Blocking CCN2 Reduces Established Bone Loss Induced by Prolonged Intense Loading by Increasing Osteoblast Activity in Rats.

We have an operant model of reaching and grasping in which detrimental bone remodeling is observed rather than beneficial adaptation when rats perform a high-repetition, high-force (HRHF) task long term. Here, adult female Sprague-Dawley rats performed an intense HRHF task for 18 weeks, which we have shown induces radial trabecular bone osteopenia. One cohort was euthanized at this point (to assay the bone changes post task; HRHF-Untreated).

Manual Therapy Facilitates Homeostatic Adaptation to Bone Microstructural Declines Induced by a Rat Model of Repetitive Forceful Task.

The effectiveness of manual therapy in reducing the catabolic effects of performing repetitive intensive force tasks on bones has not been reported. We examined if manual therapy could reduce radial bone microstructural declines in adult female Sprague-Dawley rats performing a 12-week high-repetition and high-force task, with or without simultaneous manual therapy to forelimbs. Additional rats were provided 6 weeks of rest after task cessation, with or without manual therapy.

Blocking CCN2 Reduces Progression of Sensorimotor Declines and Fibrosis in a Rat Model of Chronic Repetitive Overuse.

Fibrosis may be a key factor in sensorimotor dysfunction in patients with chronic overuse-induced musculoskeletal disorders. Using a clinically relevant rodent model, in which performance of a high demand handle-pulling task induces tissue fibrosis and sensorimotor declines, we pharmacologically blocked cellular communication network factor 2 (CCN2; connective tissue growth factor) with the goal of reducing the progression of these changes. Young adult, female Sprague-Dawley rats were shaped to learn to pull at high force levels (10 min/day, 5 weeks), before performing a high repetition high force (HRHF) task for 3 weeks (2 h/day, 3 days/week).

Prolonged high force high repetition pulling induces osteocyte apoptosis and trabecular bone loss in distal radius, while low force high repetition pulling induces bone anabolism.

We have an operant rat model of upper extremity reaching and grasping in which we examined the impact of performing a high force high repetition (High-ForceHR) versus a low force low repetition (Low-ForceHR) task for 18weeks on the radius and ulna, compared to age-matched controls. High-ForceHR rats performed at 4 reaches/min and 50% of their maximum voluntary pulling force for 2h/day, 3days/week. Low-ForceHR rats performed at 6% maximum voluntary pulling force.

Mechanical behavior of porcine thoracic aorta in physiological and supra-physiological intraluminal pressures.

Understanding the mechanical behavior of aorta under supra-physiological loadings is an important aspect of modeling tissue behavior in various applications that involve large deformations. Utilizing inflation-extension experiments, the mechanical behavior of porcine descending thoracic aortic segments under physiological and supra-physiological intraluminal pressures was investigated. The pressure was changed in the range of 0-70 kPa and the deformation of the segment was determined in three dimensions using a custom-made motion capture system.

Frequent mild head injury promotes trigeminal sensitivity concomitant with microglial proliferation, astrocytosis, and increased neuropeptide levels in the trigeminal pain system.

Background: Frequent mild head injuries or concussion along with the presence of headache may contribute to the persistence of concussion symptoms.

Methods: In this study, the acute effects of recovery between mild head injuries and the frequency of injuries on a headache behavior, trigeminal allodynia, was assessed using von Frey testing up to one week after injury, while histopathological changes in the trigeminal pain pathway were evaluated using western blot, ELISA and immunohistochemistry.  RESULTS: A decreased recovery time combined with an increased mild closed head injury (CHI) frequency results in reduced trigeminal allodynia thresholds compared to controls.

Investigation of inhomogeneous and anisotropic material behavior of porcine thoracic aorta using nano-indentation tests.

This study investigates the inhomogeneity and anisotropy of porcine descending thoracic aorta in three dimensions using a custom-made nano-indentation technique and a quasi-linear viscoelastic modeling approach. The indentation tests were conducted in axial, circumferential, and radial orientations with about 100 μm spatial resolution. The ratio of the elastic moduli obtained in different orientations was used to quantify the tissue local anisotropy.

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence.

Importance: An increased understanding of the relationship between subconcussive head impacts and near point of convergence (NPC) ocular-motor function may be useful in delineating traumatic brain injury.

Objective: To investigate whether repetitive subconcussive head impacts during preseason football practice cause changes in NPC.

Design, Setting, And Participants: This prospective, observational study of 29 National Collegiate Athletic Association Division I football players included baseline and preseason practices (1 noncontact and 4 contact), and postseason follow-up and outcome measures were obtained for each time.

Correlations between transmural mechanical and morphological properties in porcine thoracic descending aorta.

Determination of correlations between transmural mechanical and morphological properties of aorta would provide a quantitative baseline for assessment of preventive and therapeutic strategies for aortic injuries and diseases. A multimodal and multidisciplinary approach was adopted to characterize the transmural morphological properties of descending porcine aorta. Histology and multi-photon microscopy were used for describing the media layer micro-architecture in the circumferential-radial plane, and Fourier Transform infrared imaging spectroscopy was utilized for determining structural protein, and total protein content.

Computational simulation of the mechanical response of brain tissue under blast loading.

In the present study, numerical simulations of nonlinear wave propagation and shock formation in brain tissue have been presented and a new mechanism of injury for blast-induced neurotrauma (BINT) is proposed. A quasilinear viscoelastic (QLV) constitutive material model was used that encompasses the nonlinearity as well as the rate dependence of the tissue relevant to BINT modeling. A one-dimensional model was implemented using the discontinuous Galerkin finite element method and studied with displacement- and pressure-input boundary conditions.

Biomechanical comparison of locked plating and spiral blade retrograde nailing of supracondylar femur fractures.

Objective: Biomechanical comparison between locked plating and retrograde nailing of supracondylar femur fractures with simulated postoperative weight-bearing.

Methods: The Locking Condylar Plate (LCP) and Retrograde/Antegrade EX Femoral Nail (RAFN) were tested using 10 paired elderly cadaveric femurs, divided into Normal and Low Bone Mineral Density (BMD) groups, with a simulated AO/OTA type 33-A3 supracondylar femur fracture. Each specimen was subjected to 200,000 loading cycles in an attempt to simulate six weeks of postoperative recovery with full weight-bearing for an average individual.

Biomechanical analysis of second-generation headless compression screws.

Introduction: Headless Compression Screws (HCS) are commonly utilized for the fixation of small bone and articular fractures. Recently several new second generation HCS (SG-HCS) have been introduced with the purported benefits of improved biomechanical characteristics. We sought to determine and compare the biomechanical efficiencies of these screws.