bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Measurement of Rotatory and Translatory Instability of the Knee Joint
Authors: Nielsen S , Hvid I , Andersen K
Published: February 2007

In the evaluation and treatment of knee ligament injuries and for comprehensive understanding of knee ligament function, it is important to know where in the movement of extension-flexion the different types of instability released by wellknown ligament injuries occur. An apparatus was developed to record anterior– posterior tibial displacement, valgus–varus instability, and axial tibial rotation instability on knee preparations, continuously, in the extension–flexion movement, when the tibia was submitted to a well-defined constant torque or force. Osteoligamentous knee preparations were suspended in the femur and a lever was fixed to the tibial segment. The lever was fitted with strain gauges to measure the torque in three planes. Potentiometers recording extension–flexion, anterior–posterior tibial displacement, valgus–varus, and axial rotation angulations were mounted. The lever was moved manually, and signals from strain gauges and potentiometers passed through an amplifier and a data acquisition system to a microcomputer, which stored the results of the measurements. The final movement curves were calculated and plotted at a regional computer service centre. Tests for reproducibility of measurements at different ligament status demonstrated a high level of reproducibility.
A New Equipment to Measure the Viscoelastic Properties of Soft Materials and its Application to Articular Cartilage
Authors: Tomita Yutaka
Published: February 2007

A new equipment to measure the viscoelastic properties of soft materials has been developed. The equipment has an advantage; the measurement of an acceleration and a collision velocity convey enough information to calculate a load and a deformation history of a specimen. The new equipment is applied to measure viscoelastic properties of articular cartilages. The specimens were taken from the proximal head of the avian tibia. In the first phase of the experiment, the specimens were filled with intercellular fluid. In the second phase, the intercellular fluid was partly exchanged with normal saline solution. The following results were obtained: (1) The collision between the impactor and the articular cartilage is not perfectly elastic, and energy is dissipated; (2) The dissipated energy is proportional to the square of the collision velocities; (3) No significant difference between the amounts of dissipated energy in the articular cartilages with the intercellular fluid and those with the normal saline solution was observed. The maximum displacement of the articular cartilages with the intercellular fluid is, however, smaller than those with the normal saline solution; (4) Intercellular fluid has the properties of a spring; (5) The articular cartilages can be approximated with a Kelvin model whose constants vary exponentially with depth; (6) The physical properties of intercellular fluid largely contribute to the physical properties of the articular cartilages.
A Description of a Versatile Microcomputer-Based System for the Clinical Measurement of Hand Strength
Authors: Carus D A , Hennedy J , Jain A S
Published: February 2007

Hand strength may be adversely affected by many conditions. Those involved in the treatment of hand disorders require an objective means of measuring hand strength, in order to monitor the progress of individual patients and to assess the value of particular treatment regimes. This paper describes the rationale behind the development of a versatile microcomputer based system for the clinical measurement of hand strength, its operation, and its uses.
Evaluation of Oral Water Irrigation Devices
Authors: Reddy Narender P , Kesavan Sunil K , Costarella Bruce R
Published: February 2007

Water irrigation devices (WIDs) are widely used in homes and dental offices across the country for oral hygiene. There have been several reported cases of tissue damage with the use of these devices. In the present investigation, two commercially available oral water irrigation devices were evaluated using bioengineering principles. The flow rates delivered by these devices were measured at different control settings. The exit jet velocities and the jet impact thrust were subsequently calculated. Both of the tested commercial oral water irrigation devices were found to exert abnormally high thrust which could cause serious damage to the sulcular epithelium and the underlying tissues. These pressures are far in excess of the pressure intensity necessary to perform the cleaning action. Moreover, the existing designs using reciprocating pumps are unsafe and are potentially dangerous, particularly with small diameter tips. Low operating pressures and the use of centrifugal pumps are recommended.
Theoretical Determination of Damage Risk Criteria for Impulse Noise
Authors: Chatham Robina
Published: February 2007

It is widely accepted that for continuous noise, a relationship exists between the energy of sound (A-weighted) and its deleterious effects on hearing. However, when the exposure is to high intensity short duration impact or impulse noise, a hitherto unpredictable degree of damage can occur to the inner ear. The present study has set out to establish damage risk criteria for a variety of impulsive waveforms.

A mathematical model of the auditory periphery has been developed and verified for sinusoidal stimulation using existing experimental data. Experimental results, obtained using guinea pigs under impulsive stimulation, were used to calibrate the model. Once calibrated the model was used to give information as to the damage likely to occur from other types of impulsive stimuli, hence reducing the need for extensive animal experimentation.

It has been shown that the model can predict the potential auditory hazard from various impulsive stimuli, quantitatively in the guinea pig and qualitatively in man. Both the experimental and theoretical results indicated that the intensity of the first pressure wave of an impulse, above a certain value, is the most significant determinator of hearing damage.

The machine designer thus has guide lines as to where to concentrate his efforts in reducing potentially traumatic machine noise.
The Design and Development of an Irrigating Sucking Cutter for Neurosurgical Use
Authors: Frost R B , Bleasel K F
Published: February 2007

The design requirements, philosophy, and decisions are described for a new surgical instrument for the removal of tough, deeply-located tumours. Prototype development and surgical experience are described.
The Effects of Hip Prosthesis Stem Cross-Sectional Profile on the Stresses Induced in Bone Cement
Authors: Orr J F , James W V , Bahrani A S
Published: February 2007

Bone cement has often been regarded as a weak link in a joint replacement structure. In spite of this, there has been little work published concerning experimental analysis of stresses in the cement. The purpose of the experiments described in this paper was to study the effects of some hip prosthesis stem designs on stresses in bone cement. The opportunity was also taken to examine some hypothetical designs. Photoelastic results show that some current designs of prosthesis stems cause less stress concentrations in cement than former designs. Stem designs which appeared good from photoelastic considerations also performed well in mechanical tests involving the impression of stem profiles in bone cement. A modification to current prosthesis stems is proposed which improves the ability of the cement to resist deformation.
Computer Aided X-Ray Picture Follow-up of GSB Knee Prostheses
Authors: Munzinger U , Gschwend N , Scheier H , Frey O , Wysss U
Published: February 2007

The data relating to 155 patients reviewed at the Wilhelm Schulthess Clinic in Zurich (clinic of the originators of the GSB knee prosthesis) have been evaluated in the present study. The X-ray pictures of the patients with implanted GSB knee prostheses were studied up to ten years at 1–2 years' intervals on the basis of 45 characteristic dimensions. The 15000 measurements of the study have been evaluated by means of a computer. The paper describes the method used and reports the statistical results obtained.
Conference Report: The Biomechanics of Osteoarthrosis
Authors: Wright V
Published: February 2007

Organised by The Bioengineering Group for the Study of Human Joints, University of Leeds, In Association with The Biological Engineering Society.
An Analysis of the Stresses in a Thin Layer of Articular Cartilage in a Synovial Joint
Authors: Armstrong C G
Published: February 2007

The stresses to which articular cartilage is subjected during its normal function undoubtedly influence its useful life. A simple yet rigorous approximate analysis of cartilage loading has been developed which allows cartilage stresses, strains and deformations to be determined from the thickness and material properties of the cartilage and its surface loading. Using this analysis to examine the probability of cartilage failure suggests that the pressure gradients and distribution in a joint are probably as important as the absolute values of pressure. The analysis also helps to explain certain characteristics of the cartilage and certain types of cartilage failure.
Experimental Arthrosis by Hyperpressure
Authors: Bejui J , Harmand M F , Duphil R , Roussouly P , Comtet J J , Anania G
Published: February 2007

The frequent occurrence of degenerative joint disease (DJD) pathology and the high degree of functional prejudice associated with it, justify the search for experimental models with a view to a better understanding of this pathology and its treatment. The models most commonly used resort to a sudden mechanical degradation by shock (post-contusive osteoarthritis) or to a kinematic disruption of the joint through more or less extensive menisco-capsulo-ligamentary lesions or lesions induced by toxic substances.

Cartilaginous lesions met with in human pathology are often secondary to a morphological anomaly at the origin of a hyperpressure. Maquet (1977) has suggested the bringing forward of the anterior tibial tubercle (ATT) in order to reduce the retro-patellar pressure. The drawing back by hollowing of this ATT appeared to us a suitable model for experimental osteoarthritis by hyperpressure.
Remodelling of Trabecular Bone at the Proximal Tibia after Total Knee Replacement. A CT-Scan Study
Authors: Hvid Ivan , Bentzen Soren M , Jorgensen Jorgen
Published: February 2007

Five patients were examined by quantitative computed X-ray tomography of the proximal tibia immediately after total knee joint replacement, and examinations were repeated after 6 to 26 months. The relative attenuation coefficient derived from the digital images was transformed to compressive yield strength according to earlier work (Bentzen et al., 1985a). Significant deviations from the normal distribution of bone strength were noted at the first examination with high strength medially in varus knees and laterally in valgus knees, and low bone strength at the unloaded condyle. After six months these abnormalities had changed towards a more normal pattern, bone strength being reduced where it had been high at the time of operation and slightly increased where it had been low. One tibia showed no signs of remodelling.
Biomechanical Compatibility of Cruciate Ligament Prostheses
Authors: Cooke P H , Goodship A E
Published: February 2007

An experiment was performed to determine the effects of stiffness of cruciate ligament prostheses upon joint function and degeneration. Twenty four sheep were allocated into four groups. One group had the ligament excised with no replacement and subsequent groups underwent substitution procedures with either a stiff, matched, or lax prosthesis. After six months the animals with a stiff or matched prosthesis were significantly less lame than those with a lax prosthesis or no prosthesis. However, at post mortem examination the animals with a stiff prosthesis or no prosthesis showed significantly more widespread cartilage damage than the matched or lax groups. The results indicate that either a stiff or matched prosthesis may restore functional activity, but that the stiff prosthesis may predispose to increased degenerative changes.
The Use of Spectral Analysis to Assess the Performance of Shock Absorbing Footwear
Authors: Johnson G R
Published: February 2007

Spectral analysis methods have been used to examine the influence of shock absorbing inserts on heel strike transients in normal gait. The data were obtained from a piezoelectric accelerometer mounted on a custom moulded splint fitting around the malleoli which was found to eliminate unwanted resonances. The peak accelerations measured with this system were similar to those obtained in earlier studies. Examination of the gait of one subject in four different types of footwear showed that a reduction of rms acceleration could be achieved by the use of a shock absorbing insert. The efficiency of the insert was measured by its ability to reduce the rms acceleration in the 10–150 Hz band and to reduce the rms signal in the 50–150 Hz band as a proportion of the total. This second measure was defined as the ‘Shock Factor’.
A Stereotaxic Device for the Closed Exchange of Intramedullary Rods, Using Image-Intensified X-Rays, in Children with Osteogenesis Imperfecta
Authors: Frost R B , Middleton R W D , Hillier L G G
Published: February 2007

The necessity for such a device, its concept and realisation are described, together with some impressions formed during its use in surgery.
Determination of the Transverse Centre of Rotation of the Knee Using CAT Scans
Authors: Brunet Michael E , Kester Mark A , Cook Stephen D , Haddad Ray J , Skinner Harry B
Published: February 2007

Digitized serial CAT scans of four non-embalmed cadaver knees were used in the computer-aided determination of the longitudinal (internal-external) centres of rotation. The mean and standard deviation of the centre of rotation locations were calculated both before and after sectioning the anterior cruciate ligament. Regardless of anterior cruciate ligament status, the mean location of the centre of rotation was on the tibial spine, slightly anterior to the origin of the posterior cruciate ligament. However, upon sectioning of the anterior cruciate ligament, the standard deviation of the centre of rotation location increased markedly in the latero-medial direction in three of the four legs tested.
Power Law Models for the Mechanical Properties of Cancellous Bone
Authors: Currey J D
Published: February 2007

This note is a discussion of the merits or otherwise of using linear rather than power law regression models in some biomechanical analyses.
The DHSS Evaluation Programme for Infusion Control Instruments
Authors: Auty B
Published: February 2007

The DHSS commissioned the Bath Institute of Medical Engineering (BIME) to carry out a comparative evaluation of instruments for the control of intravenous infusions. This project commenced six years ago. To date, six reports have been published in the DHSS‘ Health Equipment Information series and more are in preparation. Some three dozen different instruments have been assessed.

The programme proceeds in three independent phases: technical, clinical, and safety testing. The technical phase includes performance testing in the laboratory, assessment of ease of operation and assessment of design and production techniques used, ease of servicing, and reliability.

The clinical evaluation is designed to check the capability of the instrumentation under actual ward usage and questionnaires are completed by medical staff.

Safety testing to BS 5724 Part 1 is undertaken at the British Standards Test House at Hemel Hempstead.

There are four different types of instrument for infusion control: gravity controllers, drip-rate pumps, volumetric pumps, and syringe pumps. Each type has different performance characteristics to cater for specific applications.

During the course of the evaluation, much has been learnt and many different aspects of performance have been studied, including drop size variations, air embolism, delivery pressure, and alarm response times.
Site-Specific Drug Carriers
Authors: Tomlinson E
Published: February 2007

Site-specific drug carriers are required to exclusively deliver drug molecules to difficult targets within the body. They should do so in a form which protects the drug and host from one another. This contribution reviews the reasons for drug targeting, and describes some of the features required of two types of carrier system, i.e., particulates and soluble (bio)conjugates.
Body Surface Measurement and Replication by Photogrammetry and Computer Aided Design
Authors: Vergeest Joris S M , Broek Johan J , Van Voorden A
Published: February 2007

This article presents and demonstrates a method of measuring the shape of the human skin and of reproducing the form as a real three-dimensional object at any scale. The working system consists of two parts, each normally in use for different disciplines at Delft University of Technology. The two parts, that we have interfaced, are a photogrammetric stereo restitution system and a CAD system integrated with a numerically controlled 3D milling machine.

One stereopicture of (an arbitrary part of) the human body is sufficient to obtain any number of digitized points of the visible surface. Our system does not necessarily rely on reference grids, calibration frames, or surface marking points. Repeated measurements have shown that a measurement precision of 0.06 per cent of the observation distance is achieved. The data allow a complete surface representation by the CAD system, which in turn provides facilities for fast interactive viewing, for high quality colour image generation, and reproduction of the shape in foam material.
Quantitative Approach to Osteoarthritic Gait Assessment
Authors: Khodadadeh Soussan
Published: February 2007

Measurements of the gait of 42 patients with osteoarthritis of the hip are made using only a pair of small force plates with computer interfacing. The use of more complex and expensive television systems is thus avoided.

The force between the foot and plate is measured during gait, resolved into vertical, horizontal, and lateral force components, and graphs of the time variations of these components produced. It is shown that an accurate on-line assessment of pre- and post-operative gait can be made, but only by reference to all three force component curves.

A numerical assessment of the gait condition is obtained as the total of scores for clearly identified separate features of each curve. This helps the clinician to arrive at a firm value and should reduce subjective variations arising from attempts to assign a single overall number for the ‘quality’ of each curve.
Indentation Study of the Biomechanical Properties of Articular Cartilage in the Canine Knee
Authors: Jurvelin J , Kiviranta I , Arokoski J , Tammi M , Helminen H J
Published: February 2007

Considering articular cartilage to be composed of an elastic organic matrix and interstitial water, compressional stiffness of canine knee (stifle) joint cartilage was determined in the form of shear moduli. Different stresses and indenters were used to reveal the suitability of the indentation measurement with a step-load. We were able to demonstrate the linearity of instant and equilibrium responses of cartilage. Using a theoretical solution for indentation of an elastic layer, the effect of the finite thickness of cartilage on the instant and equilibrium responses was eliminated. Using the intrinsic (equilibrium) shear modulus of the cartilage matrix, the stiffest cartilage was found to be located in the patellar surface of the femur. The thick, proteoglycan-rich tibial cartilage, which was uncovered by menisci, was softer than the opposing femoral cartilage. This finding casts doubt on the suggestion that the concentration of proteoglycans unambiguously determines the stiffness of cartilage, but emphasizes the importance of the collagen network also in the compressional behaviour of the cartilage.
An Automated Technique for in Vitro Assessment of the Susceptibility of Urinary Catheter Materials to Encrustation
Authors: Cox A J , Hukins D W L , Davies K E , Irlam J C , Sutton T M
Published: February 2007

An automated technique has been developed for assessing the extent to which existing or potential materials for the construction of indwelling catheters become encrusted during exposure to infected urine. In this technique the enzyme urease is added to artificial urine containing albumin in a reaction vessel which contains the samples to be tested. Controlled replacement of reactants leads to appreciable formation of encrusting deposits which adhere firmly to the surface of the test samples. Deposits have the same chemical composition as those which encrust catheters in vivo.
Perspectives in Non-Traditional Biofluid Mechanics
Authors: Reddy Narender P , Kesavan Sunil K
Published: February 2007

Although biofluid mechanics has been studied extensively, most of the studies have concentrated on cardiovascular biofluid mechanics. Very little attention has been paid to the other important problems in biomedicine. Several non-traditional areas which offer interesting and challenging problems remain unexplored, and fluid mechanics can have fruitful interaction with these disciplines. This paper brings into focus some of the important areas of biomedicine which offer fertile grounds for biofluid mechanics studies.
Hydrodynamic Advantages and Disadvantages of Mechanical Bileaflet Valves and Tilting Disc Valves No. 29
Authors: Heiliger R
Published: February 2007

In order to determine the effectiveness of mechanical heart valves two different types of mechanical heart valves, three tilting disc valves (BS–SD, BS–CCD, BS–M) and two bileaflet valves (St Jude Medical, Duromedics) with the same size of annulus diameter dA = 29 mm have been investigated in the mitral position of a mock circulation under pulsatile flow conditions. Flow, pressure and orifice area have been measured. Insufficiency, mean orifice area, discharge coefficient, performance index, and efficiency index have been calculated.

The investigated tilting disc valves show smaller reflux volume and smaller insufficiency when comparing with the bileaflet valves. The bileaflet valves show higher values of orifice areas—that is to say smaller pressure drops—than the tilting disc valves. The St Jude Medical shows the biggest orifice areas, but also the highest reflux volume and insufficiency. Insufficiency of the Duromedics is slightly higher than that of the tilting disc valves. The orifice area of the Duromedics is bigger than that of the tilting disc valves and smaller than that of the St Jude Medical. The different pivot and the different profile of the disc of the BS–CCD and the BS–M are responsible for the more constant behaviour of the opening of these tilting disc valves when comparing with the BS–SD. Though the bileaflet valves show the better efficiency index, none of the valve types is superior in all hydrodynamic criteria. Both valve types, the bileaflet valves and the tilting disc valves, show different hydrodynamic advantages and disadvantages.
The in Vivo Durability of Bioprosthetic Heart Valves-Modes of Failure Observed in Explanted Valves
Authors: Lawford P V , Black M M , Drury P J , Roberts K , Bilton G
Published: February 2007

This paper describes the results of a detailed investigation of 59 explanted bioprosthetic heart valves. The mean time of implantation was 5 years 9 months with 84 per cent of the valves implanted for more than 2 years 6 months. Valves were subjected to gross examination, radiography, and hydrodynamic testing prior to dissection and histological studies in order to establish the primary cause of failure or dysfunction. Typical failure modes were determined for the major types of bioprosthesis studied. The factors influencing bioprosthetic valve dysfunction are discussed.
Pericardial Heterografts: A Method for Leaflet Mechanical Property Control
Authors: Trowbridge E A , Crofts C E
Published: February 2007

Glutaraldehyde fixation of bovine pericardium produces a material which is more extensible than the natural tissue. Chemically modified pericardial sacs from 16–20 week old calves provide a region 12 000 mm2 in area which has relatively uniform properties. Tricuspid heterografts constructed from this material have maximal bending stresses at two sites associated with valve failure through mechanical tissue fatigue.
The Use of Ceramics in Prosthetic Heart Valves
Authors: Gentle C R
Published: February 2007

A survey is carried out of how various ceramics have been used or considered as materials for prosthetic heartvalves. The ceramics include pyrolitic carbon, titanium dioxide, porous and fully dense alumina, and single crystal alumina. Particular attention is paid to the ability of some types of alumina to support a stable tissue covering which then camouflages them from further interactions with the blood.
Mathematical Models of Musculoskeletal Systems
Authors: Calderale P M , Scelfo G
Published: February 2007

An understanding of the forces which act in the musculo-skeletal system is required in a number of applications. This study provides a critical and comparative discussion of the methods used to determine the muscle and joint forces, and presents an analysis of future prospects for applying these methods.
A Leg Positioning and Holding Mechanism for Use during Knee Surgery
Authors: Churches A E , Walsh M J , Fisher W E , Anderson J B
Published: February 2007

The paper describes a novel leg positioning and support mechanism for use during knee surgery. The limb is positioned by controlling hip flexion–extension and hip abduction–adduction, using the normal thigh tourniquet as an attachment point for the mechanism. The knee joint and the lower leg are not impeded by the device and the surgeon may freely test knee joint movements.

Early experience in the operating theatre indicates significant advantages in freeing the assistant surgeon for other duties, reduced physical effort, and firmer retention of the leg. The use of the leg positioning and support mechanism may permit ergonomically improved operating techniques to be developed.
Force Plate Studies of Duchenne Muscular Dystrophy
Authors: Khodadadeh S , Mcclelland M , Patrick J H
Published: February 2007

Changes in the pattern of force plate measurements between the first and second peak have been shown to reflect pathological gait. However, analysis of such force plate readings for boys with muscular dystrophy fails to show any significant variation in the vertical loading pattern when compared to normal boys.
The Measurement of Stiffness in the Rheumatoid Hand
Authors: Helliwell P S , Howe A , Wright V
Published: February 2007

Previous attempts to measure stiffness objectively are reviewed. A major limitation of the earlier studies using arthrographs is the lack of definition of the equilibrium position of the joint. Other devices which claim to measure stiffness indirectly also fail to define this characteristic of the joint, and this omission may cause misleading results. We have measured stiffness in 135 patients with rheumatoid arthritis (RA) and have compared this group with 128 normal subjects. In addition we have measured stiffness over a 24 hour period in a further 14 subjects with RA. Mean values for resistive torque were 72.9 Nm. per degree in RA and 81.6 Nm. per degree in normals (Ns), for hysteresis 32.6 per cent in RA and 36 per cent in normals ( P < 0.001), and for equilibrium position 5.6 degrees ulnar deviation in RA and 3.2 degrees ulnar deviation in normals ( P < 0.001). The difference in hysteresis values is probably due to the muscular wasting consequent on chronic RA. Stiffness variables did not show evidence of circadian variation, but there was evidence of a change in equilibrium position into ulnar deviation in the early hours of the morning. The symptom of early morning stiffness may well be due to this change in equilibrium position coupled with muscular factors and fluctuations in pain intensity.
Assessment of a New Hip Dynamometer
Authors: Greena J , Mckenna F , Ellis M , Helliwell P , Howe A , Chamberlain M A
Published: February 2007

A new system for measuring power and endurance of muscles around the hip joint is described. The system is designed to be used in a study involving patients with osteoarthritis of the hip joint.

The system is compared with previous work in this field.

The method of use and a study to evaluate reproducibility are described. Ten patients with osteoarthritis of the hip joint, and eleven volunteers were tested. Results show reasonable levels of reproducibility for power; endurance was less reproducible.
A Clinical Gait Analysis System
Authors: Ellis Malcolm , Howe Adrian
Published: February 2007

A gait analysis system has been devised that is not only relatively inexpensive, but is also quick to use, requires no expertise to run, and does not need any special laboratory facilities.

The system monitors the subject's knee and hip movements during ambulation using electro-goniometers. Foot contact data are obtained using lightweight, flexible, foot switches. The data are sent to a computer via an eight channel telemetry system carried by the subject on a waist belt.

The software is designed to simplify analysis and be ‘user friendly’. After a simple calibration routine, the system prompts the operator to ask the subject to walk a number of steps. The computer ignores the initial steps taken as these are not typical of normal gait. It then collects data from the consequent steps, averages the data and then displays them in both graphical and numerical form. A patient can be tested and a printout provided for insertion in the patient's notes within ten minutes.

Only one hours training is required to learn to operate the system. A patient can be tested in a physiotherapy department, corridor, or in any area where a few consecutive steps can be taken.
The Role of Gait Analysis in Clinical Medicine: A Survey of UK Centres
Authors: Messenger N , Bowker P
Published: February 2007

This paper reports the results of a survey carried out to assess the clinical usage currently being made of gait analysis facilities within the UK.

Thirty-five centres were circulated with a questionnaire which requested information under four main headings: (i) equipment, (ii) research projects, (iii) clinical service commitments, and (iv) subjective views of the ultimate clinical value of the service. Of the 25 completed questionnaires returned, 16 were suitable for inclusion in the final analysis of data.

The survey provided useful data on the equipment and facilities available in each centre together with details of the service available to prospective referring clinicians. Ten centres were considered as being currently involved in some clinical work, with six of these being routinely involved.

The respondents generally felt that gait analysis techniques have a clinical context, if not yet routinely, but the numbers of referrals to the centres is still quite small. A number of areas worthy of further work were identified by the respondents. It is hoped that presentation of these results will stimulate dialogue between centres and between clinicians and bioengineers.
The Measurement of Stiffness of Fractures Treated with External Fixation
Authors: Cunningham J L , Evans M , Harris J D , Kenwright J
Published: February 2007

A method for the measurement of the mechanical stiffness of fractures treated with unilateral external skeletal fixation is described. The procedure for obtaining fracture stiffness results is detailed, and results showing three distinct patterns of healing, which can be related to in vivo biological events, are presented.
The Ratio of Upper Lumbar to Lower Lumbar Sagittal Mobility Related to Age, Sex, and Low Back Trouble
Authors: Burton A Kim
Published: February 2007

A simple clinical technique, utilising a modified flexicurve, has been used to measure sagittal mobility in upper and lower regions of the lumbar spine in 624 subjects. The results confirm that mobility is related to age, sex, and current low back trouble, but also reveal a relationship with a history of previous complaints. The ratio of upper to lower mobility does not show a predicted pattern of increase in the presence of degenerative change or current back trouble compared with young or symptomless subjects, but rather suggests that the reduction of mobility in symptomatic back trouble may be effected by non-articular factors. The wide range of upper/lower ratio found here deserves further exploration but indicates potential clinical value for the flexicurve technique.
Measurement of Flexural and Torsional Stiffness for the Human Torso in Vivo; Implications for Scoliosis
Authors: Smeathers J E
Published: February 2007

Voluntary oscillations of the human torso are analysed using engineering beam theory to estimate the flexural and torsional stiffness of the back. Antero-posterior and lateral flexural stiffness are measured as well as the torsional stiffness for both relaxed conditions and at maximum voluntary exertion. The ratio of flexural stiffness in two mutually perpendicular planes is a guide to the torsional stability of a beam in bending. These criteria are used to assess the torsional stability of the human torso when subjected to large bending moments.
Radiographic Determination of the Angle of Version of the Femoral Component in Total Hip Replacement
Authors: Schmotzer Hans , Learmonth Ian D
Published: February 2007

This paper describes a simple method to determine stem orientation after total hip replacement. It is based on standard antero-posterior radiographs and computes the angle between prosthesis and film plane from the shortening of predefined distances in the projection.

The error of the method is less than 5 per cent for the stem orientation and less than 10 per cent for the neck orientation. The method allows accurate control of stem orientation by means of standard equipment in orthopaedic practice.
Theoretical Analysis of Fracture Healing Monitoring with External Fixators
Authors: An Kai-Nan , Kasman R. A. , Chao Edmund Y. S.
Published: February 2007

A fracture healing monitoring system with external fixators was analysed using the finite element method. Pin displacement and side bar strain under axial and side loading were evaluated at various stages of simulated fracture healing. In general, a recovery of rigidity at the fracture site of up of 25 percent of intact bone could be sensitively predicted. Effects of cross-sectional distribution and length of callus at the fracture site on pin displacement and side bar strain were studied. Alterations of fixation configuration, such as component failure during the healing process, were found to have relatively little effect on pin displacement but a rather larger effect on side bar strain. In general, the assessment of fracture healing by monitoring the deformation of external fixation devices is a useful idea. However, in practice, great care must be taken to fully understand the implication of the monitoring system before drawing conclusions on such measurements.
Computerized Cheirometer for Assessing Grip-Strength Indices and Classification of Rheumatoid Patients
Authors: Chan Alfred P K , Kamath Markad V , Buchanan W Watson , Ghista Dhanjoo N , Grace Eileen M , Anvari Payman
Published: February 2007

A computerized Cheirometer has been developed to objectively assess grip strength indices (GSI) of normals and rheumatoid arthritis (RA) patients. The instrument consists of a hand-grip bladder, an LVDT pressure transducer (Schaevitz) interfaced through a 12 bit A/D converter to an Apple II + computer. Software has been developed for data acquisition, display and classification of measured GSI into moderately diseased and severely diseased and normal classes.

During the developmental phase of the instrument, it was noted that maximum pressure ( PM) and rate-of-rise (ROR) of pressure during the squeezing of the bladder were the most sensitive indices to distinguish and classify normal and patient hand-grip waveforms. The reproducibility of PM and ROR as useful GS indices was tested in 13 chronic RA patients in the morning, with two measurements per patient, within half-hour intervals. The results indicate that PM and ROR are stable indices with no significant variation between two measurements ( p < 0.05). A Bayes classifier program was developed to recognize and classify normal and pathological signatures of grip strength. The classifier accuracy was evaluated in 79 patients in the Rheumatology clinic at McMaster Hospital. A classification accuracy of 90 per cent was obtained in classifying normals and pathological subjects.
On the Mechanical Function of Marrow in Long Bones
Authors: Bryant J D
Published: February 2007

Hydraulic strengthening, viscous interaction between marrow and trabecular bone, and viscous resistance by the marrow to shear, appear not to occur in long bones when subjected to non-destructive axially applied compressive loads. These conclusions are based on the following observations.

Firstly, volumetric measurements suggest that long bones deform in a way that maintains a near constant volume. Hence the mechanism by which ‘hydraulic strengthening’ could operate seems not to exist.

Secondly, with little or no volume change, no significant movement between the marrow and the adjacent trabecular bone is likely to occur. The only mechanism by which the marrow could function mechanically would be by its own viscous resistance to shear deformation. As marrow is near liquid at 37°C (with a measured viscosity of 67 × 10-3 Pa s) this ‘resistance’ is shown to be negligible, even when calculated using values most favourable to the production of large shear forces.
Can the Weight-Bearing Capacity of the Femoral Neck be Estimated by Physical Measurements on the Greater Trochanter?
Authors: Leichter I , Simkin A , Margulies J Y , Bivas A , Roman I , Deutsch D , Weinreb A
Published: February 2007

Early detection of mechanical weakening of the femoral neck would help to prevent fractures at this site which are the most serious clinical problem in osteoporosis. In the vicinity of the femoral neck, the greater trochanter is a superficial bone structure more easily accessible to in vivo measurements. The purpose of the present study was to evaluate the relation between the strength of the femoral neck and the composition of the trabecular tissue in the greater trochanter. Twenty-nine fresh human intact femora were examined. The relationship between the average shear stress in failure of the femoral neck (ASS) and the Ca concentration (CC), mineral density (BMD), and overall mass density (BD) of the greater trochanter was investigated. Linear stepwise regression analysis showed that the ASS of the femoral neck can be predicted from the BD, CC, and BMD of the trochanteric tissue, and their contribution to the estimation of the ASS was ranked in the above order. The linear function relating the ASS to these variables showed a highly significant multiple correlation ( R = 0.87, p < 0.001). Therefore in vivo measurements of the density and mineral content in the greater trochanter should be considered useful in assessing the risk of fracture of the femoral neck.
A Comparative Evaluation of Modern Fracture Casting Materials
Authors: Martin P J , Weimann D H , Orrxy J F , Bahranixys A S
Published: February 2007

This paper reports on a comparative investigation into the mechanical and handling properties of a selection of currently marketed bandage-form casting materials. The aim of the investigation was to develop a quantitative evaluation of available materials for use in the particular application of femoral fracture bracing. A field survey of Northern Ireland hospitals was conducted which showed that certain handling properties were important to those actually using the materials. A series of engineering and handling tests were developed on the basis of the replies received and executed on each of the materials. It was found that all the modern synthetic casting materials performed better than plaster of Paris. The findings of the investigation and the results of the field survey will be of interest to anyone involved in the application of the new materials and also to those manufacturing them.
Strength Pattern of Cancellous Bone at the Ankle Joint
Authors: Jensen Niels Christian , Hvid Ivan , Krøner Karsten
Published: February 2007

The strength pattern of cancellous bone was examined in 17 ankles by a cylinder compression test and in eight distal tibial specimens by an osteopenetration test.

With the compression test, 6 mm levels were examined, five levels at the tibia and three levels at the talus. Cylinders were obtained from all levels from corresponding locations. The cylinders were tested at a constant deformation rate of 5 mm/min until failure. From the load deformation curves ultimate strength, yield strength, yield strain, ultimate strain and elastic modulus were calculated.

The penetration test involves resection of the joint surface just above the subchondral bone plate at the distal tibia. Measuring force and displacement, a 2.5 mm conical needle was pushed into the bone at 25 locations in a 5 × 5 matrix. The force-displacement curves were integrated at intervals of 2 mm. Three levels were evaluated, corresponding approximately to the first level in the compression test.

The study indicates the presence of a strong antero-lateral part and a slightly weaker postero-medial part at all levels in the tibial and talar bone. The compression test at level 1 and the penetration test at levels 1, 2, and 3 in the distal tibia revealed a high strength area crossing the central part, in contrast to the proximal levels of the tibia where the central parts were very weak. At the talus, a high strength area ran along the lateral and posterior border. There were no significant differences in the profiles of ultimate strength, yield strength, and elastic modulus.
Rotational Movement of Femoral Components of Total Hip Replacements in Response to an Anteriorly Applied Load
Authors: Tanner K E , Bonfield W , Nunn D , Freeman M A R
Published: February 2007

Mechanical testing has been performed on total hip replacements implanted in sections of cadaveric femora. A purpose built transducer has been used to measure the rotation of the implant in the bone under loads applied in the anterior-posterior direction. This has been used to assess the effect of cement and also of retaining more of the femoral neck.

The retention of the femoral neck improved stability, as did the bone cement, and in the case of the uncemented prosthesis, longitudinal ridges increased the stability of the prosthesis.
Biomechanical Properties of the Canine Knee Articular Cartilage as Related to Matrix Proteoglycans and Collagen
Authors: Jurvelin J , Säämänen A-M , Arokoski J , Helminen H J , Kiviranta I , Tammi M
Published: February 2007

The instant, creep and equilibrium responses of canine knee articular cartilages were determined after a constant load application with an in situ indentation creep test and related to the chemical composition of the tissue. Instantly, the cartilage stiffness correlated inversely with the proportion of proteoglycans (PGs) extractable with guanidium chloride. The tibial cartilage, rich in PGs but relatively poor in collagen, showed a low resistance to instant rearrangement of the solid matrix after load application. However, the resistance of the tibial cartilage to water flow during creep deformation was similar or even higher than in the femur. The rate of creep correlated inversely with the PG content. The equilibrium modulus of the femoral cartilage (0.40 MPa), 29 per cent higher than in the tibia (0.31 MPa), was related to the content of PGs, while in the tibia the direct correlation between PGs and modulus was not observed. Our results suggest that while PGs control the fluid flow in articular cartilage, a high PG content alone does not guarantee high stiffness of the cartilage. Instead, the properties of the collagen network are suggested to control particularly the instant shape alterations of the articular cartilage under compression.
In Vitro Fluid Dynamics of the St Jude Valve Prosthesis in Steady and Pulsatile Flow
Authors: Hanle Daniel D , Harrison Earl C , Yoganathan Ajit P , Corcoran William H
Published: February 2007

The flow downstream from the St Jude valve prosthesis is studied in vitro in both steady and pulsatile flow. Conditions for the pulsatile flow studies approximate the in vivo resting state. Laser-Doppler anemometry (LDA) is used to measure instantaneous point velocities at numerous locations pre-selected to conform to a systematic, flow-mapping measurement methodology. Overall, the results for the St Jude valve indicate a relatively undisturbed forward flow through the prosthesis. The acceleration ratios, defined as the maximum mean axial velocity for the St Jude valve divided by that for no valve obstructing the flow, are small, being 1.2 and 1.4 for steady and pulsatile flow, respectively. Both the secondary flow structure and the flow disturbance produced by this valve are minimal. Maximum mean velocities in the radial and azimuthal directions are only about 5–10 per cent of that in the axial direction. There is, however, notable evidence of flow wakes generated by the valve's opened leaflets. Velocity defects caused by these wakes are found to be as much as 50 per cent. The bulk flow through this valve is in this sense quite unlike that reported by others for the natural aortic valve studied in vitro.
A Numerical Solution to the Elasto-Hydrodynamic Problem
Authors: Dowson D. , Higginson G. R.
Published: February 2007

This paper presents a solution to the problem of hydrodynamic lubrication of highly loaded clastic cylinders under isothermal conditions. A numerical method is developed which enables a pressure curve to be found which satisfies the elastic and hydrodynamic requirements of the system.

Results are presented which take account of elastic distortion and the dependence of viscosity upon pressure for centre-line pressures of 5, 10, 20, and 30 ton/in2. In addition solutions are given for both rigid and elastic solids when the centre-line film thickness is the same in each case.
Determination of the Viscosity of Steam at Super-Critical Pressures
Authors: Kjelland-Fosterud Einar
Published: February 2007

This paper records the measurement of the viscosity of the water substance at pressures from 200 atmospheres to 1000 atmospheres and at temperatures from 370 to 540°C. The viscometer, which is of a capillary type, uses the principle of the falling mercury pellet but is of a special design prepared by the author to meet the extreme conditions under which the observations were to be made. A careful examination has been carried out of the possible sources of error, and the necessary corrections and calibrations are given. At the lower end of the range of pressure, at which recent data are extant from other workers, the results are in close conformity with those from the existing sources.
The Vibration and Balancing of an Unbalanced Flexible Rotor
Authors: Bishop R. E. D. , Gladwell G. M. L.
Published: February 2007

The motion of a flexible unbalanced rotating shaft is examined. The effects of balancing such a shaft (as a ‘rigid body’) in a conventional low-speed balancing machine are explained. The underlying theory of a general method of balancing flexible rotors, mode by mode, is then given. The paper contains a discussion of the effects of dead weight on the deflection of a rotating shaft.
The Receptances of Uniform and Non-Uniform Rotating Shafts
Authors: Gladwell G. M. L. , Bishop R. E. D.
Published: February 2007

Expressions are found for the receptances of flexible rotating shafts. They are in series form and are expressed in terms of characteristic functions whose derivations and properties are explained. A knowledge of these receptances is all that is needed as regards the shaft in a theoretical discussion of any system of which the shaft forms part; in particular they permit the investigation of the motion at critical speeds and the stability of shafts in flexible bearings.