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.

Post-traumatic joint contracture (PTJC) is a debilitating condition, particularly in the elbow. Previously, we established an animal model of elbow PTJC quantifying passive postmortem joint mechanics and histological changes temporally. These results showed persistent motion loss similar to what is experienced in humans. Functional assessment of PTJC in our model was not previously considered; however, these measures would provide a clinically relevant measure and would further validate our model by demonstrating persistently altered joint function. To this end, a custom bilateral grip strength device was developed, and a recently established open-source gait analysis system was used to quantify forelimb function in our unilateral injury model. In vivo joint function was shown to be altered long-term and never fully recover. Specifically, forelimb strength in the injured limbs showed persistent deficits at all time points; additionally, gait patterns remained imbalanced and asymmetric throughout the study (although a few gait parameters did return to near normal levels). A quantitative understanding of these longitudinal, functional disabilities further strengthens the clinical relevance of our rat PTJC model enabling assessment of the effectiveness of future interventions aimed at reducing or preventing PTJC.

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.

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.

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