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Connective tissues, such as tendons, ligaments, and capsules, play a large role in locomotion and joint stability and are often subjected to traumatic injuries and degeneration. The purpose of this study was to evaluate if the mechanical and microstructural properties of connective tissues correlate with the age and sex of the human donor. Dissected samples were prepared for mechanical testing, consisting of 10 cycles of preconditioning, a stress‐relaxation ramp and hold, and a quasi‐static ramp to failure. During the testing protocol, the microstructural organization of tissues was analyzed using quantitative polarized light imaging. A linear mixed model was used to assess whether tissue type, donor age, or donor sex were significantly associated with mechanical and microstructural tissue properties. Tissue type had a significant effect on all parameters, while donor age and sex did not. Groupings by tissue type (i.e., tendon vs. ligament vs. capsule) were evident for microstructural data, with tendons having a tighter grouping and ligaments having a larger spread of values. The interaction of tissue type and age yielded a significant effect for linear modulus only (p = 0.007), with the palmaris tendon appearing to have the largest contribution to this effect. There were no significant interaction effects between sex and tissue type or donor age. Donor age appears to affect linear modulus in some, but not all, tissue types. Otherwise, age and sex do not have significant effects on the mechanical and microstructural properties of the range of connective tissues that were analyzed in this study. [ABSTRACT FROM AUTHOR]

Posttraumatic joint contracture (PTJC) is a debilitating condition characterized by loss of joint motion following injury. Previous work in a rat model of elbow PTJC investigated disease etiology, progression, and recovery in only male animals; this study explored sex‐based differences. Rat elbows were subjected to a unilateral anterior capsulotomy and lateral collateral ligament transection followed by 42 days of immobilization and 42 days of free mobilization. Grip strength and gait were collected throughout the free mobilization period while joint mechanical testing, microcomputed tomography and histological analysis were performed postmortem. Overall, few differences were seen between sexes in functional, mechanical, and morphological outcomes with PTJC being similarly debilitating in male and female animals. Functional measures of grip strength and gait showed that, while some baseline differences existed between sexes, traumatic injury produced similar deficits that remained significantly different long‐term when compared to control animals. Similarly, male and female animals both had significant reductions in joint range of motion due to injury. Ectopic calcification (EC), which had not been previously evaluated in this injury model, was present in all limbs on the lateral side. Injury caused increased EC volume but did not alter mineral density regardless of sex. Furthermore, histological analysis of the anterior capsule showed minor differences between sexes for inflammation and thickness but not for other histological parameters. A quantitative understanding of sex‐based differences associated with this injury model will help inform future therapeutics aimed at reducing or preventing elbow PTJC. [ABSTRACT FROM AUTHOR]

Background: The anteromedial (AM) bundle of the anterior cruciate ligament (ACL) has a higher modulus and failure stress than does the posterolateral (PL) bundle. However, it is unknown how these properties vary within each bundle. Purpose: To quantify mechanical and microstructural properties of samples within ACL bundles to elucidate any regional variation across the ligament. We hypothesized that there are no differences within each bundle in contrast to cross-bundle variation. Study Design: Descriptive laboratory study. Methods: Sixteen human ACLs were dissected into AM and PL bundles. Three samples were taken from each bundle in an ordered sequence from AM (region 1 AM bundle) to PL (region 6 PL bundle). Each sample was tested in uniaxial tension, using quantitative polarized light imaging (QPLI) to quantify collagen fiber alignment. After preconditioning, samples were subjected to a stress-relaxation (SR) test followed by quasistatic ramp-to-failure (RF). Peak and equilibrium stress values were computed from the SR test and modulus quantified in the toe- and linear-regions of the RF. QPLI values describing collagen orientation (angle of polarization [AoP]) and strength of alignment (degree of linear polarization [DoLP]) were computed for the SR test and at points corresponding to the zero, transition point, and linear region of the RF. Results: Toe- and linear-region modulus values decreased from region 1 to 6. Slopes of regression lines increased for the average DoLP during RF, with significance at higher strains. The standard deviation of AoP values decreased during RF, indicating tighter distribution of orientation angles, with significant correlations at all points of the RF. During SR, stress values uniformly decreased but did not show significant linear regression by region. DoLP and AoP values changed slightly during SR and demonstrated significant linear variation by region at both peak and equilibrium points. Conclusion: Most microstructural and material properties evaluated in this study appear to follow a linear gradient across the ACL, rather than varying by bundle. Clinical Relevance: This AM-to-PL variation provides a more accurate description of functional tissue anatomy and can be used to assess and guide techniques of ACL reconstruction. [ABSTRACT FROM AUTHOR]