical microscopy images taken between crossed polarizing lenses showed a visual correspondence between features indicative of crimp pattern. Crimp pattern always disappeared completely before 3 percent axial strain was reached. Average crimp period increased as strain increased, but both elongation and shortening occurred within single crimp periods during the application of increasing strain to the fascicle.

Cruciate ligament laxity and femoral intercondylar notch narrowing in early‐stage knee osteoarthritis

“…Newly synthesized collagen, stabilized by immature crosslinks (39), is less well packed and possesses a high crimp periodicity, resulting in increased extensibility at low load (36). Because critical strain or deformation is intimately related to the extent of collagen crimp and fibril organization (34,36,49), it follows that increased laxity of the DH guinea pig ACL postmaturation is attributable to increased crimp periodicity and poor fiber alignment, perhaps due to elevated tissue turnover. In a recent study by Comerford et al (50), elevated AP knee laxity in dogs was associated with elevated MMP-2 content in the ACL.…”

A Quantitative Study of the Microstructure and Biochemistry of the Medial Meniscal Horn Attachments

“…In the toe region, the strain increases with low stress, and the crimps straightened. 13 At larger strains, passing through the heel and linear region, the collagen fibrils become straightened 23 and the stress has a significant increase compared with the first region, showing a relation between collagen crimping and bearing load of ligamentous structures. Care should be taken when interpreting data collected for strain measurements only on the proximal surface.…”

“…36 The crimp pattern of collagen has been extensively studied, and some studies have shown that collagen fibrils start uncrimping at very low tensile loads 10 and the toe region in the tensile stress-strain curve of ligaments and tendons is due to the straightening of crimped collagen fibrils. 23 In a typical stress-strain curve for ligaments and tendons we can see three regions, these are: toe, heel, and linear. In the toe region, the strain increases with low stress, and the crimps straightened.…”

Collagen V-heterozygous and -null supraspinatus tendons exhibit altered dynamic mechanical behaviour at multiple hierarchical scales

“…Tendon exhibits nonlinear biomechanical behaviour as exhibited by a typical stress -strain curve with an initial, nonlinear 'toe-region' followed by the 'linear-region' [1]. This nonlinearity, in particular the low stiffness toe-region, is thought to be attributed to a number of dynamic microstructural re-arrangements [1][2][3][4][5][6][7][8]. Particularly, the flattening or disappearance of the collagen fibre crimp morphology has been implicated in the nonlinear behaviour observed in the toe-region [9,10].…”