Achilles Tendon Loading during Running Estimated Via Shear Wave Tensiometry: A Step Toward Wearable Kinetic Analysis.

PURPOSE: Understanding muscle-tendon forces (e.g., triceps surae and Achilles tendon) during locomotion may aid in the assessment of human performance, injury risk, and rehabilitation progress. Shear wave tensiometry is a noninvasive technique for assessing in vivo tendon forces that has been recently adapted to a wearable technology. However, previous laboratory-based and outdoor tensiometry studies have not evaluated running. This study was undertaken to assess the capacity for shear wave tensiometry to produce valid measures of Achilles tendon loading during running at a range of speeds. METHODS: Participants walked (1.34 m·s -1 ) and ran (2.68, 3.35, and 4.47 m·s -1 ) on an instrumented treadmill while shear wave tensiometers recorded Achilles tendon wave speeds simultaneously with whole-body kinematic and ground reaction force data. A simple isometric task allowed for the participant-specific conversion of Achilles tendon wave speeds to forces. Achilles tendon forces were compared with ankle torque measures obtained independently via inverse dynamics analyses. Differences in Achilles tendon wave speed, Achilles tendon force, and ankle torque across walking and running speeds were analyzed with linear mixed-effects models. RESULTS: Achilles tendon wave speed, Achilles tendon force, and ankle torque exhibited similar temporal patterns across the stance phase of walking and running. Significant monotonic increases in peak Achilles tendon wave speed (56.0-83.8 m·s -1 ), Achilles tendon force (44.0-98.7 N·kg -1 ), and ankle torque (1.72-3.68 N·m·(kg -1 )) were observed with increasing locomotion speed (1.34-4.47 m·s -1 ). Tensiometry estimates of peak Achilles tendon force during running (8.2-10.1 body weights) were within the range of those estimated previously via indirect methods. CONCLUSIONS: These results set the stage for using tensiometry to evaluate Achilles tendon loading during unobstructed athletic movements, such as running, performed in the field.

Wearable sensing for understanding and influencing human movement in ecological contexts.

Wearable sensors offer a unique opportunity to study movement in ecological contexts - that is, outside the laboratory where movement happens in ordinary life. This article discusses the purpose, means, and impact of using wearable sensors to assess movement context, kinematics, and kinetics during locomotion, and how this information can be used to better understand and influence movement. We outline the types of information wearable sensors can gather and highlight recent developments in sensor technology, data analysis, and applications. We close with a vision for important future research and key questions the field will need to address to bring the potential benefits of wearable sensing to fruition.

Early Joint Use Following Elbow Dislocation Limits Range-of-Motion Loss and Tissue Pathology in Posttraumatic Joint Contracture.

BACKGROUND: Simple elbow dislocation occurs at an incidence of 2.9 to 5.21 dislocations per 100,000 person-years, with as many as 62% of these patients experiencing long-term elbow joint contracture, stiffness, and/or pain. Poor outcomes and the need for secondary surgical intervention can often be prevented nonoperatively with early or immediate active mobilization and physical therapy. However, immobilization or limited mobilization may be necessary following trauma, and it is unknown how different periods of immobilization affect pathological changes in elbow joint tissue and how these changes relate to range of motion (ROM). The purpose of this study was to investigate the effects of varying the initiation of free mobilization on elbow ROM and histological features in an animal model of elbow posttraumatic joint contracture. METHODS: Traumatic elbow dislocation was surgically induced unilaterally in rats. Injured forelimbs were immobilized in bandages for 3, 7, 14, or 21 days; free mobilization was then allowed until 42 days after injury. Post-mortem joint ROM testing and histological analysis were performed. One-way analysis of variance was used to compare ROM data between control and injured groups, and Pearson correlations were performed between ROM parameters and histological outcomes. RESULTS: Longer immobilization periods resulted in greater ROM reductions. The anterior and posterior capsule showed increases in cellularity, fibroblasts, adhesions, fibrosis, and thickness, whereas the measured outcomes in cartilage were mostly unaffected. All measured histological characteristics of the capsule were negatively correlated with ROM, indicating that higher degrees of pathology corresponded with less ROM. CONCLUSIONS: Longer immobilization periods resulted in greater ROM reductions, which correlated with worse histological outcomes in the capsule in an animal model of posttraumatic elbow contracture. The subtle differences in the timing of ROM and capsule tissue changes revealed in the present study provide new insight into the distinct timelines of biomechanical changes as well as regional tissue pathology. CLINICAL RELEVANCE: This study showed that beginning active mobilization 3 days after injury minimized posttraumatic joint contracture, thereby supporting an immediate-motion clinical treatment strategy (when possible). Furthermore, uninjured but pathologically altered periarticular tissues near the injury location may contribute to more severe contracture during longer immobilization periods as the disease state progresses.

Pleiotropic Effects of Simvastatin and Losartan in Preclinical Models of Post-Traumatic Elbow Contracture.

Elbow trauma can lead to post-traumatic joint contracture (PTJC), which is characterized by loss of motion associated with capsule/ligament fibrosis and cartilage damage. Unfortunately, current therapies are often unsuccessful or cause complications. This study aimed to determine the effects of prophylactically administered simvastatin (SV) and losartan (LS) in two preclinical models of elbow PTJC: an in vivo elbow-specific rat injury model and an in vitro collagen gel contraction assay. The in vivo elbow rat (n = 3-10/group) injury model evaluated the effects of orally administered SV and LS at two dosing strategies [i.e., low dose/high frequency/short duration (D1) vs. high dose/low frequency/long duration (D2)] on post-mortem elbow range of motion (via biomechanical testing) as well as capsule fibrosis and cartilage damage (via histopathology). The in vitro gel contraction assay coupled with live/dead staining (n = 3-19/group) evaluated the effects of SV and LS at various concentrations (i.e., 1, 10, 100 µM) and durations (i.e., continuous, short, or delayed) on the contractibility and viability of fibroblasts/myofibroblasts [i.e., NIH3T3 fibroblasts with endogenous transforming growth factor-beta 1 (TGFß1)]. In vivo, no drug strategy prevented elbow contracture biomechanically. Histologically, only SV-D2 modestly reduced capsule fibrosis but maintained elevated cellularity and tissue hypertrophy, and both SV strategies lessened cartilage damage. SV modest benefits were localized to the anterior region, not the posterior, of the joint. Neither LS strategy had meaningful benefits in capsule nor cartilage. In vitro, irrespective of the presence of TGFß1, SV (≥10 µM) prevented gel contraction partly by decreasing cell viability (100 µM). In contrast, LS did not prevent gel contraction or affect cell viability. This study demonstrates that SV, but not LS, might be suitable prophylactic drug therapy in two preclinical models of elbow PTJC. Results provide initial insight to guide future preclinical studies aimed at preventing or mitigating elbow PTJC.

Investigating the Effects of Physical Therapy Timing, Intensity and Duration on Post-Traumatic Joint Contracture in a Rat Elbow Model.

BACKGROUND: Post-traumatic joint contracture (PTJC), characterized by loss of motion and permanent stiffness, affects up to 50% of patients following elbow joint dislocation or fracture. Mechanisms governing successful conservative treatment methods aimed at preventing elbow PTJC and avoiding operative treatments (e.g., physical therapy) are poorly understood. Using a previously established rat model of elbow PTJC, the purpose of this study was to explore the effect of varying timing, intensity and duration of active, functional exercise on joint motion outcomes. METHODS: Following a surgically-induced unilateral elbow dislocation in rats, injured limbs were immobilized in bandages for 42 days followed by free mobilization for 42 additional days producing long-term PTJC. This work summarizes several studies (Phases I-III) that investigated the effects of early versus delayed therapy (timing), free mobilization versus forced treadmill walking (intensity), and limited-time versus unlimited use (duration) on elbow PTJC. RESULTS: Joint motion outcomes in therapy groups showed no improvements compared to non-treated injured animals when therapy began day 14 post-injury or later regardless of timing, intensity or duration. Improved joint range-of-motion was only achieved when bandages were permanently removed at day 3 post-injury, regardless of whether added treadmill walking was performed. CONCLUSION: Early motion is essential to preserving range-of-motion following traumatic elbow injury in a rat model.

Increased volume and collagen crosslinks drive soft tissue contribution to post-traumatic elbow contracture in an animal model.

Post-traumatic joint contracture (PTJC) in the elbow is a biological problem with functional consequences. Restoring elbow motion after injury is a complex challenge because contracture is a multi-tissue pathology. We previously developed an animal model of elbow PTJC using Long-Evans rats and showed that the capsule and ligaments/cartilage were the primary soft tissues that caused persistent joint motion loss. The objective of this study was to evaluate tissue-specific changes within the anterior capsule and lateral collateral ligament (LCL) that led to their contribution to elbow contracture. In our rat model of elbow PTJC, a unilateral surgery replicated damage that commonly occurs due to elbow dislocation. Following surgery, the injured limb was immobilized for 42 days. The capsule and LCL were evaluated after 42 days of immobilization or 42 days of immobilization followed by 42 days of free mobilization. We evaluated extracellular matrix protein biochemistry, non-enzymatic collagen crosslink content, tissue volume with contrast-enhanced micro-computed tomography, and tissue mechanical properties. Increased collagen content, but not collagen density, was observed in both injured limb capsules and LCLs, which was consistent with the increased tissue volume. Injured limb LCLs exhibited decreased normalized maximum force, and both tissues had increased immature collagen cross-links compared to control. Overall, increased tissue volume and immature collagen crosslinks in the capsule and LCL drive their contribution to elbow contracture in our rat model.

Females and males exhibit similar functional, mechanical, and morphological outcomes in a rat model of posttraumatic elbow contracture.

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.

The Open Source GAITOR Suite for Rodent Gait Analysis.

Locomotive changes are often associated with disease or injury, and these changes can be quantified through gait analysis. Gait analysis has been applied to preclinical studies, providing quantitative behavioural assessment with a reasonable clinical analogue. However, available gait analysis technology for small animals is somewhat limited. Furthermore, technological and analytical challenges can limit the effectiveness of preclinical gait analysis. The Gait Analysis Instrumentation and Technology Optimized for Rodents (GAITOR) Suite is designed to increase the accessibility of preclinical gait analysis to researchers, facilitating hardware and software customization for broad applications. Here, the GAITOR Suite's utility is demonstrated in 4 models: a monoiodoacetate (MIA) injection model of joint pain, a sciatic nerve injury model, an elbow joint contracture model, and a spinal cord injury model. The GAITOR Suite identified unique compensatory gait patterns in each model, demonstrating the software's utility for detecting gait changes in rodent models of highly disparate injuries and diseases. Robust gait analysis may improve preclinical model selection, disease sequelae assessment, and evaluation of potential therapeutics. Our group has provided the GAITOR Suite as an open resource to the research community at www.GAITOR.org , aiming to promote and improve the implementation of gait analysis in preclinical rodent models.