Sclerostin, a protein coded for by the SOST gene, is an osteocyte-expressed negative regulator of bone formation. The absence of SOST in the genome may have an effect on bone formation both during skeletal maturation and full maturity. This study attempts to determine significant differences in the mechanical properties of bone that expresses SOST compared to bone that does not. One hundred femur samples from 6, 8, and 12 month old mice were obtained from Lawrence Livermore National Labs and loaded until failure using three-point bending. Results showed significant differences in treatment group effects for cross sectional area, yield force, and ultimate force. SOST knockout (KO) mice were found to have significantly higher values for these properties in comparison to transgenic (TG) and wildtype (WT) littermates. In addition, there was a noted effect dependent on the primary axis of loading, anterior-posterior versus medial-lateral. Lastly, data from this study support the existing hypothesis that there is no systematic side-to-side (left-right) difference in bone formation. This data may aid understanding of the role SOST has in bone formation. If the structural integrity and quality of bone resulting from the removal of the SOST gene is shown to be comparable to that of normal, healthy bone, the use of gene therapy to combat diseases/disorders such as osteoporosis may lead to important contributions to medical therapy.

The ability to successfully switch hit, or hit a baseball from both sides of the plate, requires a great amount of practice and coordination bilaterally. This study used three-dimensional kinematic and kinetic data to examine the swing patterns of skilled switch hitters in baseball. Three male minor league and division I collegiate switch hitters participated. Subjects stood on force plates and hit baseballs off a tee while their swings were recorded with a three-dimensional optical motion capture system. Each subject performed twenty total swings, ten from the right and ten from the left. The swings were digitally analyzed and the dependent measures were compared side-to-side. The swing was broken down into specific events and temporal phase parameters were obtained. Peak vertical ground reaction force of each foot and stride length of each swing were also obtained. All variables were statistically analyzed using paired t-tests. The subjects displayed surface swing characteristics side-to-side that appeared identical and statistically there were no significant differences in the swing variables side-to-side. However, each subject had slight internal pattern differences side-to-side that are reported and discussed. Switch hitters are an excellent example of skilled practitioners that can provide insight into questions pertaining to dominance and motor control. Further research is needed with more subjects to explore side-to-side similarities and differences in well-established patterns.

Uterine motility is responsible for carrying out important processes throughout all phases of the female reproductive cycle, including sperm transport, menstruation, and embryo implantation. We present a model of intra-uterine fluid flow in a sagittal cross-section of the uterus by inducing peristalsis in a channel. The peristaltic waveform emerges from the coupling of cellular models to elastic walls and viscous fluid. This is an integrative multiscale spatial model that takes as input the fluid viscosity, passive uterine tissue properties, and a prescribed wave of membrane depolarization. Following Bursztyn et al. [1], the voltage pulse drives the calcium dynamics inside each smooth muscle cell along the uterine walls. This, in turn, drives the formation of cross-bridges in the cell which generate the contractile muscle forces. The forces predicted by this new model are coupled to the elastic channel walls and the viscous, incompressible fluid within the channel using an immersed boundary framework [2] The main contributions of this dissertation are two-fold. First, we present a modified Hai-Murphy model of uterine smooth muscle cell force generation that accounts for the displacement of myosin cross-bridge heads relative to their binding sites. Second, we couple this microscale model of force generation with an organ level model of the uterine channel that captures the elastic properties of the uterine walls and a viscous, incompressible fluid. We then examine how fluid transport is affected by changes on the molecular and cellular scales. In particular, we show how deficiencies in phosphorylation and calcium uptake affect intra-uterine fluid flow / acase@tulane.edu

BACKGROUND: Finite element models of lung motion can aid in understanding mechanically driven lung deformation. Current finite element models consider each lung half as a continuum, lacking the ability to capture the displacement discontinuity at fissures caused by lobe sliding. OBJECTIVE: The objective of this work was to develop and evaluate finite element models for simulating lung motion that incorporate the role of sliding at the lobe boundaries. METHODS: Finite element models were developed from 4DCT of tidal breathing from five cancer subjects. To allow sliding, the lobes were modeled as independent bodies within a pleural cavity shell. Pleural cavity deformation was obtained from deformable image registration of the lung segmentations. Contact between the pleural cavity and lobes prevented penetration and allowed sliding at all interfaces. Lung parenchyma was modeled as a homogeneous, 2-parameter, Neo-Hookean finite elastic model. The parameters of the Neo-Hookean model, C1 and D1, were optimized by perturbation within realistic reported ranges; defined by the equivalent infinitesimal elasticity parameters: Young's modulus (from 0.7 kPa to 70 kPa) and ν (from 0.2 to 0.49). The frictional coefficient at fissures was perturbed between 0 (free sliding) and 1.5 (no sliding). 1,960 finite element analyses were performed across the five subjects. The optimal parameter ranges were evaluated by average landmark error and percentage of converged solutions. The developed finite element method, using optimized material and friction parameters, was further evaluated in a data set of six healthy subjects with image pairs spanning functional residual capacity (FRC) to total lung capacity (TLC). The finite element predicted displacement field for lobe sliding finite element models and continuum-based finite element models were compared using average landmark error and correlation with the lobe-by-lobe deformable image registration results. RESULTS AND DISCUSSION: The optimal parameters for Young's modulus were 49 kPa to 70 kPa and Poisson's ratio were 0.2 to 0.4. Variation of inter-lobar frictional coefficients did change displacement field accuracy assessed by landmark error or correlation to lobe-by-lobe deformable image registration. Characteristics of sliding predicted by the lobe sliding finite element models were consistent with characteristics in sliding observed in deformable image registration results. Also, variations in regional ventilation, quantified at the lobe level, were predicted by the finite element models and were shown to be influenced by the amount of lobe sliding allowed by the models.

Disc degeneration is a natural process and is widely prevalent. The severity of disc degeneration and the type of treatment varies from person to person. Fusion is a commonly chosen treatment option. However, clinical and biomechanical studies have shown that intervertebral discs adjacent to a fusion experience increased motion and higher stress which may lead to adjacent-segment disease. Cervical disc arthroplasty achieves similar decompression of the neural elements, but preserves the motion at the operated level and may potentially decrease the occurrence of adjacent segment degeneration. Computationally, a validated intact 3D finite element model of the cervical spine (C2-T1) was modified to simulate single (C5-C6) and bi-level (C5-C7) degeneration. The single level degenerative model was modified to simulate single level fusion and arthroplasty with the Bryan and Prestige LP artificial discs. The bi-level degenerative model was modified to simulate a bi-level fusion, bi-level arthroplasty with Bryan and Prestige LP discs and a disc replacement adjacent to fusion. An in-vitro biomechanical study was also conducted to address the effects of arthroplasty and fusion on the kinematics of the cervical spine. A total of 11 specimens (C2-T1) were divided into two groups (Bryan and Prestige LP). The specimens were tested in the following order; intact, single level TDR at C5-C6, bi-level TDR C5-C6-C7, fusion at C5-C6 and TDR at C6-C7 (Hybrid construct) and finally a bi-level fusion. The intact state was tested up to a moment of 2Nm. After surgical intervention, the specimens were loaded until the primary motion (C2-T1) matched the motion of intact state (hybrid control). In all cases; computational and experimental, an arthroplasty preserved motion at the implanted level and maintained normal motion at the nonoperative levels. A fusion, on the other hand, resulted in a significant decrease in motion at the fused level and an increase in motion at the un-fused levels. In the hybrid construct, the TDR adjacent to fusion preserved motion at that level, thus reducing the demand on the other levels. The computational models were used to analyze disc stresses at the adjacent levels and facet forces at the index and adjacent levels. The disc stresses followed the same trends as motion. Facet forces though, increased considerably at the index level following a TDR. There was a decrease in facet forces however at the adjacent levels. The adjacent level facet forces increased considerably with a fusion. The hybrid construct had adjacent level facet forces between the bi-level TDR and bi-level fusion models. To conclude, this study highlighted that cervical disc replacement with both the Bryan and Prestige LP discs not only preserved the motion at the operated level, but also maintained the normal motion at the adjacent levels. Under hybrid loading, the motion pattern of the spine with a TDR was closer to the intact motion pattern, as compared to the degenerative or fusion models. Also, in the presence of a pre-existing fusion, this study shows that an adjacent segment disc replacement is preferable to a second fusion.

With over 7% (20 million) people in the United States affected by diabetes mellitus (DM), DM has emerged as a significant health problem. The hallmark of DM is multi-system involvement and the lower limbs are frequently involved in the form of foot ulcers. Inability to heal foot ulcers and maintain healing contributes to the high rate of amputation seen in individuals with DM. The development of foot ulcers has been strongly linked with mechanical stress. Changes in muscle characteristics and segmental foot mobility have been postulated to limit forward progression of the leg on the fixed foot during walking. This in turn may result in prolonged and excessive loading on the ball of the foot. However the extent and site of the impairments and their functional consequences are not well understood. The purpose of this work is to examine determinants of dynamic foot function and plantar loading in individuals with DM. Our results revealed that in spite of differences in passive ankle dorsiflexion and stiffness, subjects with DM demonstrated ankle motion, stiffness and plantar pressures, similar to control subjects, while walking at the identical speed, 0.89 m/s (2 mph). In terms of segmental mobility, reductions were particularly dramatic in the calcaneus (20%) compared to the forefoot and first metatarsal. Decreases in frontal plane calcaneal motion were accompanied by reduced midfoot mobility. Sagittal motion of the first metatarsal and forefoot, and frontal motion of the calcaneus, in subjects with DM, was negatively associated with the magnitude of plantar loading under the respective segment. This information is important because it may help elucidate underlying mechanisms and add to our understanding of the disease process and its effects. In addition, these results may help develop more focused intervention strategies.

Osteoarthritis is a chronic, deleterious disease of the joints. It currently affects nearly 25 million Americans. Clinically, osteoarthritis presents as joint pain and verified by radiographic evidence of joint space narrowing. Unfortunately, symptomatic osteoarthritis describes the later stages of disease, at which point irreversible cartilage and bone damage has occurred. Cross-sectional imaging modalities offer the promise of visualizing early features of disease, enabling the development and evaluation of interventions to forestall or prevent degenerative change. Modalities of clinical interest include magnetic resonance imaging (MRI) and multi-detector computed tomography (MDCT). The following work describes the efficacy of MRI-derived measures for the identification and accurate quantification of local and whole joint changes in articular cartilage thickness changes in vivo. This was performed as part of a study investigating the diagnostic potential of clinical morphometric and compositional MRI to identify early features of osteoarthritis in a large animal model of traumatic knee joint injury. Surgically induced trauma consisted of a partial medial meniscectomy and blunt impact of either 0 J, 0.6 J, or 1.2 J to the weight-bearing cartilage of the medial femur. The study was six months in duration. To evaluate the accuracy of MRI-derived measures of cartilage thickness, imaging acquired at time of euthanasia was compared to high-resolution contrast-enhanced micro-computed tomography (micro CT). 3-dimensional multimodal analysis demonstrated that morphometric MRI imaging is sensitive to sub-voxel changes in cartilage thickness. Therefore, MRI is a clinically relevant modality to quantify subtle cartilage damage, thereby presenting an opportunity to identify patients earlier in the disease process.

The purpose of this study was to assess the acute effects of static stretching on foot velocity at impact with a soccer ball. Eighteen Division I female soccer athletes underwent two test conditions separated by 48 hr. Each condition was randomly assigned and began by placing four retro-reflective markers on bony landmarks of the ankle (total of eight markers, four on each ankle). One condition was the no-stretch condition, in which each participant performed a self-paced jog for 5 min as a warm-up, and then sat quietly for 6 min before performing three maximal instep kicks into a net. The second condition was the stretch condition, which was identical to the no-stretch condition, except the participants performed a series of six randomly ordered stretches instead of sitting quietly for 6 min. Three-dimensional motion analysis was used to quantify the resultant velocity of the head of the 5th metatarsal immediately prior to foot impact with a soccer ball. The results of a dependent t test indicated that there was no significant difference between the no-stretch (18.34 ± 1.29 m/s) and stretch conditions (17.96 ± 1.55 m/s; p = .102, d = .3) Based on these findings, acute stretching performed one time for 30 s before maximal instep soccer kicking has no effect on the resultant foot velocity of Division 1A university female soccer players. Pre-event stretching performed in a like manner may best be prescribed at the discretion of the athlete.

80% of the American population experiences back pain and it is the most common cause of limited activity in people of age 45 and under. Determining the reasons for back pain and developing new ways to treat it have been extensively researched over the past decade. However, very little research has been done on low back pain of amputees. There are four million existing amputees living in America and 250,000 people become new amputees each year. 70% of this group is lower limb amputees and a large number use a prosthesis of some kind to aid in the functions of daily living (Amputation and Limb Deficiency). Not all amputees use a prosthesis because of pain involved, aesthetics, and cost. In order to increase the use of prosthetics among amputees, the reasons why they do not use them must be fully understood. With this knowledge better prosthetic designs can be created. The purpose of this study is to first determine the prevalence of back pain among lower limb amputees who use a prosthesis and then to quantify the accelerations in the spine of this group and compare it to subjects who are not amputees. The findings of this study will be used to determine if back pain is a common complaint, if it interferes with daily activities, and if the use of a prosthesis causes abnormal loads in the spine of amputees. A cross-sectional descriptive survey was created and distributed to lower limb amputees who use a prosthesis and to a control group. In addition to the survey, several subjects were recruited to wear an accelerometer located over the L5-S1 vertebrae and walk at several speeds down a pathway. A maximum acceleration was determined for each step as well as the difference in acceleration between opposing legs. Also measured was the effect of a leg length discrepancy (LLD) on accelerations and back pain. As a result of this research it was found that a high percentage of amputees experience back pain and the prevalence is higher than that of controls. It has shown that there is a difference between the acceleration patterns of amputees and non-amputees, but further research is needed to show that this difference is what causes the higher prevalence of back pain. The trend of side dominance and its increase with increased walking speed for amputees has been shown as well as a general population trend of increased acceleration of the spine with increased speed. In relation to walking speed, the study has also shown that the perception of speed among amputees is slower than that of controls. This study has also supported the notion that a difference in leg length could cause low back pain.

Estudos demonstram que um toque efetuado pela ponta do dedo indicador sobre uma superfície externa rígida (a força exercida é mínima, não configurando um apoio mecânico) diminui consideravelmente a oscilação postural, o que indica que as informações sensoriais adquiridas pelos receptores táteis da ponta do dedo (i.e. relacionadas com as forças de contato entre o dedo e a superfície de apoio) fornecem ao sistema nervoso central informações relevantes que ajudam a manter a estabilidade postural. Esse efeito estabilizador proveniente do toque também tem sido associado a mecanismos supraposturais, como requisitos de precisão manual e demandas de atenção. A demanda atencional investida durante uma dada tarefa postural tem sido associada à regularidade das oscilações posturais, estimada pela entropia da amostra (SaEn) dos sinais do centro de pressão (CoP) (SaEnCoP). No entanto, nenhuma investigação anterior abordou se a regularidade das trajetórias do CoP é influenciada pelo toque suave do dedo (em inglês light touch LT) durante as tarefas posturais. Com base nos achados de estudos anteriores que sugeriram aumento da demanda atencional associada ao toque suave dos dedos (em comparação às condições de controle sem toque), a hipótese abordada foi de que a realização de tarefas posturais ao tocar levemente uma superfície externa rígida, além de atenuar a magnitude das oscilações posturais, estaria associada a níveis mais altos de regularidade do CoP (isto é, medidas baixas do SaEnCoP) em comparação com as condições de controle sem toque. Neste sentido, o objetivo do presente projeto foi investigar o efeito do toque suave do dedo sobre a regularidade das flutuações do CoP durante a manutenção da postura quieta bipedal e em uma tarefa de equilíbrio unipedal, de modo a analisar duas tarefas de controle postural com diferentes níveis de complexidade, associadas a diferentes níveis de demanda atencional. Sendo assim, 8 voluntários participaram dos experimentos na tarefa em postura quieta bipedal e 14 na tarefa de equilíbrio unipedal, ambas com e sem informação tátil adicional. Foram obtidos maiores valores de SaEnCoP na condição LT, tanto na tarefa de postura bipedal quanto em unipedal, sendo as diferenças significativas em relação a condição NT. Os resultados indicam que a presença de informações táteis adicionais levou a redução da instabilidade postural, mas não aumentou o grau de demanda de atenção na postura pelas flutuações do CoP mais irregulares (maiores valores de SaEnCoP), mesmo na tarefa mais complexa (equilíbrio unipedal). Isso sugere que, a automaticidade do controle postural foi maior, o que significa que a presença do toque tornou o controle postural mais efetivo (reduzindo as oscilações posturais), mas não o tornou mais cognitivamente dependente / Studies have been demonstrated that lightly touching an external rigid (the force exerted is minimal not setting a mechanical support) surface reduce the magnitude of postural oscillation. This decrease of postural sway indicates that the sensory information acquired by fingertip tactile receptors provides the central nervous system relevant information that aid to maintain postural stability. The stabilizing effect of light finger touch has been associated with sensory mechanisms involving enhanced proprioceptive feedback (e.g., from finger and hand muscles as well as from joint and cutaneous mechanoreceptors) and also with suprapostural mechanisms such as manual precision requirements and attentional demand. The attentional demand invested during a postural task has been associated with the regularity of the postural oscillations, as estimated by the sample entropy (SaEn) of center of pressure (CoP) signals (SaEnCoP). However, no previous investigation has addressed whether the regularity of CoP trajectories is influenced by light finger touch during postural tasks. Based on the previous findings that suggested an increased attentional demand associated with light finger touch (as compared to control conditions with no touch), the hypothesis addressed in the present study was that postural tasks performed when lightly touching an external rigid surface, besides attenuating the magnitude of postural oscillations, would be associated with higher levels of CoP regularity (i.e. lower measurements of SaEnCoP) as compared to control conditions with no touch. Therefore, the aim of this study was to investigate the effect of light finger touch on CoP regularity during two postural control tasks, quiet bipedal and single leg stance to investigate postural control tasks with different levels of complexity, which has been associated with different levels of attentional demand. We evaluated the CoP fluctuations in 8 volunteers during quiet bipedal posture and in 14 volunteers during single leg postural task, both with and without light finger touch. We obtained greater values os SaEnCoP in the LT condition in both bipedal and single leg posture tasks with significant differents compared to the NT condition. The findings indicate that light finger touch producing additional tactile informations that reduced postural instability did not increase the degree of attention demand in posture with the more irregular CoP fluctuations, even in the more complex task (single-leg stance). This suggests that the automaticity of postural control was greater which means that the presence of touch made postural control more effective (reducing postural oscillations), but did not made it more cognitively dependent