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Biomedical subjects

M S Thompson

Publications and source records attributed to M S Thompson.

At least 19 recordsLinked to original sources
PubMed2006

Digital image correlation: a technique for determining local mechanical conditions within early bone callus.

Local mechanical conditions are known to play a role during the regeneration of musculoskeletal tissues, and histomorphometrical investigations of the time course of healing have enabled specific conclusions regarding the mechanosensitivity of tissue differentiation. However, the mechanism for this influence is not clearly understood. In order to extend this analysis, it is essential to link local histological understanding with direct characterisation of the local mechanical environment. Digital image correlation (DIC) is a computer-based image analysis technique that enables the non-contact measurement of strains on material surfaces and is finding application in many areas of biomechanics. Here we report a DIC technique to investigate the local distribution of mechanical strain within regenerating soft tissue sections. We provide exemplary data from analysis of a section of sheep bone callus. An assessment of displacement measurement accuracy gave an RMS error of 4.2 microm, corresponding to an estimated strain error of 1.4%. The sections showed concentrations of up to four times the applied strain and comparison of the strain patterns with histological analysis confirmed that these concentrations reflected boundaries between hard and soft callus.

Animals↗
PubMed2005

Gait evaluation: a tool to monitor bone healing?

BACKGROUND: Current clinical methods for monitoring fracture healing are often invasive and inaccurate. This paper evaluates the use of a pressure sensitive platform to improve monitoring. METHODS: Standardised 3 mm diaphyseal bone defects were created in the right tibia of 64 female sheep and stabilised with either a rigid monolateral external fixator or a more flexible variant. Over a nine week healing period gait parameters were measured using a pressure sensitive platform and interfragmentary movements at the fracture site were monitored. Frequency spectra were calculated for the ground reaction forces. The tibiae were tested biomechanically after sacrifice and callus sections were analysed histomorphometrically. FINDINGS: All animals unloaded the operated and overloaded the contralateral hindlimb. Callus mineralisation and stiffness, as well as limb loading increased during healing whilst interfragmentary movements were reduced. Larger interfragmentary movements resulted in a slower fracture healing rate as documented histologically and biomechanically. Frequency analysis showed upto 14 dB loss of power at frequencies associated with bone mechanotransduction at four weeks postoperatively, reducing to a 3 dB loss at nine weeks. INTERPRETATION: Gait analysis is a valuable tool for monitoring the course of fracture healing. Different fixation stiffnesses caused different initial interfragmentary movements leading to different healing rates. Ground reaction forces were strongly related to the course of callus mineralisation and thus directly reflected the recovery of stiffness at the fracture site. Reduced levels of loading frequencies that may affect bone healing persist to nine weeks postoperatively.

Analysis of Variance↗
PubMed2005

Angle stable locking reduces interfragmentary movements and promotes healing after unreamed nailing. Study of a displaced osteotomy model in sheep tibiae.

BACKGROUND: Large interfragmentary movements may delay bone-healing. The hypothesis of the present study was that a reduction of interfragmentary movements, especially of torsional rotation and bending angles, would support the healing process and lead to improved healing following unreamed tibial nailing. The objective of this study was to investigate healing of an unstable tibial osteotomy site following stabilization with unreamed nailing with a modified tibial device that had angle stable holes for the locking bolts. We compared those findings with healing after stabilization of such sites with standard unreamed tibial nailing. The duration of the study period was nine weeks. METHODS: The site of a standardized displaced osteotomy (3-mm gap) in twelve ovine tibiae was stabilized with unreamed tibial nailing: six animals were treated with a modified nail that had angle stable holes for the locking bolts, and six were treated with standard unreamed tibial nailing. In vivo gait analysis with optical measurements of interfragmentary movements and simultaneous measurements of ground reaction parameters were performed three days after the operation and once weekly afterward. After the animals were killed at nine weeks, the treated and contralateral tibiae were explanted, the implants were removed, and radiographs were made and evaluated for bridged cortices. Each pair of tibiae was also mechanically tested until torsional failure, after which the whole callus region was subjected to histological and histomorphometric analysis. RESULTS: Throughout the examination period, the interfragmentary movements in all directions were significantly smaller in the group treated with the angle stable tibial nail than they were in the group treated with standard unreamed tibial nailing. The limbs treated with the angle stable tibial nails returned to almost full weight-bearing during the period of the investigation, whereas those treated with standard nailing did not. Histomorphometric analysis, radiographic data, and mechanical testing showed superior bone-healing following treatment with the angle stable tibial nail. CONCLUSIONS: Use of an angle stable tibial nail may help to reduce interfragmentary movements in vivo and thus lead to superior bone-healing compared with that following standard unreamed tibial nailing.

Analysis of Variance↗
PubMed2004

A comparison of structural and mechanical properties in cancellous bone from the femoral head and acetabulum.

Mechanical interlock obtained by penetration of bone cement into cancellous bone is critical to the success of cemented total hip replacement (THR). Although acetabular component loosening is an important mode of THR failure, the properties of acetabular cancellous bone relevant to cement penetration are not well characterized. Bone biopsies (9 mm diameter, 10 mm long) were taken from the articular surfaces of the acetabulum and femoral head during total hip replacement. After mechanical and chemical defatting the two groups of bone specimens were characterized using flow measurement, mechanical testing and finally serial sectioning and three-dimensional computer reconstruction. The mean permeabilities of the acetabular group (1.064 x 10(-10) m2) and femoral group (1.155 x 10(-10) m2) were calculated from the flow measurements, which used saline solution and a static pressure of 9.8 kPa. The mean Young's modulus, measured non-destructively, was 47.4 MPa for the femoral group and 116.4 MPa for the acetabular group. Three-dimensional computer reconstruction of the specimens showed no significant differences in connectivity and porosity between the groups. Results obtained using femoral head cancellous bone to investigate bone cement penetration and fixation are directly relevant to fixation in the acetabulum.

Acetabulum↗
PubMed2002

Effects of acetabular resurfacing component material and fixation on the strain distribution in the pelvis.

A 3D finite element (FE) model of an implanted pelvis was developed as part of a project investigating an all-polymer hip resurfacing design. The model was used to compare this novel design with a metal-on-metal design in current use and a metal-on-polymer design typical of early resurfacing implants. The model included forces representing the actions of 22 muscles as well as variable cancellous bone stiffness and variable cortical shell thickness. The hip joint reaction force was applied via contact modelled between the femoral and acetabular components of the resurfacing prosthesis. Five load cases representing time points through the gait cycle were analysed. The effect of varying fixation conditions was also investigated. The highest cancellous bone strain levels were found at mid-stance, not heel-strike. Remote from the acetabulum there was little effect of prosthesis material and fixation upon the von Mises stresses and maximum principal strains. Implant material appeared to have little effect upon cancellous bone strain failure with both bended and unbonded bone-implant interfaces. The unbonded implants increased stresses in the subchondral bone at the centre of the acetabulum and increased cancellous bone loading, resembling behaviour obtained previously for the intact acetabulum.

Acetabulum↗
PubMed2000

Acetabular morphology and resurfacing design.

The bony surfaces of 18 archaeological hemipelves were scanned using a 3D laser surface scanner and CyDir software on a Silicon Graphics workstation. The acetabular area was selected and point data from the approximately spherical bone surface saved. These data were input to a MATLAB routine that calculated the radius and centre of the best-fit sphere. The goodness of fit was estimated using the mean and standard deviation of the distance of the bone surface points from the sphere surface. Eight points, at approximately equal distances around the acetabular rim, were selected with reference to bony landmarks. A plane containing three of these points served as an orientation reference plane. The vectors joining the eight rim points to the centre of the best-fit sphere were found. The angles between these vectors and the normal to the reference plane were calculated. Paired angles were summed to give the angle subtended by the acetabular rim in four directions. The overall mean angle was 158 degrees (range of mean angles 145 degrees -173 degrees ). The largest individual angles, some exceeding 180 degrees, were in the superior-inferior direction, while the mean angle in the anterior-posterior direction, i.e. that controlling flexion-extension, was 152 degrees. Males had larger subtended angles than females, although the difference was not statistically significant. Simulated reaming increased all angles by approximately 10 degrees. The subtended angles are important parameters in the design of the acetabular component of a hip replacement and particularly important in resurfacing hip replacement when the volume available is tightly constrained.

Acetabulum↗
PubMed2000

Determination of the cDNA sequence and mRNA expression of interleukin-1 receptor antagonist in horses.

OBJECTIVE: To determine the complementary DNA (cDNA) sequence of interleukin-1 receptor antagonist (IL-1ra) in horses and compare messenger RNA (mRNA) expression of IL-1ra among horses of various breeds. SAMPLE POPULATION: Blood samples from neonatal and adult horses examined for a variety of diseases. PROCEDURE: A polymerase chain reaction procedure was used to amplify a 220 base pair (bp) portion of the genomic DNA. The upstream and downstream regions of the cDNA sequence were determined by means of 5' and 3' rapid amplification of cDNA ends (RACE) procedures. Northern blot hybridization was used to examine steady-state mRNA expression of IL-1ra. RESULTS: The consensus sequence of the cDNA obtained with the 5'-RACE procedure and the sequence for the 220 bp portion of the genomic DNA represented the putative sequence for secreted IL-1ra. The predicted secreted IL-1ra amino acid sequence contained 176 residues with an in-frame stop codon; the N-terminal 25 amino acid residues resembled the signal peptide reported for human secreted IL-1ra. An approximately 1.3 kilobase pair (kb) band that represented a portion of the 3' end of the coding region and the 3' untranslated region was obtained by use of the 3' -RACE procedure. Northern blot hybridization detected a 1.6 kb transcript in blood RNA from adult Arabian, Belgian, Thoroughbred, and Standardbred horses. CONCLUSIONS: Results suggest that the DNA for equine secreted IL-1ra has a short (29 bp) 5' untranslated region, a 534 bp coding region, and a long (approximately 1,080 bp) untranslated region.

Amino Acid Sequence↗
PubMed1999

Use of rutin for medical management of idiopathic chylothorax in four cats.

Four cats with idiopathic chylothorax were given rutin. Three of the 4 cats had clinical improvement, and complete resolution of chylous effusion was evident in 2 cats. Idiopathic chylothorax in cats is a condition that may be difficult to resolve with medical or surgical treatment. Currently, thoracic duct ligation is considered the preferred technique, but expense and a guarded prognosis for resolution may make this procedure undesirable to cat owners. Rutin administration may offer an alternative to traditional treatments or may be useful as an adjunctive treatment.

Animals↗
PubMed1999

Compositional and structural control in bone regenerative coatings.

The development of a low-temperature method of producing bioactive coatings for medical implants has been shown to bypass the problems associated with high temperature processing routes, in particular the appearance of amorphous phases and non-stoichiometric hydroxyapatite (HA), and delamination of the coating from the substrate. An electric field/aqueous solution technique for producing adherent, crack-free calcium phosphate coatings on titanium and stainless steel substrates is described. The characteristics of the coating are a function of electrode spacing, supersaturation, temperature and current and voltage conditions. Scanning electron microscopy (SEM) characterized the surface morphology of the coatings, which were shown to be HA. The possibility of producing a coating of carbonate-substituted HA having the same chemical composition as bone apatite, and forming at physiological temperatures, has also been demonstrated. The size of the microstructure decreased and the morphology changed as the carbonate ion concentration in the calcium and phosphate ion solution increased.

Journal Article↗
PubMed1998

Cloning and genetic mapping of zebrafish BMP-2.

The BMP family of polypeptide growth factors has been shown to play diverse roles in establishing embryonic patterning and tissue fates. We report the cloning of the zebrafish homologue of BMP-2, examine its expression during embryogenesis, and find that it is localized to the distal end of the long arm of zebrafish chromosome 20. A missense mutation of the bmp2 gene has recently been shown to be responsible for the early dorsalized phenotype of the zebrafish swirl mutant [Kishimoto et al., 1997]. Given the dynamic expression of bmp2 in the developing embryo and the complex interactions of BMP signaling response in vertebrates, it is possible that other mutant phenotypes, due to altered bmp2 gene expression, will eventually map to or interact with this genetic locus.

Amino Acid Sequence↗
PubMed1998

Moment arms of the digital flexor tendons at the wrist: role of differential loading in stability of carpal tunnel tendons.

When a flexor digitorum superficialis tendon crossing a flexed or extended wrist has a load applied to it in excess of that applied to adjacent tendons, that tendon may translate across the carpal tunnel. In 6 cadaver specimens, each of the 9 carpal tunnel tendons was loaded with a baseline tension of 85 g and the moment arms of the flexor pollicis longus and the 4 flexor digitorum superficialis tendons were determined. Applying a higher 540-g load to individual flexor digitorum superficialis tendons and the flexor pollicis longus while loading the remaining tendons with the baseline 85-g tension significantly changed the moment arms from those measured under baseline load. The results demonstrated that tendons with applied differential loads in the carpal tunnel shift their positions, as revealed by their changing moment arms.

Analysis of Variance↗
PubMed1996

Contraceptive implants: long acting and provider dependent contraception raises concerns about freedom of choice.

David Bromham's editorial on contraceptive implants ignores the wider issues to voice concern that trial by media could limit contraceptive choice by jeopardising research into new methods. However, it is more beneficial to the public for points of conflict to be debated openly. Furthermore, the impetus for research into new contraceptive technology is driven by profit and political motives and is only marginally affected by the media. Implanted contraceptives may increase the choice of contraceptive methods, but they put control of fertility increasingly into the hands of the medical profession. Herein lies their greatest problem: their potential to increase providers' control over clients' choice. There is the danger that certain groups of women may be targeted for their use: in the United States the coercive use of Norplant for mothers receiving welfare benefit has been suggested. Long acting contraceptives are a contraceptive of choice only when they are available without pressure, as part of a wider menu; when instant removal on request is guaranteed; and when there is an open and free flow of information and opinions between users, health professionals, and special interest groups.

Biomedical Research↗
PubMed1992

The impact of formal, informal, and societal support networks on the psychological well-being of black adolescent mothers.

Although several researchers argue that informal support systems provide economic and psychological resources for black families, little empirical research is available to inform policy and intervention programs. This article examines the impact of informal, formal, and societal support systems on the mental health of black adolescent mothers. Using the social work generalist theoretical framework, several types of resources are considered separately to determine whether they contribute similarly to psychological well-being. Data from a survey of black teenage mothers show that both lay and professional supports were important for the young mother's psychological well-being. Support from a male partner, caseworker contact, and membership in a support group decreased psychological distress and depression. Support from the male partner also enhanced psychological well-being. Support from friends, on the other hand, was associated with higher levels of psychological distress. A professional service plan that effectively incorporates informal and societal supports in a complementary manner offers the best possibility for reducing the distress of black teenage mothers.

Adolescent↗
PubMed1988

The cost effectiveness of auranofin: results of a randomized clinical trial.

In a 6-month randomized trial at 14 sites, the cost effectiveness of auranofin (AF) treatment for patients with rheumatoid arthritis was gauged in comparison with placebo. Measures of global health and of impacts on daily life suggest that the benefits of disease modification outweigh adverse effects after 4 and 6 months of treatment (p less than 0.01), with negligible differences between placebo and treated patients after 1 and 2 months. Additional medical costs directly associated with AF treatment amounted to $778/patient annually. Observed differences in less direct medical costs, help received, and earnings were not statistically significant.

Adult↗