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Orthopaedic Tribology For Postgraduate Orthopaedic Exams
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Orthopaedic Tribology For Postgraduate Orthopaedic Exams
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Language: EN.
Segment:0 .
Good evening, everyone, thank you very much for attending our joint webinar session between author of peak Academy and orthopedic Research UK. Today, we're really grateful to have Professor Mathias doing his presentation on tribe biology, a very important topic that will come up quite a lot within the basic science parts of the vyver and also very key component as part of our day to day work in arthroplasty.
And I would advise you to listen very carefully and take note of a lot of the important things that will be discussed today. And this will be take around half an hour or so, there'll be a poll of questions in between to make sure people are paying attention. But please also if you've got any questions, can you put them in the chat box? And for us, we'll take note of it.
And after the presentation, we will go through the questions people have got to ask. We also do afterwards, we'll do a hot seat practice, Viva with three candidates where we'll try and discuss some of the tribal and basic science components that have come up today. And we'll do this in the style, as we've done before, where we'll have five minutes for questions and feedback from people doing the questioning.
And hopefully this will take we'll be able to finish at 830. So without further ado, I will hand you over to Professor Suarez. Thank you very much. So good evening, everyone. It is my pleasure to meet you once more in the first webinar for the year 2022. We will take off where we left last December.
Having covered the principles of biomechanics, we are now aiming to venture into the topic of tribalism. My name is Emma Willis and I am one of the orthopedic doctors at traject teaching hospital in Cairo. When the internet community was asked. What trade policy was all sorts of bizarre definitions came up, while trade policy has definitely nothing to do with Three Legged races.
It is the study of interactions between two solid surfaces in relative motion. Biotechnology, in turn, is trade policy borrowed by biologists from engineers. Different combinations of friction, lubrication and where are required, depending on the desired interaction of moving objects. Therefore, by the end of this presentation, you shall be able to describe the principles of friction, lubrication and where and apply them to our natural and artificial articulations.
If you have attended the last webinar on biomechanics, the following example should be familiar. Take this block, which has a mass of m under the effect of gravity. It pushes on the surface with a force equal to its mass multiplied by the acceleration due to gravity. According to Newton's third law, the surface is in turn push against the block by an equal and opposite force called here force normal, being perpendicular to the surface.
If we start to tilt the surface, the force due to gravity will remain in vertically Downward direction. However, the force normal will have to remain perpendicular to the surface. To estimate this force, we resolve the force due to gravity into its components, although the force normal will consequently become smaller. However, the parallel component of the force due to gravity will attempt to move the block down the slope.
Being opposed by an equal and opposite force, the block remains in equilibrium. This opposing force is the force due to friction. The more you tilt the surface, the bigger the parallel component of the force due to gravity becomes, and hence the force due to friction would have to increase in order to keep the block in equilibrium. So as the parallel component continues to increase, the force of friction will also increase from 0 to a maximum in order to keep the block from moving.
There is going to be a point where the force of friction will not be able to resist the moving force, at which point the block will start to slide. It is obvious that the block will start to slide at a smaller angle if the surface were rough as wood, for example, compared for four compared with a smooth surface such as glass. The force due to friction will obviously depend on the nature of the two interacting surfaces.
The heavier the object, the more difficult it would be to move. Friction is therefore a force that resists relative motion between two interacting surfaces, either due to adhesions caused by surface roughness or viscosity of the shearing lubricant film between them. There is another type of internal friction, which occurs inside a material or structure and is not considered in this lecture.
We have seen from the previous example that the force due to friction is proportional to the normal loads on the surface. Friction does not depend on the contact area or sliding speed of the two surfaces. Therefore, the contact area between the surfaces can be increased to reduce the pressure without increasing the friction. The coefficient of friction mu indicates how much force per unit load is required to initiate sliding motion between the two surfaces.
It has no units and depends on the roughness of the interacting surfaces. It takes more force to initiate than to continue sliding. Hence, the static coefficient of friction US is always larger than the dynamic coefficient of friction. New D. The typical examples in the table indicate the coefficient of friction between your car tire and the ground train wheels, and the railway put metal on pulley articulation and metal on Teflon, which is PTFE given its low coefficient of friction.
It is no wonder that Sir John Charnley chose Teflon to make his early acellular cups. The disadvantage of Teflon will be explained later. Since no surface is perfectly smooth, areas of surface roughness ultimately called as parities result in localized contact between any interacting surfaces, the true area of contact is therefore proportional to the normal load and inversely proportional to the hardness.
Under very high stresses, the summits of the parities bond together the bond strength being proportional to the true contact area. Based on what we have learned so far, consider this question. Assuming a similar combination of. Interacting of blocks and surfaces which block experiences more friction, please vote. Absolutely brilliant. The block in figure C is obviously larger than the other two blocks, since all blocks have a similar material.
Its mass is bigger. Hence the normal load, which is proportional to friction will be larger. Coefficient of friction is the same for any two combinations of materials. The surface area does not affect friction, which depends on the true contact area. And hence the normal load. In addition to causing where of the moving surfaces, friction increases the load at the bone implant interface, which might result in loosening friction force itself is proportional to normal load on the implant and does not change with different femoral head sizes.
On the other hand, frictional torque on the acetabular cup, which is proportional to the coefficient of friction of the articulating surfaces as well as the head diameter increases with the larger femoral head size. Figures in the table show why surgeons only elected to make his femoral heads as small as 22 millimeters at the bottom row. The advantage of initially selecting Teflon with a very low coefficient of friction in combination with a small femoral head is clear.
We have so far considered the principles of dry friction, the addition of a fluid between the two surfaces with its low shear strength results in motion within the film, hence reducing friction and where we have all experienced how the car tires on the first row skid on a wet ground or a wet road during rain, although the coefficient of friction in artificial joints is markedly reduced in the lubricated state.
It is still nowhere near that of the natural joints. This brings us to the topic of lubrication. A lubricant is a substance introduced between the sliding surfaces in order to reduce friction and where it could either be a solid, liquid, or gas. Interacting surfaces need to slide relative to each other at a reasonable speed in order to maintain an adequate fluid film.
This is much like water skiing. The ski skis are initially stationary. The skier tends to sink in the water under her weight. However, once the boat starts to pick up speed, she is kept floating by the velocity of the boat and the viscosity of the water. The slope of the ski is represented by the clearance between the acetabular cup and the femoral head at both ends of the spectrum, we have the two surfaces either in contact with each other, being covered only by a very thin film of fluid or completely separated from each other by an uninterrupted fluid film.
Increasing load will shift the conditions towards boundary lubrication while increasing the velocity of motion. Viscosity of the fluid or effective radius would foster hydrodynamic lubrication when the fluid filled between the interacting surfaces is about the same thickness as their surface roughness as operatives on the opposing surfaces get in contact, resulting in a high coefficient of friction.
On the other hand, fluid film completely separates the interacting surfaces in hydrodynamic lubrication, such that any motion occurs between the layers of the fluid filled. The slope of this key in the water skiing example represents the radial clearance of the implants. This is the degree of mismatch between the radius of the femoral head and the acetabular cup. Clearance determines the effective radius, which in engineering terms is the radius of the ball when the ball in the socket is converted to a ball on plain.
The fluid film thickness depends on multiple factors, as in the example of the water key it increases with the increase in the viscosity of the lubricant, the relative velocity of the surfaces and the effective radius. The fluid film thickness decreases with the stress across the interface. Contrary to friction, which is independent of the contact surface area, lubrication of the larger head is much better than that of a smaller femoral head.
The above factors describe what is called Summerfield number or the film factors. Because the relationship between coefficient of friction and bearing parameter is complex, it is easier to present it with a curve rather than with an equation when articulating components are stationary. The coefficient of friction is relatively high and the components are only separated by thin fluid, often what is called boundary lubrication as the components start to move relative to each other.
The coefficient of friction drops as the one component starts to float on top of the progressively thicker, fluid filled. In the hydrodynamic region of the curve, although a fluid film completely separates both components, the coefficient of friction starts to rise slightly because of drag between the layers of fluid. Because of the surface roughness of polyethylene, hard on soft articulations like metal claw palsy can only have boundary lubrication hard on hard articulations, on the other hand, experience mixed and fluid filled hydrodynamic lubrication.
In order to move from 30 degrees of flexion to 15 degrees of extension, a small femoral head would have to trouble. Excuse me. A short distance to cover, it's 45 degrees angle. A larger femoral head, in contrast, would have a larger sliding distance to cover in the same range of motion. In the same time, although the larger head has an advantage in terms of better stability and range of motion because of the larger sliding distance.
It also has an increased wear rate. On the other hand, because the larger, effective radius and high velocity, the larger femoral heads are more suitable for heart on heart articulations wear mixed and fluid film lubrication occurs. This advantage is not experienced by the heart on soft articulations, which can only be lubricated by boundary lubrication. Another advantage of the larger heads is the reduction of stress due to a larger area of contact, thus enhancing fluid film thickness.
The initial combination surgeons used a 22 head with metal on polyethylene. Articulation resulted in high wear and less stability, increasing the head size to 28 increased the stability at the expense of wear. Changing the articulation into highly cross-linked polyethylene has definitely reduced wear rate. Increasing the head size to 36 proved to be a reasonable compromise.
On the other hand, hard on hard articulations have shown reduced rate of wear. Using a larger head in this type of articulation definitely increases the stability without affecting wear very much. With our knowledge about lubrication. So far, I would like you to think as to which mechanism was related to failure and device recall in the case of the ESR hip resurfacing.
Please vote, explain the question a little bit at the time. The correct answer is B. The ESR acetabular cup had an inside groove against which a surgeon pressed a tool to implant the component. The groove limited the surface area inside the cup. As a result, the ball was more likely to strike the Kupp's edge, causing wear and generating metallic debris. This was particularly prone to occur when the cup had a more open inclination.
Fig. E shows the adequate clearance with polar bearing of the articulation. Figure C shows equatorial bearing and figure D shows fully congruent articulation in both cases there. There was no clearance for the no clearance for the fluid filled movement inside the hip. So what you want is an adequate clearance like in figure A That brings us to the discussion on the topic of where is the progressive loss of material?
As a result of relative motion between articulating bodies, it results in a change in the shape and size of the objects and produces where debris, as in the program weakest link, it is the softest and weakest material that usually suffers the most. There are full general subject areas in relation to where, where, modes, where mechanisms, where damage and where debris.
In both one, where occurs between two primary articulating services, remember primary versus primary is 1 times 1 n is equal to where no one in mode to wear a bearing and a non bearing surface are rubbing against each other. Both three occurs as a result of third body particles, and most fall occurs between two non articulating surfaces.
Remember, secondary versus secondary, which is 2 times 2 equals 4. Examples include mode one normal where that occurs between the femoral head and the acetabular liner, both two is represented by micro separation and stripe, where between the femoral head and the non articular edge of the acetabular liner. Both 3 is the third body adhesive abrasive wear and what four here represented by impingement between the femoral neck and the edge of the cup, or the backside where between the liner and the shell, the previous wear modes can occur because of any combination of the following mechanisms adhesive, where results from deformation of spot welds between the two surfaces with subsequent breakage of the transfer film resulting in third body particles.
Abrasive weather is similarly it's like using sandpaper where a spirit is on the harder surface causes plowing of the softer one. Fatigue where results in subsurface cracks, which eventually communicate, causing elimination. Thus, the primary where mechanisms can either result from low rate abrasive wear, which does not involve transfer of material from one to the other.
Adhesive moderate rate wear, which results in transfer of material from the softer surface to the harder one or higher rate. Third, body wear adding corrosive wear to any of the three mechanical wear mechanisms result in market acceleration of the process. The above mechanisms result in change in texture of the shape or the shape of the implant.
The resultant damage has been expressed by a long list of descriptive terms where generates billions of particles which initiate biological reaction. Local effects depend on the size and number of particles, which either with either macrophage activation leading to granuloma formation or lymphocytic reaction resulting in pseudo tumors. The result?
The smaller metal ions could escape into the systemic circulation, resulting in carcinogenesis or teratogenic city. Here is another poll question in which articulation do where particles result in granuloma formation as a body response leading to osteoporosis. Please vote. The correct answer is C where the polyethylene particles are known to cause macrophage activation and granuloma formation with osteogenesis, metal or metal articulation in figure A usually result in lesions such as pseudotumor or valw or a RMG.
While ceramic on ceramic articulations are biologically inert, linear wear can be measured on X-ray or other special techniques by head penetration in millimeters or millimeters per year. Volumetric wear is measured or calculated in millimeters, cube or millimeters per year. Using simplified equation, assuming that the head produces a cylindrical bowl, many of you will be familiar with this illustration, which shows how much where volume is produced by different combinations of varying surfaces.
It is, however, the size and number of particles which determines the biological effect of the wear debris. Although the volumetric wear is much less a metal or metal articulations, particle size is much smaller slap micron, resulting in billions of particles being produced with each step. Debris production is initially accelerated in the initial wearing in phase, however, it later reduces and reaches a steady state.
Where volume is directly proportionate to the normal load, but and not the stresses and the sliding distance that the articulating surfaces experience, it is inversely proportionate to the hardness of the softer component. Using this information, one can calculate a unitless where coefficient, as well as a more specific wear factor. This is where the disadvantage of Teflon becomes clear.
It's
Segment:0 .
Good evening, everyone, thank you very much for attending our joint webinar session between author of peak Academy and orthopedic Research UK. Today, we're really grateful to have Professor Mathias doing his presentation on tribe biology, a very important topic that will come up quite a lot within the basic science parts of the vyver and also very key component as part of our day to day work in arthroplasty.
And I would advise you to listen very carefully and take note of a lot of the important things that will be discussed today. And this will be take around half an hour or so, there'll be a poll of questions in between to make sure people are paying attention. But please also if you've got any questions, can you put them in the chat box? And for us, we'll take note of it.
And after the presentation, we will go through the questions people have got to ask. We also do afterwards, we'll do a hot seat practice, Viva with three candidates where we'll try and discuss some of the tribal and basic science components that have come up today. And we'll do this in the style, as we've done before, where we'll have five minutes for questions and feedback from people doing the questioning.
And hopefully this will take we'll be able to finish at 830. So without further ado, I will hand you over to Professor Suarez. Thank you very much. So good evening, everyone. It is my pleasure to meet you once more in the first webinar for the year 2022. We will take off where we left last December.
Having covered the principles of biomechanics, we are now aiming to venture into the topic of tribalism. My name is Emma Willis and I am one of the orthopedic doctors at traject teaching hospital in Cairo. When the internet community was asked. What trade policy was all sorts of bizarre definitions came up, while trade policy has definitely nothing to do with Three Legged races.
It is the study of interactions between two solid surfaces in relative motion. Biotechnology, in turn, is trade policy borrowed by biologists from engineers. Different combinations of friction, lubrication and where are required, depending on the desired interaction of moving objects. Therefore, by the end of this presentation, you shall be able to describe the principles of friction, lubrication and where and apply them to our natural and artificial articulations.
If you have attended the last webinar on biomechanics, the following example should be familiar. Take this block, which has a mass of m under the effect of gravity. It pushes on the surface with a force equal to its mass multiplied by the acceleration due to gravity. According to Newton's third law, the surface is in turn push against the block by an equal and opposite force called here force normal, being perpendicular to the surface.
If we start to tilt the surface, the force due to gravity will remain in vertically Downward direction. However, the force normal will have to remain perpendicular to the surface. To estimate this force, we resolve the force due to gravity into its components, although the force normal will consequently become smaller. However, the parallel component of the force due to gravity will attempt to move the block down the slope.
Being opposed by an equal and opposite force, the block remains in equilibrium. This opposing force is the force due to friction. The more you tilt the surface, the bigger the parallel component of the force due to gravity becomes, and hence the force due to friction would have to increase in order to keep the block in equilibrium. So as the parallel component continues to increase, the force of friction will also increase from 0 to a maximum in order to keep the block from moving.
There is going to be a point where the force of friction will not be able to resist the moving force, at which point the block will start to slide. It is obvious that the block will start to slide at a smaller angle if the surface were rough as wood, for example, compared for four compared with a smooth surface such as glass. The force due to friction will obviously depend on the nature of the two interacting surfaces.
The heavier the object, the more difficult it would be to move. Friction is therefore a force that resists relative motion between two interacting surfaces, either due to adhesions caused by surface roughness or viscosity of the shearing lubricant film between them. There is another type of internal friction, which occurs inside a material or structure and is not considered in this lecture.
We have seen from the previous example that the force due to friction is proportional to the normal loads on the surface. Friction does not depend on the contact area or sliding speed of the two surfaces. Therefore, the contact area between the surfaces can be increased to reduce the pressure without increasing the friction. The coefficient of friction mu indicates how much force per unit load is required to initiate sliding motion between the two surfaces.
It has no units and depends on the roughness of the interacting surfaces. It takes more force to initiate than to continue sliding. Hence, the static coefficient of friction US is always larger than the dynamic coefficient of friction. New D. The typical examples in the table indicate the coefficient of friction between your car tire and the ground train wheels, and the railway put metal on pulley articulation and metal on Teflon, which is PTFE given its low coefficient of friction.
It is no wonder that Sir John Charnley chose Teflon to make his early acellular cups. The disadvantage of Teflon will be explained later. Since no surface is perfectly smooth, areas of surface roughness ultimately called as parities result in localized contact between any interacting surfaces, the true area of contact is therefore proportional to the normal load and inversely proportional to the hardness.
Under very high stresses, the summits of the parities bond together the bond strength being proportional to the true contact area. Based on what we have learned so far, consider this question. Assuming a similar combination of. Interacting of blocks and surfaces which block experiences more friction, please vote. Absolutely brilliant. The block in figure C is obviously larger than the other two blocks, since all blocks have a similar material.
Its mass is bigger. Hence the normal load, which is proportional to friction will be larger. Coefficient of friction is the same for any two combinations of materials. The surface area does not affect friction, which depends on the true contact area. And hence the normal load. In addition to causing where of the moving surfaces, friction increases the load at the bone implant interface, which might result in loosening friction force itself is proportional to normal load on the implant and does not change with different femoral head sizes.
On the other hand, frictional torque on the acetabular cup, which is proportional to the coefficient of friction of the articulating surfaces as well as the head diameter increases with the larger femoral head size. Figures in the table show why surgeons only elected to make his femoral heads as small as 22 millimeters at the bottom row. The advantage of initially selecting Teflon with a very low coefficient of friction in combination with a small femoral head is clear.
We have so far considered the principles of dry friction, the addition of a fluid between the two surfaces with its low shear strength results in motion within the film, hence reducing friction and where we have all experienced how the car tires on the first row skid on a wet ground or a wet road during rain, although the coefficient of friction in artificial joints is markedly reduced in the lubricated state.
It is still nowhere near that of the natural joints. This brings us to the topic of lubrication. A lubricant is a substance introduced between the sliding surfaces in order to reduce friction and where it could either be a solid, liquid, or gas. Interacting surfaces need to slide relative to each other at a reasonable speed in order to maintain an adequate fluid film.
This is much like water skiing. The ski skis are initially stationary. The skier tends to sink in the water under her weight. However, once the boat starts to pick up speed, she is kept floating by the velocity of the boat and the viscosity of the water. The slope of the ski is represented by the clearance between the acetabular cup and the femoral head at both ends of the spectrum, we have the two surfaces either in contact with each other, being covered only by a very thin film of fluid or completely separated from each other by an uninterrupted fluid film.
Increasing load will shift the conditions towards boundary lubrication while increasing the velocity of motion. Viscosity of the fluid or effective radius would foster hydrodynamic lubrication when the fluid filled between the interacting surfaces is about the same thickness as their surface roughness as operatives on the opposing surfaces get in contact, resulting in a high coefficient of friction.
On the other hand, fluid film completely separates the interacting surfaces in hydrodynamic lubrication, such that any motion occurs between the layers of the fluid filled. The slope of this key in the water skiing example represents the radial clearance of the implants. This is the degree of mismatch between the radius of the femoral head and the acetabular cup. Clearance determines the effective radius, which in engineering terms is the radius of the ball when the ball in the socket is converted to a ball on plain.
The fluid film thickness depends on multiple factors, as in the example of the water key it increases with the increase in the viscosity of the lubricant, the relative velocity of the surfaces and the effective radius. The fluid film thickness decreases with the stress across the interface. Contrary to friction, which is independent of the contact surface area, lubrication of the larger head is much better than that of a smaller femoral head.
The above factors describe what is called Summerfield number or the film factors. Because the relationship between coefficient of friction and bearing parameter is complex, it is easier to present it with a curve rather than with an equation when articulating components are stationary. The coefficient of friction is relatively high and the components are only separated by thin fluid, often what is called boundary lubrication as the components start to move relative to each other.
The coefficient of friction drops as the one component starts to float on top of the progressively thicker, fluid filled. In the hydrodynamic region of the curve, although a fluid film completely separates both components, the coefficient of friction starts to rise slightly because of drag between the layers of fluid. Because of the surface roughness of polyethylene, hard on soft articulations like metal claw palsy can only have boundary lubrication hard on hard articulations, on the other hand, experience mixed and fluid filled hydrodynamic lubrication.
In order to move from 30 degrees of flexion to 15 degrees of extension, a small femoral head would have to trouble. Excuse me. A short distance to cover, it's 45 degrees angle. A larger femoral head, in contrast, would have a larger sliding distance to cover in the same range of motion. In the same time, although the larger head has an advantage in terms of better stability and range of motion because of the larger sliding distance.
It also has an increased wear rate. On the other hand, because the larger, effective radius and high velocity, the larger femoral heads are more suitable for heart on heart articulations wear mixed and fluid film lubrication occurs. This advantage is not experienced by the heart on soft articulations, which can only be lubricated by boundary lubrication. Another advantage of the larger heads is the reduction of stress due to a larger area of contact, thus enhancing fluid film thickness.
The initial combination surgeons used a 22 head with metal on polyethylene. Articulation resulted in high wear and less stability, increasing the head size to 28 increased the stability at the expense of wear. Changing the articulation into highly cross-linked polyethylene has definitely reduced wear rate. Increasing the head size to 36 proved to be a reasonable compromise.
On the other hand, hard on hard articulations have shown reduced rate of wear. Using a larger head in this type of articulation definitely increases the stability without affecting wear very much. With our knowledge about lubrication. So far, I would like you to think as to which mechanism was related to failure and device recall in the case of the ESR hip resurfacing.
Please vote, explain the question a little bit at the time. The correct answer is B. The ESR acetabular cup had an inside groove against which a surgeon pressed a tool to implant the component. The groove limited the surface area inside the cup. As a result, the ball was more likely to strike the Kupp's edge, causing wear and generating metallic debris. This was particularly prone to occur when the cup had a more open inclination.
Fig. E shows the adequate clearance with polar bearing of the articulation. Figure C shows equatorial bearing and figure D shows fully congruent articulation in both cases there. There was no clearance for the no clearance for the fluid filled movement inside the hip. So what you want is an adequate clearance like in figure A That brings us to the discussion on the topic of where is the progressive loss of material?
As a result of relative motion between articulating bodies, it results in a change in the shape and size of the objects and produces where debris, as in the program weakest link, it is the softest and weakest material that usually suffers the most. There are full general subject areas in relation to where, where, modes, where mechanisms, where damage and where debris.
In both one, where occurs between two primary articulating services, remember primary versus primary is 1 times 1 n is equal to where no one in mode to wear a bearing and a non bearing surface are rubbing against each other. Both three occurs as a result of third body particles, and most fall occurs between two non articulating surfaces.
Remember, secondary versus secondary, which is 2 times 2 equals 4. Examples include mode one normal where that occurs between the femoral head and the acetabular liner, both two is represented by micro separation and stripe, where between the femoral head and the non articular edge of the acetabular liner. Both 3 is the third body adhesive abrasive wear and what four here represented by impingement between the femoral neck and the edge of the cup, or the backside where between the liner and the shell, the previous wear modes can occur because of any combination of the following mechanisms adhesive, where results from deformation of spot welds between the two surfaces with subsequent breakage of the transfer film resulting in third body particles.
Abrasive weather is similarly it's like using sandpaper where a spirit is on the harder surface causes plowing of the softer one. Fatigue where results in subsurface cracks, which eventually communicate, causing elimination. Thus, the primary where mechanisms can either result from low rate abrasive wear, which does not involve transfer of material from one to the other.
Adhesive moderate rate wear, which results in transfer of material from the softer surface to the harder one or higher rate. Third, body wear adding corrosive wear to any of the three mechanical wear mechanisms result in market acceleration of the process. The above mechanisms result in change in texture of the shape or the shape of the implant.
The resultant damage has been expressed by a long list of descriptive terms where generates billions of particles which initiate biological reaction. Local effects depend on the size and number of particles, which either with either macrophage activation leading to granuloma formation or lymphocytic reaction resulting in pseudo tumors. The result?
The smaller metal ions could escape into the systemic circulation, resulting in carcinogenesis or teratogenic city. Here is another poll question in which articulation do where particles result in granuloma formation as a body response leading to osteoporosis. Please vote. The correct answer is C where the polyethylene particles are known to cause macrophage activation and granuloma formation with osteogenesis, metal or metal articulation in figure A usually result in lesions such as pseudotumor or valw or a RMG.
While ceramic on ceramic articulations are biologically inert, linear wear can be measured on X-ray or other special techniques by head penetration in millimeters or millimeters per year. Volumetric wear is measured or calculated in millimeters, cube or millimeters per year. Using simplified equation, assuming that the head produces a cylindrical bowl, many of you will be familiar with this illustration, which shows how much where volume is produced by different combinations of varying surfaces.
It is, however, the size and number of particles which determines the biological effect of the wear debris. Although the volumetric wear is much less a metal or metal articulations, particle size is much smaller slap micron, resulting in billions of particles being produced with each step. Debris production is initially accelerated in the initial wearing in phase, however, it later reduces and reaches a steady state.
Where volume is directly proportionate to the normal load, but and not the stresses and the sliding distance that the articulating surfaces experience, it is inversely proportionate to the hardness of the softer component. Using this information, one can calculate a unitless where coefficient, as well as a more specific wear factor. This is where the disadvantage of Teflon becomes clear.
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