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PubMed1998

Deficiency of lubricating surfactant lining the articular surfaces of replaced hips and knees.

While preceding papers have demonstrated that the active load-bearing agent in the boundary mode of joint lubrication is surface-active phospholipid (SAPL)--probably adsorbed as the outermost layer of articular cartilage--this study is designed to determine whether that layer is deficient in osteoarthritis (OA). This layer has been studied on 12 hips and 31 knees obtained from surgically replaced joints afflicted with OA. Measurement of the contact angle (theta) subtended by a droplet of saline clearly demonstrated a highly significant decrease in hydrophobicity, theta falling from 100 degrees for 13 bovine controls (78 degrees for five human controls) to 56 degrees for arthritic hips and 63 degrees and 68 degrees for the 'worn' and 'unworn' areas of arthritic knees, respectively. These changes were reflected in the quantities of SAPL (and proteolipid) recovered from the same articular surfaces by solvent rinsing, yields of SAPL being 36% lower in hips and 25% lower in 'worn' areas of knees, but not significantly different in 'unworn' areas. These results indicate that the outermost lubricating layer of SAPL deposited onto articular cartilage from SF is deficient in OA.

1,2-Dipalmitoylphosphatidylcholine↗

PubMedDate not supplied

Nonoxynol-9 in lubricated condoms. Results of a study in female prostitutes.

BACKGROUND AND OBJECTIVES: Debate continues on the efficacy and safety of intravaginal nonoxynol-9 for the prevention of horizontal transmission of human immunodeficiency and other sexually transmitted diseases. Little attention has been paid to the effects of nonoxynol-9 contained in the lubricant of many condoms. GOAL: To assess the tolerability of different levels of nonoxynol-9 in condom lubricants. STUDY DESIGN: Pilot, randomized, controlled trial in 70 female prostitutes. RESULTS: There was no association between dose of nonoxynol-9 and reported symptoms or signs of genital tract inflammation; an increased dose of nonoxynol-9 was associated with increased numbers of polymorphonuclear leukocytes on a vaginal wall smear. CONCLUSIONS: There is no recognized simple method of defining inflammation in the female genital tract. Future studies of the effects of low-dose nonoxynol-9 on the female genital tract require highly controlled exposures, plus colposcopy with or without vaginal biopsy to define inflammation.

Condoms↗

PubMed2005

Lubricating bacteria model for the growth of bacterial colonies exposed to ultraviolet radiation.

In this paper, we study the morphological transition of bacterial colonies exposed to ultraviolet radiation by modifying the bacteria model proposed by Delprato Our model considers four factors: the lubricant fluid generated by bacterial colonies, a chemotaxis initiated by the ultraviolet radiation, the intensity of the ultraviolet radiation, and the bacteria's two-stage destruction rate with given radiation intensities. Using this modified model, we simulate the ringlike pattern formation of the bacterial colony exposed to uniform ultraviolet radiation. The following is shown. (1) Without the UV radiation the colony forms a disklike pattern and reaches a constant front velocity. (2) After the radiation is switched on, the bacterial population migrates to the edge of the colony and forms a ringlike pattern. As the intensity of the UV radiation is increased the ring forms faster and the outer velocity of the colony decreases. (3) For higher radiation intensities the total population decreases, while for lower intensities the total population increases initially at a small rate and then decreases. (4) After the UV radiation is switched off, the bacterial population grows both outward as well as into the inner region, and the colony's outer front velocity recovers to a constant value. All these results agree well with the experimental observations [Phys. Rev. Lett. 87, 158102 (2001)]. Along with the chemotaxis, we find that lubricant fluid and the two-stage destruction rate are critical to the dynamics of the growth of the bacterial colony when exposed to UV radiation, and these were not previously considered.

Bacillus subtilis↗

PubMed2004

Soft lubrication.

We consider some basic principles of fluid-induced lubrication at soft interfaces. In particular, we quantify how a soft substrate changes the geometry of and the forces between surfaces sliding past each other. By considering the model problem of a symmetric nonconforming contact moving tangentially to a thin elastic layer, we determine the normal force in the small and large deflection limit, and show that there is an optimal combination of material and geometric properties which maximizes the normal force. Our results can be generalized to a variety of other geometries which show the same qualitative behavior. Thus, they are relevant in the elastohydrodynamic lubrication of soft elastic and poroelastic gels and shells, and in the context of biolubrication in cartilaginous joints.

Cartilage↗

PubMed1997

Laryngeal mask lubrication. A comparative study of saline versus 2% lignocaine gel with cuff pressure control.

We compared 2% lignocaine gel with saline as a lubricant for the laryngeal mask airway in 126 patients receiving positive pressure ventilation in whom cuff pressures were limited to 60 cmH2O and peak airway pressures to less than 17 cmH2O. The incidence of sore throat was similar for both groups and there were no emergence problems. There were significantly more intra- and postoperative complications in the lignocaine group (p < 0.05) but the frequency of sore throat was similar when the device was inserted at the first attempt. Positive pressure ventilation to normal end-tidal CO2 values was possible in all patients. Lignocaine gel is an unsuitable lubricant for the laryngeal mask airway. Cuff pressure limitation to 60 cmH2O does not necessarily impede ventilation and may be an important factor in reducing emergence and postoperative complications.

Anesthetics, Local↗

PubMed1994

Lignocaine gel used for lubrication of intranasal and endotracheal tubes in premature neonates.

In this study, we have measured the plasma concentration of lignocaine and its metabolite, monoethylglycinxylidin, in 19 premature neonates (gestational age < or = 33 weeks) when lignocaine gel was used for lubrication of an intranasal tube (during continuous positive airway pressure treatment) or an endotracheal tube (for intubation). We did not find any correlation between plasma concentration of lignocaine or monoethylglycinxylidin and weight of the infant (range 795-2530 g). None of the neonates had toxic levels of lignocaine. One neonate had an exceptionally high but not toxic plasma level of monoethylglycinxylidin. However, this neonate had been treated for severe seizures with an iv infusion of lignocaine up to 13 h before the study. In conclusion, we found it safe to use moderate amounts of lignocaine (i.e. 0.3 ml/kg of lignocaine gel 20 mg/ml) for lubricating both intranasal and endotracheal tubes.

Female↗

PubMed1977

The adhesion of film coatings to tablet surfaces--the effect of some direct compression excipients and lubricants.

The effect of some direct compression excipients and lubricants on the adhesion of hydroxypropyl methyl cellulose films has been examined using a specially designed tensile testing apparatus (Fisher & Rowe, 1976). The adhesion was found to be influenced by both the roughness, including microporosity, of the tablet surface and its polarity. Tablets prepared from microcrystalline cellulose showed very high adhesions despite having relatively smooth surfaces, owing to the surface being saturated with hydroxyl groups able to form hydrogen bonds with the corresponding groups on the polymer. The addition of magnesium or calcium stearate to the tablet was found to decrease the adhesion, but the addition of stearic acid caused a significant increase. The effect of lubricant concentration on the adhesion could be expressed by an equation similar to that proposed by Hofrichter & McLaren (1948) for the adhesion of vinyl chloride/vinyl acetate copolymers to regenerated cellulose.

Adhesiveness↗

PubMed1989

Boundary conditions at the cartilage-synovial fluid interface for joint lubrication and theoretical verifications.

The objective of this study is to establish and verify the set of boundary conditions at the interface between a biphasic mixture (articular cartilage) and a Newtonian or non-Newtonian fluid (synovial fluid) such that a set of well-posed mathematical problems may be formulated to investigate joint lubrication problems. A "pseudo-no-slip" kinematic boundary condition is proposed based upon the principle that the conditions at the interface between mixtures or mixtures and fluids must reduce to those boundary conditions in single phase continuum mechanics. From this proposed kinematic boundary condition, and balances of mass, momentum and energy, the boundary conditions at the interface between a biphasic mixture and a Newtonian or non-Newtonian fluid are mathematically derived. Based upon these general results, the appropriate boundary conditions needed in modeling the cartilage-synovial fluid-cartilage lubrication problem are deduced. For two simple cases where a Newtonian viscous fluid is forced to flow (with imposed Couette or Poiseuille flow conditions) over a porous-permeable biphasic material of relatively low permeability, the well known empirical Taylor slip condition may be derived using matched asymptotic analysis of the boundary layer at the interface.

Cartilage, Articular↗

PubMed1982

Modes of lubrication in human hip joints.

Cadaveric hip joints were tested in a hip function simulator which subjected the femoral head to a cycle of loading and oscillation similar to that experienced during walking and measured the frictional torque transmitted to the acetabulum. Silicone fluids with viscosities from 10-2 Pa s (pascal second) to 30 Pa s were used as lubricants and the transition from mixed to full fluid film lubrication was observed around 5 x 10(-2) Pa s. Sodium carboxymethylcellulose solutions were also tested at the lower viscosities. Hyaluronidase digestion of samples of synovial fluid caused a significant increase in friction over the control samples. Trypsin digestion had no significant effect. No correlation between compliance of the cartilage and the frictional values was observed.

Elasticity↗

PubMed1982

Boundary lubrication imparted by pleural surfactants and their identification.

Phospholipids have been identified in pleural washings from live dogs and were found to include phosphatidylethanolamines, sphingomyelin, and, predominantly, phosphatidylcholines. The extracts were highly surface active when studied on the Langmuir trough using a Wilhelmy balance and produced surface tension/area loops similar to those for synthetic phosphatidylcholines and phosphatidylethanolamines but differing from the pure dipalmitoyl derivative (DPL). The extracts, the synthetic surfactants and their mixtures, were all found to be good lubricants when tested by a standard method for evaluating textile "sizes." The results are consistent with the classical theory of "boundary" lubrication for which surfactant molecules would have an almost ideal molecular structure for adsorption, film cohesion, and mutual interaction of the hydrophobic ends. This concept is suggested as a mechanism that can explain some of the anomalies in the hydrodynamic theory of sliding of the pleurae and may possibly apply to other surfaces.

Animals↗

PubMed1998

Water-soluble cooling lubricants induce airway hyperresponsiveness in rabbits.

Airway hyperresponsiveness (AHR) to water-soluble cooling lubricants (CL) induced by aerosol administered by tracheal tube was studied in a rabbit model of occupational lung disease. Two commercial CL were examined: the first was of the boric acid amine ester type without biozide (CL-BAE), the second was of the sulfonate type with biozide (CL-SB). 50, 5.0 or 0.5 mg/m3 CL was administered over a period of twice 2 h to six different groups of rabbits. Airway responsiveness (AR) to aerosols of 0.2% and 2.0% acetylcholine solution (ACH) was measured before and after each exposure to CL. A control group A of nine animals not exposed to CL showed no significant respiratory responses following inhalation of 0.2% ACH for 1 min. Conversely, inhalation of 2.0% ACH almost doubled the dynamic elastance (Edyn) in the ACH challenge test in this animal group. Airway resistance (RI), Edyn, slope of inspiratory pressure generation (delta Pes/tI), arterial pressure (Pa) and arterial blood gas tensions (PaO2, PaCO2) were not significantly altered during and after exposures to CL. However, after CL-BAE inhalation of 50 and 5 mg/m3 over 4 h, the amplitude of the ACH-induced airway obstruction indicated by the changes in Edyn rose significantly to almost five times the control response before exposure (group C, D, p < 0.005). Similar changes in RI and delta Pes/tI were obtained. After inhalation of 0.5 mg/m3 CL-BAE (group D), no significant changes in AR were observed. Similar to CL-BAE inhalation of 50 mg/m3, CL-SB caused enlarged AR in the ACH challenge test (group E), whereas no significant changes were found after exposure to 5.0 and 0.5 mg/m3 in groups F and G. In summary, CL aerosols with and without biozide in the range of 50 and 5 mg/m3 applied via tracheal tubes increased AR to ACH within 4 h of exposure in a time- and concentration-dependent manner. It has to be assumed that this augmented AR indicates an increased risk of developing lubricant-induced obstructive lung diseases.

Acetylcholine↗

PubMed2005

Diatom bionanotribology--biological surfaces in relative motion: their design, friction, adhesion, lubrication and wear.

Tribology is the branch of engineering that deals with the interaction of surfaces in relative motion (as in bearings or gears): their design, friction, adhesion, lubrication and wear. Continuous miniaturization of technological devices like hard disc drives and biosensors increases the necessity for the fundamental understanding of tribological phenomena at the micro- and nanoscale. Biological systems show optimized performance also at this scale. Examples for biological friction systems at different length scales include bacterial flagella, joints, articular cartilage and muscle connective tissues. Scanning probe microscopy opened the nanocosmos to engineers: not only is microscopy now possible on the atomic scale, but even manipulation of single atoms and molecules can be performed with unprecedented precision. As opposed to this top-down approach, biological systems excel in bottom-up nanotechnology. Our model system for bionanotribological investigations are diatoms, for they are small, highly reproductive, and since they are transparent, they are accessible with different kinds of optical microscopy methods. Furthermore, certain diatoms have proved to be rewarding samples for mechanical and topological in vivo investigations on the nanoscale. There are several diatom species that actively move (e.g. Bacillaria paxillifer forms colonies in which the single cells slide against each other) or which can, as cell colonies, be elongated by as much as a major fraction of their original length (e.g. Ellerbeckia arenaria colonies can be reversibly elongated by one third of their original length). Therefore, we assume that some sort of lubrication of interactive surfaces is present in these species. Current studies in diatom bionanotribology comprise techniques like atomic force microscopy, histochemical analysis, infrared spectrometry, molecular spectroscopy and confocal infrared microscopy.

Cell Adhesion↗

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↗

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↗

PubMed1997

Wear of ultra-high molecular weight polyethylene acetabular cups in a physiological hip joint simulator in the anatomical position using bovine serum as a lubricant.

The Leeds physiological anatomical (PA) hip joint simulator was developed to apply three axes of loading and a complex three-dimensional motion so that the forces and motions can reproduce exactly the walking cycles defined by Paul. This paper presents the results of a study using the Leeds PA hip joint simulator to determine the wear of 32 mm ultra-high molecular weight polyethylene (UHMWPE) acetabular cups against stainless steel and zirconia ceramic heads, using bovine serum as lubricant. These results have been compared with the results of a previous study that used water as the lubricant, which led to UHMWPE transfer film being formed on the stainless steel head. Comparisons are also made with clinical results and results from other simulators. The study indicates that it is preferable to use bovine serum in simulator studies. In addition, the results indicate that if the surface roughness of the metallic and femoral heads are similar, and they remain undamaged during the tests, the wear rates of the UHMWPE cups are likely to be similar.

Acetabulum↗

PubMed2006

The role of the surface amorphous layer of articular cartilage in joint lubrication.

Articular cartilage is a complex soft tissue that performs multiple functions in the joint. In particular, the amorphous layer that covers the surface of articular cartilage is thought to play some role in lubrication. This study aimed to characterize the surface amorphous layer (SAL) using a variety of techniques, including environmental scanning electron microscopy, transmission electron microscopy, white light interferometry, and biochemical analysis of its composition. Friction tests were conducted to investigate the role of the SAL in lubrication. A protocol to remove successfully the SAL without damaging the underlying cartilage was developed and the material removed from healthy cartilage was found to contain approximately equal quantities of glycosaminoglycan (GAG), protein, and lipid. Cartilage-on-cartilage friction tests were conducted on fresh, healthy cartilage with and without the SAL, under both dynamic and static operating conditions. Removal of the SAL was not found to change the friction coefficient. However, subsequent staining of specimens indicated that the SAL had replenished during the test following loading. The replenished SAL was characterized and found to contain lipids and sulphated GAGs with undetectable protein. This study revealed experimental evidence of surface layer replenishment in articular cartilage. It was postulated that the surface layer regeneration mechanism was purely mechanical and associated with movement of GAGs and lipids through the cartilage matrix during deformation, since the experimental set-up did not contain any means of biochemical activation.

Animals↗

PubMed1993

Recommendations with respect to the improvement of lubricating qualities of synovial fluid in artificial joints.

This paper gives a short description of the lubricating properties of yellow and red bone marrow taken from a femur of a cadaver. The experiments have been conducted on a 'ball-on-plate' model. The balls were made from steel 100 CR6 (German) and the plates were made from the same steel and ultra-high molecular weight polyethylene (UHMWPE, German 'Herulen'). The friction coefficients under loads of 50 and 300 N were determined with different combinations of friction components. It has been found that the lubricating properties of yellow and red marrow have advantages over synovial fluid. In the light of these results the author develops a new approach to the design of a new hip endoprosthesis.

Bone Marrow↗

PubMedDate not supplied

InstantCath from Hollister: pre-lubricated self-catheterization.

Over the centuries a variety of substances have been used to make a hollow tube to pass through the urethra to empty a poorly functioning bladder. The ancient Greeks used dried water reeds from the riverbank. The Romans and the Egyptians experimented with gold and silver. Following the industrial revolution stainless steel was used and catheters are still manufactured today using stainless steel. PVC and plastic catheters became popular in the 1970s and various hydrophilic coatings have been added to provide self-lubrication of the catheter when it comes into contact with water. The most recent development in the clean, intermittent self-catheterization (CISC) range is the Hollister InstantCath which is a self-lubricating catheter that does not require any water. It has shown itself to be well received by patients and is a welcome addition to the choice available to healthcare professionals and their patients when instigating CISC as therapy.

Equipment Design↗