Investigation of index finger triggering force using a cadaver experiment: Effects of trigger grip span, contact location, and internal tendon force.

A cadaver study was conducted to investigate the effects of triggering conditions (trigger grip span, contact location, and internal tendon force) on index finger triggering force and the force efficiency of involved tendons. Eight right human cadaveric hands were employed, and a motion simulator was built to secure and control the specimens. Index finger triggering forces were investigated as a function of different internal tendon forces (flexor digitorum profundus + flexor digitorum superficialis = 40, 70, and 100 N), trigger grip spans (40, 50, and 60 mm), and contact locations between the index finger and a trigger.

Femoral fixation strength following soft-tissue posterolateral corner reconstruction using fibular-based technique: Biomechanical analysis of four techniques in normal and low-density synthetic bone.

Background: Optimal femoral fixation of soft-tissue grafts has been described for anterior cruciate ligament reconstruction. Posterolateral corner reconstruction differs from ACL reconstruction in two ways: (a) soft-tissue fixation into the femur requires two tails and (b) the line of force is different. Our purpose was to determine the optimal femoral fixation of soft-tissue grafts during posterolateral corner reconstructions.

Segmental motion of forefoot and hindfoot as a diagnostic tool.

Segmental motions derived from non-invasive motion analysis are being used to investigate the intrinsic functional behavior of the foot and ankle in health and disease. The goal of this research was to examine the ability of a generic segmented model of the foot to capture and differentiate changes in internal skeletal kinematics due to neuromuscular disease and/or trauma. A robotic apparatus that reproduces the kinematics and kinetics of gait in cadaver lower extremities was employed to produce motion under normal and aberrant neuromuscular activation patterns of tibialis posterior and/or tibialis anterior.

Midtarsal joint locking: new perspectives on an old paradigm.

We investigated the existence of a midtarsal joint locking mechanism using cadaveric simulations of normal gait. Previous descriptions of this phenomenon led us to hypothesize that non-coupled rotations of the calcaneocuboid and talonavicular (i.e.

Experimental evidence supporting isometric functioning of the extrinsic toe flexors during gait.

Background: The extrinsic toe flexors, flexor hallucis longus and flexor digitorum longus, play an important role in stabilizing the longitudinal arch and supporting high forefoot loads during the stance phase of gait. It was hypothesized that these muscles function isometrically during stance, a strategy thought to provide efficient energy transfer across adjoining body segments, but one for which there is little direct experimental evidence in vivo or in situ.

Methods: Eight lower extremity cadavers were loaded into a robotic apparatus that simulates the kinematics and extrinsic muscle activity of the foot and distal tibia during the stance phase of gait.

Partial sleep deprivation and energy balance in adults: an emerging issue for consideration by dietetics practitioners.

During the past 30 years, rates of partial sleep deprivation and obesity have increased in the United States. Evidence linking partial sleep deprivation, defined as sleeping <6 hours per night, to energy imbalance is relevant to weight gain prevention and weight loss promotion. With a majority of Americans overweight or obese, weight loss is a recommended strategy for reducing comorbid conditions.

Enhanced osteoclastic resorption and responsiveness to mechanical load in gap junction deficient bone.

Emerging evidence suggests that connexin mediated gap junctional intercellular communication contributes to many aspects of bone biology including bone development, maintenance of bone homeostasis and responsiveness of bone cells to diverse extracellular signals. Deletion of connexin 43, the predominant gap junction protein in bone, is embryonic lethal making it challenging to examine the role of connexin 43 in bone in vivo. However, transgenic murine models in which only osteocytes and osteoblasts are deficient in connexin 43, and which are fully viable, have recently been developed.

Mechanical characteristics of a novel posterior-step prosthesis for biconcave glenoid defects.

Background: Posterior glenoid defects increase the risk of glenoid component loosening after total shoulder arthroplasty (TSA). The goal of this work was to evaluate the mechanical performance of a novel posterior-step glenoid prosthesis, designed to compensate for biconcave (type B2) glenoid defects. Two prototypes ("Poly-step" and "Ti-step") were constructed by attaching polyethylene or titanium step-blocks onto standard (STD) glenoid prostheses.

A biomechanical study of posterior glenoid bone loss and humeral head translation.

Background: Results of shoulder arthroplasty have been reported to be inferior with posterior glenoid wear and accompanying subluxation of the humeral head. The purpose of this study was to examine the effect of posterior glenoid wear on posterior subluxation of the humeral head.

Material And Methods: A custom loading device was used to simulate physiologic loading conditions in 8 cadaver shoulders with the humerus positioned at neutral, forward flexion, and extension.

Localization of osteoblast inflammatory cytokines MCP-1 and VEGF to the matrix of the trabecula of the femur, a target area for metastatic breast cancer cell colonization.

Bone likely provides a hospitable environment for cancer cells as suggested by their preferential localization to the skeleton. Previous work has shown that osteoblast-derived cytokines increased in the presence of metastatic breast cancer cells. Thus, we hypothesized that osteoblast-derived cytokines, in particular IL-6, MCP-1, and VEGF, would be localized to the bone metaphyses, an area to which breast cancer cells preferentially traffic.

Biomimetic bone mechanotransduction modeling in neonatal rat femur organ cultures: structural verification of proof of concept.

The goal of this work was to develop and validate a whole bone organ culture model to be utilized in biomimetic mechanotransduction research. Femurs harvested from 2-day-old neonatal rat pups were maintained in culture for 1 week post-harvest and assessed for growth and viability. For stimulation studies, femurs were physiologically stimulated for 350 cycles 24 h post-harvest then maintained in culture for 1 week at which time structural tests were conducted.

Reliability and validity of a novel muscle contusion device.

Context: Many models have been employed to replicate skeletal muscle injury associated with trauma; however, most are restricted to 1 level of severity.

Objective: To create and validate an injury-producing device that could generate multiple levels of injury severity.

Design: Validation study.

Bone, muscle, and physical activity: structural equation modeling of relationships and genetic influence with age.

Correlations among bone strength, muscle mass, and physical activity suggest that these traits may be modulated by each other and/or by common genetic and/or environmental mechanisms. This study used structural equation modeling (SEM) to explore the extent to which select genetic loci manifest their pleiotropic effects through functional adaptations commonly referred to as Wolff's law. Quantitative trait locus (QTL) analysis was used to identify regions of chromosomes that simultaneously influenced skeletal mechanics, muscle mass, and/or activity-related behaviors in young and aged B6xD2 second-generation (F(2)) mice of both sexes.

Changes in postural sway as a consequence of wearing a military backpack.

Military personnel are often required to carry all of their personal supplies and equipment for long distances during both training and combat situations, creating many biomechanical and postural challenges for these individuals. In addition to other problems such as generalized fatigue and the development of stress fractures, significant external loads may also affect a soldier's postural sway. The purpose of this study was to assess changes in postural sway as a consequence of wearing a military backpack in females.

Magnetic resonance imaging of acute injury in rats and the effects of buprenorphine on limb volume.

The purposes of this study were to determine 1) whether magnetic resonance imaging (MRI)-based T2 mapping and measurements of limb volume can differentiate injured and uninjured tissue after blunt trauma to rat hindlimbs and 2) whether administration of buprenorphine influences these assessments. Male Wistar rats (age, 3 to 4 mo) underwent blunt contusion injury to the posterior aspect of the hindlimb; MRI was conducted at 6, 12, 24, 48, 72, and 96 h after injury. The imaging results showed that administration of buprenorphine had no effect on the T2 value {area under the receiver operating characteristic [ROC] curve: with drug, 0.

An objective evaluation of a segmented foot model.

Segmented foot and ankle models divide the foot into multiple segments in order to obtain more meaningful information about its functional behavior in health and disease. The goal of this research was to objectively evaluate the fidelity of a generalized three-segment foot and ankle model defined using externally mounted markers. An established apparatus that reproduces the kinematics and kinetics of gait in cadaver lower extremities was used to independently examine the validity of the rigid body assumption and the magnitude of soft tissue artifact induced by skin-mounted markers.

Contribution of the flexor hallucis longus to loading of the first metatarsal and first metatarsophalangeal joint.

Background: A recent clinical study suggested that restrictive tenosynovitis of the flexor hallucis longus (FHL) may play an important causative role in hallux rigidus. The goals of this research were to assess normal function of the FHL and the effect of restricted FHL gliding on the loading of the hallux metatarsophalangeal joint (MTPJ). We hypothesized that proximal displacement of the FHL would increase the forces carried by the FHL tendon, causing increased loading of the first metatarsal and MTPJ.

Genes in context: probing the genetics of fracture resistance.

Fracture resistance is a complex trait dictated by bone volume, shape, internal architecture, and material performance of the calcified tissue itself, all of which may be influenced by a large number of different genetic and environmental processes. Quantitative Trait Loci analyses provide a sobering picture of this system and illustrate the importance of considering genes in context.

Effects of strontium on bone strength, density, volume, and microarchitecture in laying hens.

Unlabelled: Strontium has been reported to have beneficial effects on bone. Treatment of laying hens, which are susceptible to osteoporosis and bone fracture, with strontium increased DXA measurements of BMD and BMC and microCT measurements of bone volume and microarchitecture and improved the mechanical performance of whole bone, but had no effect on the estimated material properties of the bone tissue.

Introduction: Strontium (Sr) has been reported to dissociate bone remodeling and have positive influences on bone formation.

QTL analysis of trabecular bone in BXD F2 and RI mice.

Unlabelled: A sample of 693 mice was used to identify regions of the mouse genome associated with trabecular bone architecture as measured using microCT. QTLs for bone in the proximal tibial metaphysis were identified on several chromosomes indicating regions containing genes that regulate properties of trabecular bone.

Introduction: Age-related osteoporosis is a condition of major concern because of the morbidity and mortality associated with osteoporotic fractures in humans.

Adjusting data to body size: a comparison of methods as applied to quantitative trait loci analysis of musculoskeletal phenotypes.

Unlabelled: The aim of this study was to compare three methods of adjusting skeletal data for body size and examine their use in QTL analyses. It was found that dividing skeletal phenotypes by body mass index induced erroneous QTL results. The preferred method of body size adjustment was multiple regression.

Quantitative trait loci analysis of structural and material skeletal phenotypes in C57BL/6J and DBA/2 second-generation and recombinant inbred mice.

Unlabelled: QTL analyses identified several chromosomal regions influencing skeletal phenotypes of the femur and tibia in BXD F2 and BXD RI populations of mice. QTLs for skeletal traits co-located with each other and with correlated traits such as body weight and length, adipose mass, and serum alkaline phosphatase.

Introduction: Past research has shown substantial genetic influence on bone quality, and the impact of reduced bone mass on our aging population has heightened the interest in skeletal genetic research.

The effect of ankle injury on subtalar motion.

Background: Injuries to the medial and lateral ankle ligaments have been implicated in subtalar joint instability. Lateral injury increased subtalar joint varus and anterior translation, while deltoid injury increased external rotation and valgus in studies using static, non-physiologic testing.

Methods: The current study employed a physiologically accurate ankle model using phasic force-couples attached to the muscle-tendon units to reproduce ankle motion.

Relative motions of the tibia, talus, and calcaneus during the stance phase of gait: a cadaver study.

The motions of the tibia, talus, and calcaneus during walking were analyzed three-dimensionally using a dynamic cadaver model that recreates the stance phase of walking. Rigid marker clusters were attached to each of the three bones, and the rotations of the talus and calcaneus with respect to the tibia and the calcaneus with respect to the talus were analyzed for eight right cadaver feet. The talus rotated primarily in plantarflexion/dorsiflexion about the talocrural joint, with an average range of 18 degrees +/- 4.