Changes in the Standing Lumbar Spine at Above Bodyweight Loading

Introduction and Objectives: Understanding the mechanical response of the spine and intervertebral disc to various loading situations is vital to predicting its behaviour, to verify computer models of the spine and to gaining insight in to how loading and spinal posture may cause or exacerbate injury. Studies of the lumbar spine and intervertebral disc under compression have typically been carried out in vitro; those which have used in vivo methods have mostly been conducted in the supine position at loading equal to or below static bodyweight. This study measures the lumbar spine response to above bodyweight loading in the standing position at loads equivalent to walking. Methods: Sagittal plane magnetic resonance imaging scans of the spine were taken of nine asymptomatic male subjects (22-32 years of age, 167-195 cm, 66.3-93.2 kg) in the supine and standing positions with a third scan taken in the standing position with additional loading. Additional load was applied by having subjects hold two 6 kg kettlebells, one in each hand, enough to increase loading on the IVD to levels experienced during walking. Disc heights were measured as the average of anterior and posterior distance between adjacent vertebrae in the midsagittal plane. Change in lordosis was measured in two ways; the relative angle between the lumbar spine and pelvis was measured as the posterior angle between L5 and S1 vertebrae whilst change in the upper lumbar spine was measured by the angle between the superior facet of L3 with the vertical plane. Results: Increased axial loading resulted in reduced disc height and lumbar lordosis. Initial disc heights in the supine position for L3/L4, L4/L5 and L5/S1 were found to be 10.7(1.6), 12.0(2.8) and 11.4(1.9) mm respectively (Fig. 1a). These heights were reduced to 10.4(1.9), 11.4(2.1) and 10.8(1.6) mm in the standing position and 10.3(1.4), 11.4(2.0) and 10.4(1.8) mm with additional loading but these changes were not statistically significant (P>0.05). Lumbar angle in supine, standing and with additional loading was found to be 140(9), 145(11) and 145(12) degrees respectively (Fig. 1b) with L3 angled 0.7 (3.5), 4.4 (4.4) and 4.8 (4.2) degrees posteriorly from the horizontal in the three loading positions (Fig. 1c). In all cases disc height change was greater posteriorly as loading increased lumbar lordosis

Experimental Modelling of Viscoelastic Self-Heating in Healthy and Degenerate Bovine Intervertebral Discs

Objectives Low back pain (LBP) is an increasing drain on developed economies due to direct medical costs and lost working days. The majority of medical costs can be attributed to long-term problems resulting from specific physiological conditions. Acute injury and/or chronic degeneration of the intervertebral disc (IVD) has been linked with long term pain with high levels of nerve in-growth in degenerate IVDs. The fact that disc degeneration is a structural failing and not just a pathogenesis of pain may lead to reduced mobility and quality of life (QOL). Degenerate IVDs have elevated levels of heat shock proteins (HSPs) and HSPs elevated temperatures and/or heat shock within the IVD is a potential mechanism for HSP upregulation. Is it possible that high temperatures are a precursor to degeneration? Could activities of daily living (ADL) result in elevated temperatures in the IVD? This study aims to determine if there is a significant generation of heat within the IVD when subjected to cyclic loading at levels and frequencies relevant to ADL and whether this is effected by degeneration. Materials and Methods Bovine coccygeal discs were removed whole from tail sections and half of the discs were injected with a 2mg/ml collagenase solution and incubated at 37°C for 2 hours to simulate moderate degeneration. Discs were then subjected to sinusoidal loading at 2Hz at force levels equivalent to those in the human spine during locomotion. Mechanical data was analysed with MATLAB software to determine the energy dissipated by the discs for each cycle of loading and an idealised thermal model was generated to predict temperature change within the disc. Results Under axial loading equivalent to that in the lumbar spine during walking degenerate discs showed greater average compression than healthy discs (0.108mm and 0.024mm respectively) and therefore substantially lower average stiffness (714N/mm and 3149N/mm). Average heat generation in degenerate IVDs (2.79mW) was lower than that in healthy discs (4.13mW). An idealised 3D model of heat loss from the disc showed no significant increase in disc temperature in either healthy or degenerate disc condition. Conclusions Heat generated due to dissipated energy from axial loading of intervertebral discs at loading equivalent to that in the lumbar spine when walking is not enough to induce significant temperature increases within the disc. If elevated levels of HSPs within degenerate discs are the result of high temperatures, heat generated within the disc due to activities of daily living such as walking are not the cause

Material Behaviours of Healthy, Degenerate and Hydrogel Injected Bovine Intervertebral Discs

Objectives Low back pain (LBP) is an increasing drain on developed economies due to direct medical costs and lost working days. The majority of medical costs can be attributed to long-term problems resulting from specific physiological conditions. Acute injury and/or chronic degeneration of the intervertebral disc (IVD) has been linked with long term pain with high levels of nerve in-growth in degenerate IVDs. The fact that disc degeneration is a structural failing and not just a pathogenesis of pain may lead to reduced mobility and quality of life (QOL). Mesenchymal stem cell (MSC) interventions have been proposed as a treatment for degenerate IVDs but little is known about how the injection of a hydrogel matrix required by such interventions affects the material properties of the intervertebral disc and what effects this might have on disc health. This study aims to determine the difference in material behaviours of healthy, degenerate and hydrogel injected IVDs subjected to cyclic loading simulating activities of daily living (ADL). Materials and Methods Bovine coccygeal discs were dissected whole from tail sections and split in to three equal test groups; healthy, degenerate and hydrogel injected. Degenerate and hydrogel injected groups were injected with a 2 mg/ml collagenase solution and incubated at 37°C for 2 hours to simulate moderate degeneration, the hydrogel injected group then received a hydrogel injection. All discs were then subjected to sinusoidal loading at 2Hz at force levels equivalent to those in the human spine during walking and mechanical data analysed to determine respective material behaviours of each group. Results Under axial loading simulating walking in the lumbar spine compression (absolute and relative strain) and stiffness of discs varied across all three test groups. Conclusions Cyclic loading simulating activities of daily living was found to result in different material behaviours in bovine intervertebral discs that were moderately degenerated and/or injected with hydrogel relative to healthy discs

Lime stabilisation for earthworks: a UK perspective

Lime stabilisation is a versatile technique applied during earthworks operations. Modern soil recycling units are much more efficient at pulverising fill material and intermixing the added binder/water than machinery available 20 years ago. While supplier innovation adds flexibility to the site working method, specifications have not been sufficiently updated to permit optimal application. This review paper details the physico-chemical changes instigated through the lime-clay soil reaction, updating previous reviews. It aims to assist scientific debate, current practitioners and future specification changes. For example, the application of the minimum 24 h mellowing periods (mandatory to UK specifications) with high reactivity, quicklime powders is concluded to cause increased air voids in the compacted fill. Increased air voids are associated with reduced long-term strength and potential volume change from water ingress, which is of particular concern for sulfate swelling. Shorter mellowing periods and/or use of hydrated lime may lesson this issue; however, a 'one size fits all' approach is discouraged in preference to site-specific methodologies refined to suit the fill material and project requirements. The discussion also summarises working methods which may lower the risk of sulfate swell and defines areas requiring further practical research

Whole home exercise intervention for depression in older care home residents (the OPERA study) : a process evaluation

Background: The ‘Older People’s Exercise intervention in Residential and nursing Accommodation’ (OPERA) cluster randomised trial evaluated the impact of training for care home staff together with twice-weekly, physiotherapist-led exercise classes on depressive symptoms in care home residents, but found no effect. We report a process evaluation exploring potential explanations for the lack of effect. Methods: The OPERA trial included over 1,000 residents in 78 care homes in the UK. We used a mixed methods approach including quantitative data collected from all homes. In eight case study homes, we carried out repeated periods of observation and interviews with residents, care staff and managers. At the end of the intervention, we held focus groups with OPERA research staff. We reported our first findings before the trial outcome was known. Results: Homes showed large variations in activity at baseline and throughout the trial. Overall attendance rate at the group exercise sessions was low (50%). We considered two issues that might explain the negative outcome: whether the intervention changed the culture of the homes, and whether the residents engaged with the intervention. We found low levels of staff training, few home champions for the intervention and a culture that prioritised protecting residents from harm over encouraging activity. The trial team delivered 3,191 exercise groups but only 36% of participants attended at least 1 group per week and depressed residents attended significantly fewer groups than those who were not depressed. Residents were very frail and therefore most groups only included seated exercises. Conclusions: The intervention did not change the culture of the homes and, in the case study homes, activity levels did not change outside the exercise groups. Residents did not engage in the exercise groups at a sufficient level, and this was particularly true for those with depressive symptoms at baseline. The physical and mental frailty of care home residents may make it impossible to deliver a sufficiently intense exercise intervention to impact on depressive symptoms

Relations Among Anhedonia, Reinforcement Learning, and Global Functioning in Help-seeking Youth

Dysfunction in the neural circuits underlying salience signaling is implicated in symptoms of psychosis and may predict conversion to a psychotic disorder in youth at clinical high risk (CHR) for psychosis. Additionally, negative symptom severity, including consummatory and anticipatory aspects of anhedonia, may predict functional outcome in individuals with schizophrenia-spectrum disorders. However, it is unclear whether anhedonia is related to the ability to attribute incentive salience to stimuli (through reinforcement learning [RL]) and whether measures of anhedonia and RL predict functional outcome in a younger, help-seeking population. We administered the Salience Attribution Test (SAT) to 33 participants who met criteria for either CHR or a recent-onset psychotic disorder and 29 help-seeking youth with nonpsychotic disorders. In the SAT, participants must identify relevant and irrelevant stimulus dimensions and be sensitive to different reinforcement probabilities for the 2 levels of the relevant dimension ("adaptive salience"). Adaptive salience attribution was positively related to both consummatory pleasure and functioning in the full sample. Analyses also revealed an indirect effect of adaptive salience on the relation between consummatory pleasure and both role (αβ = .22, 95% CI = 0.02, 0.48) and social functioning (αβ = .14, 95% CI = 0.02, 0.30). These findings suggest a distinct pathway to poor global functioning in help-seeking youth, via impaired reward sensitivity and RL

Identification of elderly fallers by muscle strength measures

For efficient prevention of falls among older adults, individuals at a high risk of falling need to be identified. In this study, we searched for muscle strength measures that best identified those individuals who would fall after a gait perturbation and those who recovered their balance. Seventeen healthy older adults performed a range of muscle strength tests. We measured maximum and rate of development of ankle plantar flexion moment, knee extension moment and whole leg push-off force, as well as maximum jump height and hand grip strength. Subsequently, their capacity to regain balance after tripping over an obstacle was determined experimentally. Seven of the participants were classified as fallers based on the tripping outcome. Maximum isometric push-off force in a leg press apparatus was the best measure to identify the fallers, as cross-validation of a discriminant model with this variable resulted in the best classification (86% sensitivity and 90% specificity). Jump height and hand grip strength were strongly correlated to leg press force (r = 0.82 and 0.59, respectively) and can also be used to identify fallers, although with slightly lower specificity. These results indicate that whole leg extension strength is associated with the ability to prevent a fall after a gait perturbation and might be used to identify the elderly at risk of falling