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Biomedical subjects

F C Wang

Publications and source records attributed to F C Wang.

At least 19 recordsLinked to original sources
PubMed2005

[How I explore. . . vasculitis of the peripheral nervous system].

Vasculitic neuropathies require early diagnosis and therapy since their prognosis is potentially severe. The following features are usually suggestive of a vasculitic neuropathy: painful multiple mononeuropathy with an acute/subacute course, signs and symptoms of multisystem involvement (arthritis, asthma, renal and skin involvement), biological evidence of an inflammatory syndrome. In one third of patients however, vasculitic neuropathies present as a polyneuropathy. For other patients, peripheral neuropathy is the presentation mode of a necrotizing vasculitis, in the absence of biological inflammatory syndrome. A combined muscle and nerve biopsy, will usually demonstrate the vasculitic process. Vasculitic neuropathies often have a favourable prognosis when immunosuppressive therapy (corticosteroids and/or cyclophosphamide) is initiated at an early stage.

Humans↗
PubMed2004

Steady-state elastohydrodynamic lubrication analysis of a metal-on-metal hip implant employing a metallic cup with an ultra-high molecular weight polyethylene backing.

The elastohydrodynamic lubrication (EHL) analysis was carried out in this study for a 28 mm diameter metal-on-metal hip prosthesis employing a metallic cup with an ultra-high molecular weight polyethylene (UHMWPE) backing under a simple steady state rotation representing the flexion/extension during walking. Both Reynolds and elasticity equations were coupled and solved numerically by the finite difference method. The elastic deformation was determined by means of the fast Fourier transform (FFT) technique using the displacement coefficients obtained from the finite element method. Excellent agreement of the predicted elastic deformation was obtained between the FFT technique and the conventional direct summation method. The number of grid points used in the lubrication analysis was found to be important in predicting accurate film thicknesses, particularly at low viscosities representative of physiological lubricants. The effect of the clearance between the femoral head and the acetabular cup on the predicted lubricant film thickness was shown to be significant, while the effect of load was found to be negligible. Overall, the UHMWPE backing was found not only to reduce the contact pressure as identified in a previous study by the authors (Liu et al., 2003) but also significantly to increase the lubricant film thickness for the 28 mm diameter metal-on-metal hip implant, as compared with a metallic mono-block cup.

Computer Simulation↗
PubMed2004

A general elastohydrodynamic lubrication analysis of artificial hip joints employing a compliant layered socket under steady state rotation.

A general numerical methodology was developed in the present study to analyse the elastohydrodynamic lubrication problem of a compliant layered socket against a rigid ball under steady state rotation representing flexion and extension during walking, with particular reference to artificial hip joint replacements. The general numerical methodology consisted of using the Newton-Raphson method to solve the Reynolds equation, simultaneously with the full elasticity equation using the finite element method in combination with the fast Fourier transform technique. Two specific types of acetabular cup were considered, one with ultra-high molecular weight polyethylene used in current total hip joint replacements, and one with polyurethane proposed for compliant layered 'cushion form bearings' for future developments. The film thickness and the pressure distribution for both cups were obtained under a wide range of operating conditions. The predicted central or average film thicknesses within the contact conjunction were compared with those estimated from various simplified theories available in the literature. A simple analytical methodology was consequently established to estimate the lubricating film thickness in a compliant layered socket, based on the corresponding ball-on-plane model and the consideration of the curvature effect.

Computer Simulation↗
PubMed2004

[Advantages and limitations of the motor unit number estimation techniques].

It is now 30 years since the first motor unit number estimation (MUNE) technique was introduced by Allan McComas as a way of providing an objective, sensitive and reproducible means of measuring the number of motor axons in living human muscle or muscle group. MUNE techniques have substantially evolved over the past decade and have been applied, with increasing frequency, to the study of age effects on motoneurone population and muscle denervating disorders such as amyotrophic lateral sclerosis (ALS), spinal muscular atrophy, poliomyelitis and different types of inherited and acquired peripheral neuropathies. In the future, one of the most important topics involving MUNE, will probably be its use in monitoring the progress of ALS patients undergoing experimental drug trials. However, among incremental, multiple point stimulation, spike-triggered averaging, F-wave analysis and statistical methods, there is no consensus about the best MUNE method. There is only a general feeling that some techniques are more valid than others. For this reason, in the present review, brief descriptions of the distinct MUNE methods are presented. In the second part of the paper, advantages and limitations (alternation, sampling errors, temporal registration etc...) of the most commonly employed procedures are considered.

Amyotrophic Lateral Sclerosis↗
PubMed2003

[Symmetry and temporal variability of neurography].

UNLABELLED: The aims of the present study are to document side-to-side differences and temporal variability, between two trials (T1 and T2 at a time interval of 3 months) of nerve conduction measurements collected from 30 healthy subjects (mean age 22 +/- 2 years). METHODS: The protocol at T1 consisted of motor nerve conduction studies of median, ulnar, peroneal and tibial nerves bilaterally, with measurement of (a) motor response size (amplitude and area); (b) terminal latency; (c) minimal, mean and maximal F-wave latency; (d) motor conduction velocity; and (e) F-wave occurrence. T1 also involved sensory nerve conduction studies of median, ulnar, radial, lateral and medial cutaneous, sural and superficial peroneal nerves bilaterally, with measurement of sensory potential size (amplitude and area) and computation of sensory conduction velocity. The protocol at T2 consisted of identical measurements from the dominant side. RESULTS AND CONCLUSION: There was a negative relationship between the variability of parameters evaluating nervous conduction and the length of the nerve segment under study. Thus, the smallest side-to-side and temporal variabilities are measured for minimal F-wave latencies (on average 2-3%). The limits of symmetry and temporal variability are particularly useful for diagnosis of unilateral peripheral neuropathy or neurophysiological follow-up of patients with neuropathy, when the variability of the parameter under study is weak and when there is a high correlation between values recorded on the left and on the right or at T1 and T2. This was the case for motor response size of tibial and ulnar nerves, sensory potential size of radial nerve and minimal F-wave latencies from each studied motor nerve.

Adult↗
PubMed2003

Microscopic asperity contact and deformation of ultrahigh molecular weight polyethylene bearing surfaces.

The effect of the roughness and topography of ultrahigh molecular weight polyethylene (UHMWPE) bearing surfaces on the microscopic contact mechanics with a metallic counterface was investigated in the present study. Both simple sinusoidal roughness forms, with a wide range of amplitudes and wavelengths, and real surface topographies, measured before and after wear testing in a simple pin-on-plate machine, were considered in the theoretical analysis. The finite difference method was used to solve the microscopic contact between the rough UHMWPE bearing surface and a smooth hard counterface. The fast Fourier transform (FFT) was used to cope with the large number of mesh points required to represent the surface topography of the UHMWPE bearing surface. It was found that only isolated asperity contacts occurred under physiological loading, and the real contact area was only a small fraction of the nominal contact area. Consequently, the average contact pressure experienced at the articulating surfaces was significantly higher than the nominal contact pressure. Furthermore, it was shown that the majority of asperities on the worn UHMWPE pin were deformed in the elastic region, and consideration of the plastic deformation only resulted in a negligible increase in the predicted asperity contact area. Microscopic asperity contact and deformation mechanisms may play an important role in the understanding of the wear mechanisms of UHMWPE bearing surfaces.

Computer Simulation↗
PubMed2003

Elastohydrodynamic lubrication analysis of a functionally graded layered bearing surface, with particular reference to 'cushion form bearings' for artificial knee joints.

Elastohydrodynamic lubrication of a functionally graded layered (FGL) bearing surface, whose elastic modulus increases with depth from the bearing surface, was investigated in this study. The finite difference method was employed to solve the Reynolds equation, simultaneously with the elasticity equation of the bearing surface, under circular point contacts. The finite element method was adopted to solve the elasticity equation for the FGL bearing surface. The displacement coefficients thus obtained were used to calculate the elastic deformation of the bearing surface, required for the elastohydrodynamic lubrication analysis. Good agreement of the predicted film thickness and pressure distribution was obtained, between the present method and a previous study for a single layered bearing surface with a uniform elastic modulus. The general numerical methodology was then applied to an FGL bearing surface with both linear and exponential variations in elastic modulus, with particular reference to the 'cushion form bearing' for artificial knee joints. The predicted film thickness and pressure distribution were shown to be quite close to those obtained for a single layer under typical operating conditions representative of artificial knee joints, provided that the elastic modulus of the single layer was chosen to be the average elastic modulus of the graded layer.

Coated Materials, Biocompatible↗
PubMed2002

Changes in motor unit numbers in patients with ALS: a longitudinal study using the adapted multiple point stimulation method.

METHOD: The adapted multiple point stimulation (AMPS) method for calculating motor unit numbers (MUNE) was applied in 12 patients with amyotrophic lateral sclerosis (ALS) before riluzole therapy (T(0)) and again after 4, 8 and 12 months of treatment. RESULTS: Paired Student's t-test indicated a significant decrease of thenar MUNE and compound muscle action potential (CMAP) size at each 4-monthly interval, while average surface motor unit potential (SMUP) size did not change significantly over time. The rate of motor unit (MU) loss at month 4 was more than 20% in six patients (group 1) and less than 20% in six other patients (group 2). Comparison of groups 1 and 2 by Mann-Whitney U-testing indicated that percent changes in thenar MUNE and CMAP size compared to baseline were significantly different at months 4, 8 and 12, while no difference between the two groups was found for average SMUP size variations. In the group with a slow rate of MU loss, CMAP size remained stable, while in the group with a rapid rate of MU loss, there was a dramatic reduction in size of the CMAP. A positive correlation was found between percent change in thenar MUNE at T(4) and at T(12) (P < 0.001). CONCLUSION: AMPS is a useful technique to document MUNE, SMUP size and CMAP size changes over time in patients with ALS.

Action Potentials↗
PubMed2002

[Slow channel syndrome due to an autosomal translocation at 2q31-9p27].

A 27-year-old man complained of cervicoscapular and forearm weakness and amyotrophy. Electromyographic evaluation showed neuromuscular transmission dysfunction and a repetitive compound muscle action potential to a single stimulus. Prostigmine did not improve neuromuscular transmission. The genetic analysis of the patient's lymphocytes demonstrated a chromosomic 2q31-9p27 translocation. The combination of the clinical and electrophysiological data as well as the lack of auto-immunity signs against neuromuscular junction constituents led to the diagnosis to congenital postsynaptic myasthenic syndrome also called slow channel syndrome. This congenital myasthenic syndrome is for the first time associated with an autosomal translocation 2q31-9p27.

Action Potentials↗
PubMed2002

[Scapulo-peroneal weakness with tardive symptoms of facio-scapulo-humeral muscular dystrophy, connected to 4q35 chromosomal deletion].

We report the case of a 57-year-old woman, who presented with progressive weakness of ankle's dorsiflexors. Electromyography showed bilateral myogenic patterns in the anterior tibialis predominantly in the left side. Muscle biopsy of the right tibialis anterior showed non specific dystrophic changes. The familial evaluation revealed a son showing scapuloperoneal amyotrophy and facial involvement. Analysis of the propositus' DNA showed a mutation at locus 4q35, characteristic of facioscapulohumeral muscular dystrophy. This case illustrates the wide clinical spectrum of FSH dystrophy and the difficulty to diagnose unusual facial-sparing forms.

Chromosomes, Human, Pair 4↗
PubMed2001

Prognostic value of decremental responses to repetitive nerve stimulation in ALS patients.

Decrement of the thenar compound muscle action potentials (CMAP), after repetitive nerve stimulation (RNS) of the median nerve at 3 Hz, was evaluated in patients with ALS before riluzole therapy. CMAP size as well as motor unit number and size estimates were evaluated twice before and after 1 year of riluzole therapy. The correlation between decrement and CMAP size reduction per year was highly significant (r = 0.77), but no relationship could be demonstrated between decrement and other variables. The authors thus propose that decrement after RNS may be used as a predictor of further drop in CMAP size.

Action Potentials↗
PubMed2001

Legionnaires' disease in a patient with rheumatoid arthritis.

A 62-year-old male with rheumatoid arthritis (RA) who was taking nonsteroid anti-inflammatory drug for controlling synovitis developed a flare of his arthritis, hepatitis, and pneumonia due to infection with Legionella pneumophila serotype 1. Adult respiratory distress syndrome (ARDS) occurred following the development of pneumonia. After the introduction of erythromycin and ventilator support with positive end expiratory pressure (PEEP), his condition stabilized and he recovered gradually. We suggest that L. pneumophila should be considered early in the differential diagnosis of pneumonia in RA patients due to their immunocompromised status.

Arthritis, Rheumatoid↗
PubMed2001

[Entrapment neuropathies in sports medicine].

The more frequent entrapment neuropathies related to sport are described: thoracic outlet syndrome in aquatic athletes and pitchers, long thoracic neuropathy in tennis players, suprascapular neuropathy in volleyball and tennis players, ulnar nerve entrapment at the elbow in pitchers and at the wrist in cyclists, Morton's syndrome in runners and dancers.

Athletic Injuries↗
PubMed2001

[How I explore ... lumbar paraspinal muscle electromyography in the assessment of radiculopathy].

Lumbar paraspinal muscles examination is an interesting part of the electrodiagnostic evaluation of patients with suspected lumbosacral radiculopathy. However, many electromyographers hesitate to routinely include that technique in their study of lower limbs. The purpose of this paper is to specify the anatomy and electrophysiologic data of multifidus lumbar paraspinal muscle. Previous anatomic studies indicate that the medial lumbar multifidus and lumbar interspinalis muscles share unisegmental innervation by the dorsal ram of the spinal nerve. Electromyography of these muscles can improve the sensitivity of lumbosacral radiculopathy detection. Multi-MUP analysis of quantitative electromyographic parameters in lumbar paraspinal muscles, in a population of 75 healthy subjects without back pain, allowed to set up normal values for the L5 myotome.

Action Potentials↗
PubMed2000

Polymer additive analysis by pyrolysis-gas chromatography. IV. Antioxidants.

Antioxidants are important additives in polymers. Because of the low level of antioxidants normally used, they cannot be analyzed directly by common spectroscopic or thermal chemical techniques. However, antioxidants as well as other additives in polymers can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) after separating the polymers and additives. In this study, several antioxidants have been investigated to demonstrate that Py-GC is a viable tool to analyze them. The advantages of using Py-GC in the analysis of antioxidants have also been discussed.

Antioxidants↗
PubMed2000

Polymer additive analysis by pyrolysis-gas chromatography. III. Lubricants.

Lubricants are widely used in thermoplastic polymers to increase the overall rate of processing or to improve surface release properties. Because of the low level of lubricants normally used in a polymer, it may not be possible to analyze the additive directly by common spectroscopic or thermal chemical techniques. However, lubricants as well as other additives in the polymer can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) after extraction. In this work, several lubricants have been studied to demonstrate that Py-GC is a viable tool to investigate lubricants. The advantages of using Py-GC in the analysis of lubricant have also been discussed.

Chromatography, Gas↗
PubMed2000

Number-average molecular mass determination of polymeric material by pyrolysis-gas chromatography.

The number-average molecular mass of a polymeric material has been determined by pyrolysis-gas chromatography (Py-GC) via end-group analysis. The major advantage of this technique is that no sample preparation is required. The sample is not required to be in the dilute solution form, and the amount of sample needed is approximately 0.5 mg. Phenyl group-terminated polybutadiene systems have been studied as an example. The application of Py-GC to obtain the end-group concentration, the number-average molecular mass and the limitations of this method are discussed in detail. The success of this development elevates the role of Py-GC as an important technique for end-group analysis for the determination of number-average molecular mass.

Chromatography, Gas↗