bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Flow Visualization Study of Prosthetic Aortic and Mitral Heart Valves in a Model of the Aorta and Left Heart
Authors: Wright J T M , Temple L J 
Published: February 2007

An in vitro flow visualization study has been carried out on a range of aortic and mitral valve prostheses mounted in rigid, transparent models of the aorta and left ventricle, The valves were subjected to pulsatile flow and the flow patterns produced by each valve were visualized by injecting multi-dye streams into the valve orifice, or by observing illuminated particles suspended in the flow. The patterns were recorded by still photography and high speed cinematography. In the mitral region each tilting disc valve produced a large vortex which dominated the ventricular cavity. By contrast disc and ball valves each produced an annular vortex, and the bioprosthesis produced a central flow. In the aortic region the flow patterns produced by a tilting disc valve depended on the orientation of the valve in the aorta. The aortic ball valve was found to produce less flow disturbance than either tilting disc valve or the porcine bioprosthesis.
Elastohydrodynamic Lubrication in Human Joints
Authors: Higginson G. R. 
Published: February 2007

Recent developments in the analysis of elastohydrodynamic lubrication (EHL) of solids covered by soft layers, are applied to the big load-bearing human joints. It is concluded that the chances of generating a full film by conventional rolling/sliding EHL are small; but for loads of short duration the squeeze film mechanism looks very promising. This address, delivered at an Ordinary Meeting of the Institution, in London, on 2 November 1977 is reprinted from Proc. Instn mech. Engrs, 191, 217, (1977).
Diagnostic Ultrasound in Medicine
Authors: Railton R. , Shaw A. 
Published: February 2007

The application of ultrasonic technology in medicine has taken place in the last fifteen years and was made possible by far sighted and determined individuals who initially made use of industrial flaw detection equipment. In the last decade medical ultrasonics has developed into a multi-million pound business and has become an important aid to diagnosis and patient management. In this article we describe the use of ultrasonics as a method of investigating the internal structures of the body for diagnostic purposes. Other applications of ultrasonics in medicine include humidifiers and the use of instruments based on the Doppler principle for measuring the velocity of blood flowing in vessels.
Fatigue Strength of Cobalt-Base Alloys with High Corrosion Resistance for Artificial Hip Joints
Authors: Lorenz M. , Semlitsch M. , Panic B. , Weber H. , Willert H. G. 
Published: February 2007

Loosening of the anchorage in the bone is a problem in hip-joint arthroplasty which up to now has not been entirely solved. In the loosened condition, anchorage stems of artificial joints are subject to alternating overload which causes rupture if the fatigue strength is exceeded by the stress amplitude. At Sulzer a hip-joint anchorage stem made from wrought CoNiCrMo alloy Protasul-10 has been developed which has substantially higher fatigue strength than stems made from stainless steel of grade AISI-316L or CoCrMo cast alloy. It is therefore essentially safe from fatigue cracking and this offers the possibility of significantly easier removal in case of re-operation after loosening. This paper deals with some rules to be observed in choice or development of materials for long-term implants subject to fatigue. The results of laboratory investigations on the fatigue behaviour of cobalt-base alloys for surgical implants are discussed.
Dimensions of the Metacarpo-Phalangeal Joint with Particular Reference to Joint Prostheses
Authors: Unsworth A , Alexander W J 
Published: February 2007

Sixty metacarpo-phalangeal joints were dissected and investigated to determine the shape, size and position of the articular surfaces with respect to the medullary canals of the metacarpal and the phalanx. The results show that the articular surfaces of the metacarpo-phalangeal joint have a single centre of rotation in the sagital plane and in the transverse plane. The joints of the little and ring fingers have radii of curvature in the sagital and transverse planes, which are almost equal (within 1.6 per cent) while those radii of the middle finger varied by 9 per cent. The index finger had a variation in radius from the sagital to the transverse plane of almost 13 per cent; the sagital plane radius being the greatest. This observation is the opposite of the other joints where the transverse radius is the greater one. The overall widths of the metacarpal heads were seen to vary from 13 mm in the little finger of females to 17 mm in the index finger of males (average). The medullary canals had axes which were not coincident with the centre of rotation of the joint but up to 3 mm displaced from it. These dimensional differences have important implications in prosthesis design.
A Study of the Duration of Load-Bearing under Different Areas of the Foot
Authors: Miller G F , Stokes I A F 
Published: February 2007

This paper presents a method of studying the time course of load-bearing under selected areas of the foot during walking. The suitability of the sensors and the reliability of the technique have been demonstrated. The study has shown that the pattern of load-bearing in normal individuals varies from step to step and from day to day. The pattern of load-bearing in normal feet has been compared with the pattern in the feet of patients with symptomatic hallux valgus and significant differences have been demonstrated. The method is currently being used to monitor the changes occurring after surgery for hallux valgus. The early results of this study suggest that it is possible to detect changes which correlate with those to be expected from clinical observation.
External Fracture Fixation—the Analysis and Design of a New System
Authors: Kenwright J , Harris J D , Evans M 
Published: February 2007

External skeletal fixation of long bone fractures is the procedure of choice for the treatment of certain clearly established types of fracture. In particular, it is appropriate when the skin and soft tissue at the site of the fracture is at risk and requires careful management. For sound bone union to be achieved correct orientation and stability of the fracture is needed. A rigid fixation method is therefore required, and this rigidity determines the degree of post-operative mobility that the patient can exercise during the healing phase. A single-sided fixation system when applied, for example, to the medial aspect of the tibia, which gives adequate skeletal support, would be preferred to a double-sided unit as it would not inhibit the action of muscles, would reduce the number of pin holes, and be more convenient for the patient. From experience with existing equipment available for this surgical technique, a specification to meet the performance criteria needed was drawn up, and from this a design emerged giving priority to aspects of stiffness and convenience. The report concludes with three case studies of patients treated with this fixator. A separate paper gives the results of practical tests on this fixator, with a theoretical analysis of the factors which influence stiffness in single-sided fixators, and of the strength which can be expected.
An Experimental Study of Friction and Lubrication in Hip Prostheses
Authors: O'Kelly J , Unsworth A , Dowson D , Wright V 
Published: February 2007

McKee-Farrar, Charnley and Muller prostheses have been studied in a hip function simulator using a range of silicone fluids as lubricants. Frictional resistance was measured continuously while the joints were subjected to dynamic loading. It was observed that the lubricant viscosity was very important to the mode of lubrication prevailing and that for viscosities in excess of 0.1 Pas, full fluid film lubrication was achieved. At viscosities which were less than this, mixed lubrication resulted These results can be extrapolated to the clinical situation where it was found that after hip surgery for total joint replacement, the synovial fluid produced around the prosthesis had a viscosity which was less than 0.1 Pas, and therefore could not give the most advantageous lubrication in these joints in vivo.
A Terribly Strange Bed
Authors: Morrison D 
Published: February 2007

I did not really want to write an article about something which is as yet unfinished, but, since this project is based upon principles common to the design of many features of my intensive care unit, principles which I think should be borne in mind when designing units for the future, I think that it is worth describing the evolution of the project so far. The very rapid technological advances of the past couple of decades have produced a plethora of gadgets for monitoringphysiological systems and for boosting or replacing defective systems. Many patients owe their lives to artificial ventilation, artificial kidneys, etc. We have become very ambitious in our treatment of life threatening acute illness and are tackling patients with multi-system failure who would have simply been allowed to die twenty years ago. Unfortunately all advances bring new problems.
Joint Space of the Human Knee and Hip Joint under a Static Load
Authors: Terayama K , Takei T , Nakada K 
Published: February 2007

In order to study the joint contact and joint space of statically loaded human knee and hip joints, observations of serial slices of joint specimens which were frozen during the application of a load were carried out. In the intact joints, the articular cartilage surfaces did not come into direct contact with each other even under a load of more than twice that of the body weight. The minimum distance between cartilage surfaces in each specimen ranged from 0.2 to 0.6 mm. The Indian ink which was injected into the joints before the load application was squeezed out of some areas of the remaining joint space, but a dye-free fluid apparently remained in this space. Based on our findings, the definition of joint contact and the lubrication mechanism in the intact human joint have been discussed.
Properties of Wrought CoNiCrMo Alloy Protasul-10, a Highly Corrosion and Fatigue Resistant Implant Material for Joint Endoprostheses
Authors: Semlitsch M 
Published: February 2007

Loosening of prosthetic components in the bone is a problem that has not been fully explored as yet. When loosening has occurred, the metallic anchorage stem may become overloaded and in extreme cases it may ultimately lead to stem fracture if the fatigue limit of the metallic material is exceeded. In order to preclude the possibility of these undesirable fatigue fractures of loosened prosthesis stems requiring re-operations, the Sulzer research laboratories have developed wrought alloys of extremely high strength and corrosion resistance such as Protasul-10.† The chemical composition, structure, mechanical properties, corrosion resistance and present state of the art of this implant material, which has been in clinical use since 1971, are specified in national and international standards.
Wear of Artificial Joint Materials II
Authors: McKellop H 
Published: February 2007

A twelve-channel wear machine was designed for the screening of candidate materials for use in prosthetic joints, and for investigating the influence of parameters such as load, cycling rate, surface finish, sterilization dosage, and others, on the wear of conventional materials. The rationale for the design of the machine is discussed In detail with respect to the practice of using data obtained with a simplified specimen geometry to predict wear under the widely varying contact geometries in actual prosthetic joints. Three sets of experiments are described: (a) a comparison of polyethylene wear properties in the various lubricants used in previous studies, (b) tests of polyethylene against conventional prosthetic alloys to evaluate the accuracy and repeatability of the wear measurement method, and (c) a comparison of the wear properties of several polymers tested in the screening machine to the clinical performance of these materials, to evaluate the clinical significance of the laboratory test protocol. The wear machine was found to be a very reliable apparatus for providing reproducible data. The simplicity of design and its inherent reliability enabled long-term, multi-specimen tests with a variety of materials to be conducted in a reasonably short time period. Of the lubricants tested, only bovine blood serum produced wear of the same type as that observed on removed prostheses. This was considered to be an essential factor in laboratory wear tests of prosthetic materials. Wear was determined by direct weighing of the polymer specimens with correction for the effects of fluid absorption. The data thus obtained had a much higher repeatability than has been typical of previous studies of wear properties of prosthetic materials. Nevertheless, tests lasting two to three million cycles were necessary to establish accurately the very low wear rate of the polyethylene specimens, in the order of one micron per year's equivalent use of a prosthesis. This was in contrast to the range of 100-200 microns per year that has been commonly reported in the literature. However, consideration of the potential error, especially due to polymer creep, in previous wear measurement methods suggests that the value of one micron per year may in fact represent a minimum for prostheses under optimal conditions. Polyester, PTFE and Delrin polyacetal all exhibited significantly higher wear rates than polyethylene. A comparison of these results with the available data on prior clinical performance of these polymers strongly indicates that the laboratory wear model developed here provides a first-stage quantitative indication of the potential clinical performance of candidate materials.
Forces Exerted on Gymnasts during Hip Beat Exercises on the Asymmetric Bars
Authors: Robertson E A , Nicol A C , Paul J P 
Published: February 2007

The study undertaken investigated the nature of the forces exerted on gymnasts due to thigh contact with the low bar during hip beat exercises on the asymmetric bars. High speed cine photography and accelerometry techniques were used to obtain the experimental data. The data from the films were analysed using a D-MAC motion analyser and computer programs. A measure of the deflection and acceleration of the low bar due to impact was obtained. A direct measure of acceleration was obtained using two accelerometer transducers attached to the low bar. The method of determining the forces from the values of acceleration is outlined and the results are presented. The implications of the findings of the study for coaches and researchers are considered and recommendations for further similar study are proffered.
Mechanical Energy Changes and the Oxygen Cost of Running
Authors: Shorten M R , Wootton S A , Williams C 
Published: February 2007

The relationship between the oxygen cost of running at submaximal speeds and running mechanics was investigated in a group of trained athletes by means of an energy analysis. Subjects were filmed while running on a motorized treadmill at speeds of 3.58, 4.02, 4.47, 4.92, 5.36, and 5.81 m/s. Segmental potential and kinetic energies were determined using a three-dimensional link-segmental model. Intra-stride changes in the energy of the whole body were computed with no allowance for energy transfer and with various energy transfer constraints imposed on the model. Oxygen consumption was determined by expired air analysis and used to estimate energy expenditure. For each transfer condition, net energy expenditure was more highly correlated with the magnitude of intra-stride energy changes than with running speed per se. The more economic running patterns were characterized by greater within-segment energy transfers. Given the limitations of the kinematic energy model, it is suggested that individual patterns of running are a significant factor in the determination of energy expenditure.
Biomechanical and Clinical Assessment of Hip Nerve Block in Unilateral Osteoarthrosis
Authors: Bader D L , Khodadadeh S , Turner A , Edmonds-Seal J , Fuller D J 
Published: February 2007

This paper combines a biomechanical analysis with a clinical assessment of eighteen patients with unilateral hip osteoarthrosis. A double blind trial was established to evaluate the potential of a regional hip nerve block in relieving pain. The characteristics of the vertical ground-reaction forces were analysed using two Kistler force plates, once before the injection and at three-monthly intervals following it. At the same time pain, mobility and functional activity were assessed clinically. A significant change in some of the gait parameters for the good leg was recorded for the total patient group one month after the injection. However, no further significant differences were found. When the symmetry of gait was evaluated no significant differences at the 1 per cent level were observed at any period. These results suggest that gait symmetry is not a significant factor in assessment of patients with hip osteoarthrosis. There was a transient decrease in subjective pain level following the injection, but this rose to pre-injection levels by the fourth week. There were no other significant general improvements after the injection. It is concluded that the biomechanical/clinical assessment has demonstrated that the hip nerve block does not provide any useful long-term pain relief.
Pressures under the Ischium Detected by a Pedobarograph
Authors: Minns R J , Sutton R A 
Published: February 2007

Pressure between the ischium and the flat surface of a pressure sensitive device (pedobarograph) are reported. There are no consistent patterns of the pressures detected this way with age, weight, sex or gross anatomy. When sitting on a gel cushion or 3 in foam cushion, the centre of load moves anteriorly and the pressures between the under surface of the cushion and the flat surface of the pedobarograph appear to be both similar and considerably lower than those pressures detected between the ischium and the flat surface. In spinal cord injured patients with pressure sores, the device indicated areas of high pressures (greater than 300 mm Hg) in the region of the pressure sores as well as a very much reduced contact area (usually less than a third) compared with normal subjects of similar weight.
Two Simple Plantar Pressure Recording Devices in Clinical Use: Evaluation Using a Pedobarograph
Authors: Minns R J 
Published: February 2007

A pedobarograph that measures and records plantar pressures has been used to evaluate the possibility of using ‘Shutrak’ as a system to measure pressures under the foot clinically. The Shutrak system is sensitive to pressures of approximately 2.5 kPa, however because of the method of loading, the record cannot be used reliably for standing pressures but can show areas of cumulative contact pressures above 2.5 kPa. Individual areas of high pressure cannot be reliably detected by this system, differentiation between light and dark areas of contact are not discernible, except where the pressures exceed 100 kPa. Plastazote depth impressions have a better sensitivity but care in heating and applying the load is necessary because of the mechanical and thermal characteristics of the material. If these are standardized, Plastozote could be used to quantify areas of high pressure as well as foot shape, but care has to be taken in interpreting data by this method. Both devices used in conjunction with a clinical examination would provide dynamic and static plantar pressure data for diagnostic use and plantar pathology investigation.
Reliability of Dynamometry in Patients with a Neuromuscular Disorder
Authors: de Boer A , Boukes R J , Sterk J C 
Published: February 2007

The reliability of a measuring method and a dynamometer itself was tested by measuring the maximal torques generated by the flexors and extensors of the elbow in healthy subjects. A similar measuring method on the same dynamometer was also studied in a group of patients suffering from a neuromuscular disorder. The healthy subjects aged twenty-one to thirty-five years were measured once a week over a period of six weeks and the patients aged twenty-three to fifty-six years once a month over a period of six months. Each measurement consisted of three registrations of three seconds. The maximal registration was taken as the measured value. The measured values of the patients show relatively large variations compared to the measured values of the healthy subjects. Analysis of the dynamometer shows problems typical for the group of patients studied. A new type of dynamometer is proposed.
Biomechanics of the Patello-Femoral Joint. Part II: A Study of the Effect of Simulated Femoro-Tibial Varus Deformity on the Congruity of the Patello-Femoral Compartment and Movement of the Patella
Authors: Fujikawa K , Seedhom B B , Wright V 
Published: February 2007

This paper investigates the effect of different degrees of varus deformity on the pattern of contact, congruence of the patello-femoral joint, and movement of the patella. Varus deformity of 5, 10, and 15 degrees was imposed on the same cadaveric knee specimen used in the study reported in Part I (Fujikawa, Seedhom, Wright, 1983). This was done by high tibial osteotomy and the introduction of a wooden wedge of the appropriate thickness to effect the deformity. It was found that the contact gradually shifted to the medial side of the knee, and the congruence of the patello-femoral compartment was gradually destroyed as the degree of varus deformity increased to 15 degrees, although the effect of 5 degrees of varus deformity was minimal. Clinically, contact is shifted to the lateral side of the knee with varus deformity, but this is invariably associated with lateral tibial rotation. This rotation explains the difference between the results of the varus deformity imposed on cadaveric knees and those observed clinically. It is proposed that an adverse change in the congruence of the knee will occur after a sudden correction by high tibial osteotomy, just as that occurring in the normal cadaveric knee after imposing a sudden varus deformity, and therefore it may be useful to consider performing the correction at an early stage of the deformity. The effect of the varus deformity on the movement of the patella is also described.
A Study of the Wear Characteristics of Sliding Pairs of High Density Polycrystalline Aluminium Oxide with Particular Reference to Their Use in Total Replacement Human Joints
Authors: Wallbridge N , Dowson D , Roberts E W 
Published: February 2007

The introduction of ceramic components into total replacement joints for the human body in the last decade has attracted considerable attention. In most cases in which a ceramic component is used a ceramic femoral head is located on a metallic femoral stem, whilst the acetabular cup is made from ultra high molecular weight polyethylene. In some designs a ceramic acetabular cup is used in association with the ceramic femoral head. A study of the basic wear characteristics of sliding pairs of high density polycrystalline ceramics is reported in this paper. Tests have been carried out under both ‘dry’ and ‘wet’ (distilled water) conditions in a tri-pin-on-disc wear testing machine. It is shown that sliding pairs of alumina ceramics exhibit remarkably low wear under dry conditions when subjected to small loads, but that high loads lead to rapid deterioration of the interacting surfaces and the onset of very high wear rates. The presence of distilled water generally permits smooth sliding at higher loads than are possible under dry conditions, but the wear rate increases by a factor of about ten over those encountered at low loads in air. The slight advantage of sliding pairs of alumina over high density polyethylene sliding on stainless steel as far as wear is concerned is not evident if the comparison is made with high density polyethylene sliding on high density ceramic in the presence of distilled water.