Can FES-rowing mediate bone mineral density in SCI: a pilot study.

STUDY DESIGN: A single case study. OBJECTIVES: To compare proximal tibia trabecular bone mineral density (BMD) of a participant with complete spinal cord injury (SCI), long-termed functional electrical stimulation-rowing (FES-R) trained, with previously reported SCI and non-SCI group norms. To estimate lower limb joint contact forces (JCFs) in the FES-R trained participant. SETTING: UK University and orthopaedic hospital research centre. METHODS: Bilateral proximal tibial trabecular BMD of the FES-R trained participant was measured using peripheral quantitative computerised tomography, and the data were compared with SCI and non-SCI groups. An instrumented four-channel FES-R system was used to measure the lower limb JCFs in the FES-R trained participant. RESULTS: Structurally, proximal tibial trabecular BMD was higher in the FES-R trained participant compared with the SCI group, but was less than the non-SCI group. Furthermore, left (184.7 mg cm(-3)) and right (160.7 mg cm(-3)) BMD were well above the threshold associated with non-traumatic fracture. The knee JCFs were above the threshold known to mediate BMD in SCI, but below threshold at the hip and ankle. CONCLUSION: As pathological fractures predominate in the distal femur and proximal tibia in chronic SCI patients, the fact that the FES-R trained participant's knee JCFs were above those known to partially prevent bone loss, suggests that FES-R training may provide therapeutic benefit. Although the elevated bilateral proximal tibial BMD of the FES-R participant provides circumstantial evidence of osteogenesis, this single case precludes any statement on the clinical significance. Further investigations are required involving larger numbers and additional channels of FES to increase loading at the hip and ankle.

Changes in the structural and material properties of the tibia in patients with spinal cord injury.

STUDY DESIGN: A cross-sectional study. OBJECTIVES: To measure the change of structural and material properties at different sites of the tibia in spinal cord-injured patients using peripheral quantitative computerised tomography (pQCT). SETTING: Orthopaedic research centre (UK). METHODS: Thirty-one subjects were measured--eight with acute spinal cord injury (SCI), nine with chronic SCI and fourteen able-bodied controls. pQCT scans were performed at 2% (proximal), 34% (diaphyseal) and 96% (distal) along the tibia from the tibial plateau. Structural measures of bone were calculated, and volumetric bone mineral density (vBMD) was also measured at all three levels. Muscle cross-sectional area was measured at the diaphyseal level. RESULTS: Structurally, there were changes in the cortical bone; in the diaphysis, the shape of the cross-section changed to offer less resistance to AP bending, and the cross-sectional area of the cortical shell decreased both proximally and distally. There were corresponding changes in vBMD in the anterior aspect of the cortical diaphysis, as well as proximal and distal trabecular bone. Changes in muscle occurred more rapidly than changes in bone. CONCLUSION: There were clear changes of both structure and material at all three levels of the tibia in chronic SCI patients. These changes were consistent with specific adaptations to reduced local mechanical loading conditions. To assess fracture risk in SCI and also to monitor the effect of therapeutic interventions, the structure of the bone should be considered in addition to trabecular bone mineral density.

Phylogenetic and ecological factors influencing the number and distribution of electroreceptors in elasmobranchs.

Electroreception is found throughout the animal kingdom from invertebrates to mammals and has been shown to play an important role in prey detection, facilitating social behaviours, the detection of predators and orientation to the earth's magnetic field for navigation. Electroreceptors in elasmobranchs, the ampullae of Lorenzini, detect minute electric fields and independently process these stimuli, thereby providing spatial information to the central nervous system on the location of a source, often potential prey. The ampullae of Lorenzini are individually connected to a single somatic pore on the surface of the skin, with the spatial separation of each pore directly influencing how electrical stimuli are detected and processed. Pore abundance varies across taxonomic groups resulting in unique species-specific differences. The intricate distribution patterns created by the specific positioning of somatic pores on the head are, however, consistent within families, resulting in patterns that are identifiable at higher taxonomic levels. As elasmobranchs evolved, the electrosensory system became more complex and highly specialized, which is evident by a general trend of increasing pore abundance over time. The elasmobranch electrosensory system has evolved to operate efficiently under the environmental conditions of the particular habitat in which a species lives. For example, reduced pore abundance is evident in oceanic pelagic elasmobranchs, for whom visual cues are thought to be of great importance. Pore abundance and spatial distribution may be influenced by multiple factors including head morphology, phylogeny, feeding behaviour and habitat.

Species, sex, size and male maturity composition of previously unreported elasmobranch landings in Kuwait, Qatar and Abu Dhabi Emirate.

This paper presents data from the first major survey of the diversity, biology and fisheries of elasmobranchs in the Persian (Arabian) Gulf. Substantial landings of elasmobranchs, usually as gillnet by-catch, were recorded in Kuwait, Qatar and the Emirate of Abu Dhabi (part of the United Arab Emirates), although larger elasmobranchs from targeted line fisheries were landed in Abu Dhabi. The elasmobranch fauna recorded was distinctive and included species that are undescribed, rare and have a highly restricted known distribution. Numerical abundance was dominated by sharks (c. 80%), of which carcharhinids were by far the most important. The milk shark Rhizoprionodon acutus and whitecheek shark Carcharhinus dussumieri together comprised just under half of all recorded individuals. Around 90% of recorded sharks were small (50-90 cm total length, L(T) ) individuals, most of which were mature individuals of species with a small maximum size (<100 cm L(T) ), although immature individuals of larger species (e.g. Carcharhinus sorrah and other Carcharhinus spp.) were also important. The most frequently recorded batoid taxa were cownose rays Rhinoptera spp., an undescribed whipray, and the granulated guitarfish Rhinobatos granulatus. The first size, sex and maturity data for a wide range of Gulf elasmobranch species are presented (including L(T) at 50% maturity for males of four shark species) and include some notable differences from other locations in the Indo-West Pacific Ocean. A number of concerns regarding the sustainability of the fishery were highlighted by this study, notably that most of the batoid species recorded are classed by the IUCN Red List as vulnerable, endangered, data deficient or not evaluated. Despite their considerable elasmobranch landings, none of the three countries sampled have developed a 'Shark Plan' as encouraged to do so under the FAO International Plan of Action: Sharks. Furthermore, Kuwait and Qatar currently report zero or no elasmobranch landings to the FAO.

The relationship between physical activity and leg health in the broiler chicken.

1. The relationship between the physical activity and leg health of broiler chickens was assessed on a semi-commercial scale. 2. Three batches of birds (2128 per batch) were raised under two lighting regimes during the photoperiod; either a step-wise change of light intensity alternating between an illuminance of 200 and 10 lx or a constant illuminance of 10 lx. The activity of focal individuals (24 per batch) was observed at 2, 4 and 6 weeks of age, and leg health assessed weekly, based on gait score, the prevalence of burns on the hock and foot pad, and angulation and rotation of the leg at the intertarsal joint. Cortical bone density and thickness and area moments of inertia of the mid-physis tibiotarsus were measured post mortem at 6 weeks of age. 3. The step-wise change in light intensity did not affect overall performance, activity or leg health. 4. An individual bird's activity did not affect its gait score, the prevalence of hock burn or foot pad burn, cortical density or thickness or shape of the tibiotarsus. Sex of the bird was the only factor to affect significantly the area moment of inertia in the horizontal and vertical planes of the tibiotarsus, with females showing a lower moment of inertia for both. No variable had a significant effect on cortical density or thickness. Mean cortical density was low across all birds and may indicate that, when allowed to move freely as much or as little as they choose, broiler chickens do not exercise enough or do not perform the higher impact activities required to affect bone quality. 5. These findings imply that the activity of broiler chickens raised on a semi-commercial scale is unaffected by step-wise changes in light intensity and that other husbandry measures are needed to raise activity and hence improve leg health.

In vitro and in vivo biological responses to a novel radiopacifying agent for bone cement.

Iodixanol (IDX) and iohexol (IHX) have been investigated as possible radiopacification agents for polymethylmethacrylate (PMMA) bone cement, to replace the currently used barium sulphate and zirconia. IDX and IHX are both water-soluble iodine-based contrast media and for the last 20 years have been used extensively in clinical diagnostic procedures such as contrast media enhanced computed tomography, angiography and urography. One of the major reasons to remove the current radiopacifying agents is their well-documented cytotoxicity and their potential to increase bone resorption. Using in vitro bone resorption assays, the effect of PMMA particles plus IDX or IHX to induce osteoclast formation and lacunar resorption on dentine slices has been investigated. These responses have been compared with the in vitro response to PMMA particles containing the conventional radiopacifying agents, that is, barium sulphate and zirconia. In parallel, the in vivo reaction, in terms of new bone formation, to particles of these materials has been tested using a bone harvest chamber in rabbit tibiae. In vitro cell culture showed that PMMA containing IHX resulted in significantly less bone resorption than PMMA containing the conventional opacifiers. In vivo testing, however, showed no significant differences between the amounts of new bone formed around cement samples containing the two iodine-based opacifying agents in particulate form, although both led to fewer inflammatory cells than particles of PMMA containing zirconia. Our results suggest that a non-ionic radiopacifier could be considered as an alternative to the conventional radiopacifying agents used in biomaterials in orthopaedic surgery.

Assessment of protein nutrition in surgical patients--the value of anthropometrics.

In order to evaluate the reliability of anthropometry in assessing protein stores we have compared, in 10 normal adults and 82 surgical patients with varying degrees of weight loss, measurements of weight/height, arm circumference, arm muscle circumference, and arm muscle area with direct measurements of body nitrogen using in vivo neutron activation analysis. Anthropometry is reliable for the assessment of protein nutrition in groups of patients (for 100 patients 95% confidence limits are +/- 30 g nitrogen) but the magnitude of variance shown makes it inappropriate for assessing the individual as a single measurement (95% confidence limits are +/- 300 g nitrogen). Repeat measurements were made after 2 weeks on 35 patients and there was no correlation between changes in body nitrogen and changes in the anthropometric measurements. Anthropometry is not reliable in following changes in body nitrogen in individual patients over short periods of time.

Rapid effects of parathyroid hormone(1-34) and prostaglandin E2 on bone blood flow and strontium clearance in the rat in vivo.

The vascular effects of noradrenaline, ATP, parathyroid hormone (PTH) and prostaglandin E2 (PGE2) were investigated in the rat. Additionally, the exchange of mineral ions between bone and blood was assessed by measuring strontium clearance, with the aim of investigating whether the vascular effects of these agents altered uptake of mineral ions or if this exchange could be changed independently of blood flow. Radioactive microspheres and 85Sr were used to establish bone blood flow and mineral clearance. Measurements of bone blood flow and arterial pressure were made in each animal and used to calculate vascular resistance. A measurement of 85Sr clearance was also obtained. Arterial blood pressure was significantly affected by noradrenaline (P less than or equal to 0.003) and ATP (P less than or equal to 0.015). Additionally, noradrenaline significantly (P less than or equal to 0.03) reduced bone blood flow. This decrease was related to a significant increase in vascular resistance. Arterial blood pressure and bone blood flow were significantly reduced by both bovine PTH(1-34) (P less than or equal to 0.001, P less than or equal to 0.02) and PGE2 (P less than or equal to 0.005, P less than or equal to 0.001). Vascular resistance to bone was increased by both agents but this was only statistically significant in the case of PGE2 (P less than or equal to 0.01). A significant (P less than or equal to 0.001) reduction in strontium was also produced by PGE2. In each group the relationship between bone blood flow and strontium clearance was then analysed.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of blood flow in tibial cortical bone: an experimental investigation using microspheres.

The distribution of tibial blood flow was measured by injecting approximately (600-1000) x 10(3) 15 mu microspheres, labelled with either tin-113 (113Sn) or cobalt-57 (57Co) into femoral arteries of five mature greyhounds. The diaphyseal cortex, stripped of periosteum and devoid of marrow, was sawn into 40 pieces (10 transverse sections x 4 anatomical quarters/section). Relative deposition densities of the 113Sn microspheres in 40 pieces of cortex were found. These values, together with their associated masses, proved, from a statistical point of view, that flow rate heterogeneity was substantial in the diaphysis. In particular, for the diaphyseal cortex, distribution of relative deposition densities (flow rates) in six bones was found to be positively-skewed with a relative dispersion ((SD/mean) x 100) of approximately 40%.

Water uptake and release from iodine-containing bone cement.

Water uptake and release characteristics of PMMA cement containing the water-soluble contrast media iohexol or iodixanol have been investigated. The water uptake study revealed that iohexol had the highest uptake of water (3.7%) and that iodixanol had an uptake close to that of Palacos R (2.3% and 1.9%). The curves obtained showed the materials to follow classic diffusion theory, with an initial linearity with respect to t(1/2) making it possible to calculate the diffusion coefficients. This showed iohexol to have the lowest diffusion coefficient, Palacos R the highest, and iodixanol close to that of Palacos R. The release study showed that more iohexol than iodixanol was released from the bone cement; the long-term release was above 25 microg/mL for iohexol compared to slightly above 10 microg/mL for iodixanol. A microCT investigation showed that the risk of developing an observable radiolucent zone is negligible.

The accuracy of total body nitrogen determined by neutron activation analysis.

Experiments have been performed to validate the technique of determining total body nitrogen by measuring the induced activity of 13N produced by the reaction of 14 MeV neutrons with nitrogen. Firstly, the accuracy of determining the counts due to nitrogen was studied by measuring the activities of the positron-emitting nuclides of C, Cl, K, P, and O, as well as N, produced by the irradiation of anthropomorphic phantoms with a surface neutron dose equivalent of 0.5 mSv (50 mrem). Secondly, the effect of variation of spatial sensitivity was studied by measuring the activation and detection efficiencies of small samples at many positions within an anthropomorphic phantom, and also by comparing the known amounts of nitrogen within a new type of phantom in which the elements are fixed, with the amounts measured using a calibration based on experiments with a Bush phantom in which the elements are freely diffusible within each phantom part. There was a maximum difference of only 4% between the measured and known amounts of nitrogen. It is therefore concluded that this technique provides a simple and accurate way of measuring total body nitrogen.

A distributed model of exchange processes within the osteon.

In order to understand various exchange processes within the osteon, a mathematical model to describe the system has been developed which allows for concentration gradients in the axial and radial directions as well as cellular consumption and binding to bone surface. The normal values for the model parameter are discussed and the effects of the model parameters on the behaviour of the model are investigated. This model supports the idea that diffusion alone may be an inefficient mechanism in transport between blood and osteocytes.

Changes in body weight and body protein with intravenous nutrition.

Body weight, protein, fat and water were measured before and after intravenous nutrition in 20 surgical patients. The group included both young and old patients who were suffering from a wide variety of catabolic illnesses and the period of intravenous feeding ranged from 11 to 40 days. Eight of the patients were able to take small amounts of food orally. During the period of intravenous nutrition ten patients gained significant weight although only two of these gained significant protein. Most of the weight gain was due to an increase of water. There was also a gain of water in the patients who lost weight; this water gain occurred in small daily increments over the course of treatment. It is concluded that weight gain can occur without protein gain in patients who are being fed intravenously and that body weight is not a reliable guide to changes in body protein or fat in critically ill patients receiving intravenous nutrition.

Motion characteristics of the lumbar spine in the normal population.

STUDY DESIGN: The present study investigated the dynamic motion characteristics of the lumbar spine in the normal population using a potentiometric analysis system. OBJECTIVES: To assess the ability of a triaxial potentiometric analysis system to measure dynamic motion in the lumbar spine, and to use this system to form a database of dynamic motion characteristics from which normal parameters of motion and the factors affecting this motion could be defined. SUMMARY OF BACKGROUND DATA: Spinal motion has been studied using a variety of different methods, the majority of which have been limited either in terms of reliability, accuracy, or invasiveness and many have been only of a static nature. There has been no previous study into the normal dynamic motion characteristics of the lumbar spine. METHODS: The accuracy of the system was determined by a series of tests against a calibrated engineering mill, and the reliability of the system was assessed on 10 subjects with repeated measurements over a 3-day period. Values of range of motion and angular velocity were obtained from 203 normal subjects during flexion and extension, lateral flexion, and rotation. RESULTS: The results of the calibration testing revealed excellent accuracy, and it was shown that the system was repeatable. Initial analysis of the results indicated that sex differences did exist with men having 58.4 degrees of flexion and women having 53.4 degrees. Age appeared to have an influence on motion, and a gradual reduction was seen with each decade (P < 0.001), with the 20-29-year age range having 59.5 degrees mean flexion, the 30-39-year group having 58.1 degrees, the 40-49-year group having 53.7 degrees, the 50-60-year group having 57.5 degrees, and the 60-70-year group having 45.9 degrees. Multiple regression techniques revealed that only a few factors are important with respect to motion and that these varied according to the characteristic being defined. CONCLUSIONS: Range of motion tended to be affected by age and sex, whereas velocity was only affected by distance moved, with occupation and body mass index having little or no influence on the motion. The factors identified could only account for a small proportion of the variation seen, suggesting that it is difficult to predict the motion characteristics with any degree of sensitivity.

Humoral regulation of blood flow in the vertebral endplate.

STUDY DESIGN: Blood flow in the sheep lumbar spine was measured. OBJECTIVES: The effect of vasoactive agents, noradrenaline and acetylcholine, on blood flow adjacent to the disc--bone interface was determined. SUMMARY OF BACKGROUND DATA: The main route for disc nutrition is through the vertebral endplate. Although the vascular anatomy in this region has been well described, its response to neurohumoral influences has not been quantified. METHODS: Blood flow in bone adjacent to the lumbar intervertebral discs was measured using the microsphere technique before and after infusions of noradrenaline and acetylcholine in two groups of five female sheep. Systemic arterial pressure was measured during each infusion. RESULTS: Vertebral bone blood flow was unchanged during noradrenaline infusion, but increased by 60% during acetylcholine infusion. This was associated with a significant decrease in systemic arterial pressure. CONCLUSIONS: These data are consistent with the existence of muscarinic receptors in vessels of the vertebral endplate, which suggests that the vasculature may influence disc nutrition.

The acute vascular response to intramedullary reaming. Microsphere estimation of blood flow in the intact ovine tibia.

The tibial nutrient artery supplies 62% of cortical blood flow in the diaphysis and normal blood flow is centrifugal (Willans 1987). Intramedullary reaming destroys the nutrient artery and injures the endosteal surface of the cortex. Trueta (1974) suggested that the direction of blood flow can reverse from centrifugal to centripetal after loss of the endosteal supply. We examined this hypothesis by measuring cortical and periosteal blood flow after intramedullary reaming of the tibia in eight sheep, using 57Co radiolabelled microspheres. The unreamed contralateral tibiae served as a control group. Thirty minutes after reaming there was no significant change in cortical blood flow, but a sixfold increase in the periosteal flow. Our study confirms Trueta's hypothesis; after trauma or in other pathological states, flow can become centripetal.

The effect of devascularisation upon early bone healing in dynamic external fixation.

We examined the effect of periosteal devascularisation upon the early healing of osteotomies of sheep tibiae held in an instrumented external fixation system with an axial stiffness of 240 N/mm. At 14 days, cortical blood flow measured by the microsphere technique was 19.3 ml/min/100g in the well-vascularised osteotomies, but only 1.7 ml/min/100g in the devascularised osteotomies, despite an increase in medullary flow (p less than 0.0005). Delay in healing of the devascularised osteotomies was suggested by an in vivo monitoring system and confirmed by post-mortem mechanical testing. We suggest that the osteogenic stimulus of dynamic external fixation is dependent on the early restoration of cortical blood flow in devascularised fractures.

Nitric oxide in fracture repair. Differential localisation, expression and activity of nitric oxide synthases.

Our aim was to investigate whether nitric oxide synthase (NOS) isoforms, responsible for the generation of NO, are expressed during the healing of fractures. To localise the sites of expression compared with those in normal bone we made standardised, stabilised, unilateral tibial fractures in male Wistar rats. Immunostaining was used to determine the precise tissue localisation of the different NOS isoforms. Western blotting was used to assess expression of NOS isoform protein and L-citrulline assays for studies on NOS activity. Control tissue was obtained from both the contralateral uninjured limb and limbs of normal rats. Immunohistochemistry showed increased expression of endothelial NOS (eNOS) to be strongest in the cortical blood vessels and in osteocytes in the early phase of fracture repair. Western blot and image analysis confirmed this initial increase. Significantly elevated calcium-dependent NOS activity was observed at day 1 after fracture. Inducible NOS (iNOS) was localised principally in endosteal osteoblasts and was also seen in chondroblasts especially in the second week of fracture healing. Western blotting showed a reduction in iNOS during the early healing period. Significantly reduced calcium-independent NOS activity was also seen. No neuronal NOS was seen in either fracture or normal tissue. Increased eNOS in bone blood vessels is likely to mediate the increased blood flow recognised during fracture healing. eNOS expression in osteocytes may occur in response to changes in either mechanical or local fluid shear stress. The finding that eNOS is increased and iNOS reduced in early healing of fractures may be important in their successful repair.

A new in-vitro model to investigate antibiotic penetration of the intervertebral disc.

We have studied the ability of a range of antibiotics to penetrate intervertebral disc tissue in vitro, using a mouse disc model. Equilibrium concentrations of antibiotics incorporated into the entire disc were determined by bioassay using a microbial growth-inhibition method. Uptake was significantly higher with positively-charged aminoglycosides compared with negatively-charged penicillins and cephalosporins. Uncharged ciprofloxacin showed an intermediate degree of uptake. Our results support the hypothesis that electrostatic interaction between charged antibiotics and negatively-charged glycosaminoglycans in the disc is an important factor in antibiotic penetration, and may explain their differential uptake.

Aseptic loosening of total hip replacement. Macrophage expression of inducible nitric oxide synthase and cyclo-oxygenase-2, together with peroxynitrite formation, as a possible mechanism for early prosthesis failure.

Aseptic loosening is a major cause of failure of total hip arthroplasty. The adverse tissue response to prosthetic wear particles, with activation of cytokine and prostanoid production, contributes to bone loss around the implants. We have investigated the possibility that inducible nitric oxide synthase (iNOS) and cyclo-oxygenase-2 (COX-2) are expressed in macrophages in the pseudomembrane at the bone-implant interface, thereby contributing to the periprosthetic bone resorption. We also assessed whether peroxynitrite, a nitric oxide (NO)-derived oxidant associated with cellular injury, is generated in the membrane. Enzymatic activity of iNOS was measured using the arginine-citrulline assay technique and prostaglandin E2 (PGE2), as an indicator of COX-2 activity, was measured using an enzyme immunoassay. Cellular immunoreactivity for iNOS, nitrotyrosine (a marker of peroxynitrite-induced cellular injury) and COX-2 was assessed by quantitative peroxidase immunocytochemistry while immunofluorescence methods were used for subsequent co-localisation studies with CD68+ macrophages. The presence of calcium-independent iNOS activity and PGE2 production was confirmed in the homogenised interface membrane. Immunocytochemistry showed that periprosthetic CD68+ wear-debris-laden macrophages were the most prominent cell type immunoreactive for iNOS, nitrotyrosine and COX-2. Other periprosthetic inflammatory and resident cell types were also found to immunolocalise nitrotyrosine thereby suggesting peroxynitrite-induced protein nitrosylation and cellular damage not only in NO-producing CD68+ macrophages, but also in their neighbouring cells. These data indicate that both iNOS and COX-2 are expressed by CD68+ macrophages in the interface membrane and peroxynitrite-induced cellular damage is evident in such tissue. If high-output NO and peroxynitrite generation were to cause macrophage cell death, this would result in the release of phagocytosed wear debris into the extracellular matrix. A detrimental cycle of events would then be established with further phagocytosis by newly-recruited inflammatory cells and subsequent NO, peroxynitrite and prostanoid synthesis. Since both NO and PGE2 have been implicated in the induction and maintenance of chronic inflammation with resulting loss of bone, and peroxynitrite in the pathogenesis of disease states, they may be central to the pathogenesis of aseptic loosening.