Applied Basic Sciences
Chapter 25 Tribology and biomaterials
📝 Reduction summary (~35% shorter) — high-yield viva edition. All figures & classifications retained; key points bolded for speed reading. Source page badges preserved. Full text: postgradviva2026.pages.dev
source p. 1447
Structured oral examination question 1#
Picture of THA with osteolysis shown.
EXAMINER
This is an X-ray of a THA in an elderly patient complaining of pain. What do you see (Figure 25.1)?
This is an X-ray of a THA in an elderly patient complaining of pain. What do you see (Figure 25.1)?
Figure 25.1a and 25.1b Anteroposterior (AP) and lateral radiographs of hybrid THA with areas of osteolysis around greater trochanter.
CANDIDATE
Plain radiographs of a reverse hybrid THA.
Plain radiographs of a reverse hybrid THA.
EXAMINER
What do you think caused this?
What do you think caused this?
CANDIDATE
Potential causes are infection, poly w ear ...
Potential causes are infection, poly w ear ...
EXAMINER
Tell me about wear.
Tell me about wear.
CANDIDATE
Wear is a progressive loss of material from the surface.
Wear is a progressive loss of material from the surface.
EXAMINER
What types and modes of wear do you know?
What types and modes of wear do you know?
CANDIDATE
Well there are four modes of wear and various types of wear (I couldn’t remember how many). Mode 1:
Well there are four modes of wear and various types of wear (I couldn’t remember how many). Mode 1:
source p. 1448
Mode 2: Wear from an articulating surface and a non-articula.
Mode 3: Third-body wear, which is particles coming.
Mode 4: Wear between non-articula ting surfaces such.
EXAMINER
OK, how about types of wear?
OK, how about types of wear?
CANDIDATE
There are mechanical and chemical. Chemical includes corrosive and corrosive freting.
There are mechanical and chemical. Chemical includes corrosive and corrosive freting.
EXAMINER
Do you know how we can measure wear?
Do you know how we can measure wear?
CANDIDATE
There are linear and volumetric wear which are two methods of measuring wear. For example, the bigger the femoral head the greater the volumetric wear and the smaller ...
There are linear and volumetric wear which are two methods of measuring wear. For example, the bigger the femoral head the greater the volumetric wear and the smaller ...
EXAMINER
Are you sure? Poly has changed over the last 50 years. So, tell me then, what’s the ideal size of a femoral head?
Are you sure? Poly has changed over the last 50 years. So, tell me then, what’s the ideal size of a femoral head?
CANDIDATE
[I was waiting for him to ask me this question, I had some papers in mind and drawings.] McKee and Farrar [1] used large heads and had minimal dislocation but significant wear, Charnley [2,3] initially used size 41.5-mm diameter femoral heads but had massive wear and early failure. He then.
[I was waiting for him to ask me this question, I had some papers in mind and drawings.] McKee and Farrar [1] used large heads and had minimal dislocation but significant wear, Charnley [2,3] initially used size 41.5-mm diameter femoral heads but had massive wear and early failure. He then.
EXAMINER
OK, let’s move on, how does osteolysis happen?
OK, let’s move on, how does osteolysis happen?
CANDIDATE
It’s a histiocytic response to wear debris.
It’s a histiocytic response to wear debris.
EXAMINER
OK, what does that mean?
OK, what does that mean?
CANDIDATE
They release osteolytic factors like TNF-alpha, osteoclast-activ ating factor and interleukins. Also, as the patient walks they release the debris into the effective joint space causing further inflammatory response and lysis [4].
They release osteolytic factors like TNF-alpha, osteoclast-activ ating factor and interleukins. Also, as the patient walks they release the debris into the effective joint space causing further inflammatory response and lysis [4].
source p. 1449
References#
1. McKee GK, Watson-Farrar J. Replacement of arthritic
Surg Br. 1966;48:245–259.
2. present and future developments. 1960;1:821–826.
3. Arthroplasty of the hip. 1961;1:1129–1132.
4. Ing hamE, Fisher J. The role of.
2005;26(11):1271–1286.
source p. 1450
Structured oral examination question 2#
EXAMINER
Tell me about synovial fluid.
Tell me about synovial fluid.
CANDIDATE
Synovial fluid is produced by the synovial membrane in the joint. It is a dialysate of blood plasma without the cloting factors, haemoglobin or RBC. It exhibits non-Newtonian flow characteristics.
Synovial fluid is produced by the synovial membrane in the joint. It is a dialysate of blood plasma without the cloting factors, haemoglobin or RBC. It exhibits non-Newtonian flow characteristics.
EXAMINER
Tell me about lubrication.
Tell me about lubrication.
CANDIDATE
Lubrication is when a film of lo wer shear strength is present between two bearing surfaces, reducing friction.
Lubrication is when a film of lo wer shear strength is present between two bearing surfaces, reducing friction.
EXAMINER
What is friction?
What is friction?
CANDIDATE
The resistance of two surfaces to slide against each other.
The resistance of two surfaces to slide against each other.
EXAMINER
Tell me about the two hypotheses surrounding joint lubrication in synovial joints.
Tell me about the two hypotheses surrounding joint lubrication in synovial joints.
CANDIDATE
The first is fluid-film lubrication, in this hypothesis the joint surfaces are separated by a fluid film which fully supports the applied load, preventing contact between the surfaces. However, realistically, both fluid-film and boundary lubrication occur in synovial joints, depending on the specific joint in question and the particular type of loading applied.
The first is fluid-film lubrication, in this hypothesis the joint surfaces are separated by a fluid film which fully supports the applied load, preventing contact between the surfaces. However, realistically, both fluid-film and boundary lubrication occur in synovial joints, depending on the specific joint in question and the particular type of loading applied.
EXAMINER
Do you know the lambda ratio?
Do you know the lambda ratio?
CANDIDATE
in fluid film it’s 3 and in boundary it’s less than 1.
in fluid film it’s 3 and in boundary it’s less than 1.
EXAMINER
Can you tell me about the different types of fluid-film lubrication?
Can you tell me about the different types of fluid-film lubrication?
CANDIDATE
There are various types of lubrication, the y include hydrodynamic lubrication (HD), elastohydrodynamic (EHD), micro-elastohydrodynamic (MEHD), squeeze film, weeping and boosted lubrication. In hydrodynamic lubrication the reis no contact between the joint surfaces.
There are various types of lubrication, the y include hydrodynamic lubrication (HD), elastohydrodynamic (EHD), micro-elastohydrodynamic (MEHD), squeeze film, weeping and boosted lubrication. In hydrodynamic lubrication the reis no contact between the joint surfaces.
A model that is more likely in synovial joints is elastohydrodynamic (EHD) lubrication. In EHD lubrication elas tic deformation of the bearing surface enlarges the area of the surface and traps pressurized fluid.
A modification of the elas tohydrodynamic model of lubrication is micr o-elastohydrodynamic lubrication (MEHD). This smoothes out the bearing surface and allows a fluid film to be created which is sufficient for fluid-film lubrication.
EXAMINER
Tell me about weeping lubrication.
Tell me about weeping lubrication.
CANDIDATE
Contrary to boosted lubrication where the water is compressed into the cartilage leaving behind a concentrated fluid pooled with hyaluronic acid in the joint.
Contrary to boosted lubrication where the water is compressed into the cartilage leaving behind a concentrated fluid pooled with hyaluronic acid in the joint.
EXAMINER
What are asperities?
What are asperities?
CANDIDATE
the taller they are, the rougher the surface, also increasing friction.
the taller they are, the rougher the surface, also increasing friction.
EXAMINER
OK, what types of lubrication happen in prosthetic joints?
OK, what types of lubrication happen in prosthetic joints?
CANDIDATE
Well, it is believed that boundary lubrication predominates but mixed conditions do occur . For example, ceramics are more hydrophilic than metals, thus they have improved lubrication and lo wer friction ( Figure 25.2).
Well, it is believed that boundary lubrication predominates but mixed conditions do occur . For example, ceramics are more hydrophilic than metals, thus they have improved lubrication and lo wer friction ( Figure 25.2).
Figure 25.2 Lubrication [I drew this picture at the same time].
EXAMINER
OK, so what else decreases friction in the joint?
OK, so what else decreases friction in the joint?
CANDIDATE
The cartilage.
The cartilage.
EXAMINER
So, tell me about cartilage.
So, tell me about cartilage.
CANDIDATE
The cells are chondrocytes and ECM includes fibres, collagen (mainly Type II), elastin, proteoglycans, cartilage oligomeric proteins (COMP) and cartilage matrix protein (CMP).
The cells are chondrocytes and ECM includes fibres, collagen (mainly Type II), elastin, proteoglycans, cartilage oligomeric proteins (COMP) and cartilage matrix protein (CMP).
COMMENT
If you have answered all questions and the y have time the y might ask you a question to fill the 5-minute time. I used the above definition (cells, matrix and water) to answer questions on bonecartilage, meniscus, ligaments and tendon and just changed the cell component and the ECM (i.e.
If you have answered all questions and the y have time the y might ask you a question to fill the 5-minute time. I used the above definition (cells, matrix and water) to answer questions on bonecartilage, meniscus, ligaments and tendon and just changed the cell component and the ECM (i.e.
source p. 1453
Structured oral examination question 3#
source p. 1454
Bone
EXAMINER
What makes up bone?
What makes up bone?
CANDIDATE
Bone is a highly differentiated connective tissue made up of cells (10%) and extracellular matrix 90% (ECM). The ECM contains inorganic and organic matrix, the inorganic matrix includes calcium hydroxyapatite and osteocalcium phosphate. The organic matrix includes collagen Type I, proteoglycans, non-collagen matrix proteins (osteocalcin, osteonectin, os teopontin), growth factors and cytokines. Lamellar bone is mature bone with organized layers and its structure is arranged according to the stress on the bone. Also in flat bones it comprises 80% of the adult bone.
Bone is a highly differentiated connective tissue made up of cells (10%) and extracellular matrix 90% (ECM). The ECM contains inorganic and organic matrix, the inorganic matrix includes calcium hydroxyapatite and osteocalcium phosphate. The organic matrix includes collagen Type I, proteoglycans, non-collagen matrix proteins (osteocalcin, osteonectin, os teopontin), growth factors and cytokines. Lamellar bone is mature bone with organized layers and its structure is arranged according to the stress on the bone. Also in flat bones it comprises 80% of the adult bone.
EXAMINER
Can you draw cortical bone for me (Figure 25.3a)?
Can you draw cortical bone for me (Figure 25.3a)?
Figure 25.3a Drawing of cortical bone.
EXAMINER
Which cell forms the majority of the bone cells?
Which cell forms the majority of the bone cells?
CANDIDATE
The osteocyte forms approximately 90% of bone cells, it forms from osteoblasts.
The osteocyte forms approximately 90% of bone cells, it forms from osteoblasts.
EXAMINER
Tell me about the osteoclasts.
Tell me about the osteoclasts.
CANDIDATE
Osteoclasts are large multinucleated giant cells; When laying on bone they have a contact area called ruffled borders which increase their surface area.
Osteoclasts are large multinucleated giant cells; When laying on bone they have a contact area called ruffled borders which increase their surface area.
Bisphosphonates work on the ruffled borders.
COMMENT
I was drawing something like this as I talked (Figure 25.3b).
I was drawing something like this as I talked (Figure 25.3b).
Figure 25.3b Osteoclast.
EXAMINER
How does the blood reach it?
How does the blood reach it?
CANDIDATE
Bone receives 5–10% of cardiac output. The nutrient artery enters mid diaphysis and divides into ascending and descending branches supplying the inner two-thirds of the cortex.
Bone receives 5–10% of cardiac output. The nutrient artery enters mid diaphysis and divides into ascending and descending branches supplying the inner two-thirds of the cortex.
EXAMINER
How is bone metabolized?
How is bone metabolized?
CANDIDATE
A complex interplay and interaction of various hormones, growth factors and cytokines.
A complex interplay and interaction of various hormones, growth factors and cytokines.
EXAMINER
How does vitamin D regulate calcium?
How does vitamin D regulate calcium?
CANDIDATE
Vitamin D is either taken through diet or activate din the skin by ultraviolet light. In the kidneys it causes increased calcium retention and phosphate excretion ( Figure 25.3c).
Vitamin D is either taken through diet or activate din the skin by ultraviolet light. In the kidneys it causes increased calcium retention and phosphate excretion ( Figure 25.3c).
source p. 1456
Figure 25.3c Vitamin D metabolism.
source p. 1457
Structured oral examination question 4#
source p. 1458
Bone gratis
EXAMINER
So, you have apa tien t with a tibial plateau fracture on your operating t able and you find a big bony defect that needs filling. How do you approach that?
So, you have apa tien t with a tibial plateau fracture on your operating t able and you find a big bony defect that needs filling. How do you approach that?
CANDIDATE
Bearing in mind this is a basic science.
Bearing in mind this is a basic science.
EXAMINER
What types of bone gratis do you know?
What types of bone gratis do you know?
CANDIDATE
There are autogratis, allo gratis and z enogratis. Also , there is demineralized bone matrix (DBM), synthetic, bone morphogenetic protein (BM Pand stem cells. AUTOGRAFT utilizes bone obtained from the same patient receiving it. ALLOGRAFTS are obtained from a different patient than the one receiving it. They are available indifferent methods depending on their processing and preservation, deep fr ozen–70°C, freeze dried –169°C and fresh.
There are autogratis, allo gratis and z enogratis. Also , there is demineralized bone matrix (DBM), synthetic, bone morphogenetic protein (BM Pand stem cells. AUTOGRAFT utilizes bone obtained from the same patient receiving it. ALLOGRAFTS are obtained from a different patient than the one receiving it. They are available indifferent methods depending on their processing and preservation, deep fr ozen–70°C, freeze dried –169°C and fresh.
EXAMINER
What would you use for your case?
What would you use for your case?
CANDIDATE
but I would prefer to use autograft as it has no immunogenicity, but it has donor site morbidity whereas allogratis have no donor site morbidity.
but I would prefer to use autograft as it has no immunogenicity, but it has donor site morbidity whereas allogratis have no donor site morbidity.
EXAMINER
Ahhh, what’s graft incorporation?
Ahhh, what’s graft incorporation?
CANDIDATE
It is the process by which invasion of the graft by the host cells and the graft is then replaced either partially or completely by host bone or rejected. 1. 2. 3. 4. 5. Remodelling, which continues for years.
It is the process by which invasion of the graft by the host cells and the graft is then replaced either partially or completely by host bone or rejected. 1. 2. 3. 4. 5. Remodelling, which continues for years.
EXAMINER
So, we know how an autograft is taken, do you know the process of allograft donation and bone banking?
So, we know how an autograft is taken, do you know the process of allograft donation and bone banking?
CANDIDATE
Yes, living donors are consented and in case of cadavers as longas there.
Yes, living donors are consented and in case of cadavers as longas there.
source p. 1459
The donors get screened for comorbidities and bloods are taken. Bloods for hepatis B & C , HIV, syphilis and Rhesus status.
The graft g oes through processing of cleaning then preservation. The gr aft gets debrided from.
EXAMINER
OK, quickly tell me about the synthetics and what you are going to use for this tibia?
OK, quickly tell me about the synthetics and what you are going to use for this tibia?
CANDIDATE
(I realized I have told him all about bone graft but not t old him what I will use). (JBJS Am 2008) performed an RCT of autograft vs. calcium phosphate cementin tibial plateau fractures and showed significantly reduced rates of subsidence, also Buckley published similar results in 2009 in calcaneal fractures.
(I realized I have told him all about bone graft but not t old him what I will use). (JBJS Am 2008) performed an RCT of autograft vs. calcium phosphate cementin tibial plateau fractures and showed significantly reduced rates of subsidence, also Buckley published similar results in 2009 in calcaneal fractures.
source p. 1460
References#
1. Russell TA, Leighton RK. Comparison of autogenous bone graft and endothermic calcium phosphate.
J Bone Joint Surg Am. 2008;90(10):2057–2061.
2. Johal HS, Buckley RE, Le IL, Leighton RK. A prospective randomized controlled trial
Trauma. 2009;67(4):875–882.
source p. 1461
Structured oral examination question 5#
source p. 1462
THA stem design
EXAMINER
What are these (Figure 25.4a)?
What are these (Figure 25.4a)?
Figure 25.4a Exeter and Charnley femoral stem.
CANDIDATE
The hip replacement on the left is an Ex eter.
The hip replacement on the left is an Ex eter.
EXAMINER
OK. What are the differences between the two?
OK. What are the differences between the two?
CANDIDATE
The Exeter hip replacement is a collarless, polished double-taper cemented hip replacement.
The Exeter hip replacement is a collarless, polished double-taper cemented hip replacement.
EXAMINER
By what biomechanical principles are they supposed to work?
By what biomechanical principles are they supposed to work?
CANDIDATE
The Exeter femoral stem works by utilizing a t aper slip design and controlled subsidence. The stem will subside on average 1.3 mm in the first 2 years, followed by a period of stability. As the stem is loaded the taper engages into the cement, producing radial hoops stress which is distributed to the bone interface minimizing stress shielding.
The Exeter femoral stem works by utilizing a t aper slip design and controlled subsidence. The stem will subside on average 1.3 mm in the first 2 years, followed by a period of stability. As the stem is loaded the taper engages into the cement, producing radial hoops stress which is distributed to the bone interface minimizing stress shielding.
relying on achieving mechanical interlock at the bone–cement interface and sufficient adhesion to achieve force transfer.
The load on the femoral head is transmift ed through the [1].
EXAMINER
What material are they made of?
What material are they made of?
CANDIDATE
The Exeter stem is made of stainless steel alloy (Orthinox), it has high strength with ductility plus.
The Exeter stem is made of stainless steel alloy (Orthinox), it has high strength with ductility plus.
EXAMINER
Which one will you use in your practice and why?
Which one will you use in your practice and why?
CANDIDATE
I will use the Exeter stem based on the theories I mentioned before; also it has excellent survivorship in the NJ Rand a.
I will use the Exeter stem based on the theories I mentioned before; also it has excellent survivorship in the NJ Rand a.
EXAMINER
What is cement?
What is cement?
CANDIDATE
Cement is a synthetic polymer of methyl methacrylate (PMMA). The important factors that affect cement over time are creep, stress relaxation and fatigue. It functions to fill the defect in between the stem and the bone, act for load transfer, allows modulus matching between implant and bone, and in the case of the taper slip stems, allows controlled subsidence of the stem. It is strong in compression and weaker under tension and has a low elastic (Y oung’s) modulus compared to metal and bone.
Cement is a synthetic polymer of methyl methacrylate (PMMA). The important factors that affect cement over time are creep, stress relaxation and fatigue. It functions to fill the defect in between the stem and the bone, act for load transfer, allows modulus matching between implant and bone, and in the case of the taper slip stems, allows controlled subsidence of the stem. It is strong in compression and weaker under tension and has a low elastic (Y oung’s) modulus compared to metal and bone.
EXAMINER
Can you draw the relative moduli on a graph and compare it with other materials used in Orthopaedics (Figure 25.4b)? What is 3, what is 2, what is 11?
Can you draw the relative moduli on a graph and compare it with other materials used in Orthopaedics (Figure 25.4b)? What is 3, what is 2, what is 11?
source p. 1464
Figure 25.4b Diagram stress/strain curve and Young’s modulus.
COMMENT
Figure 25.4b is important as it tests a candidate’s ability to appreciate.
Figure 25.4b is important as it tests a candidate’s ability to appreciate.
EXAMINER
What are the design principles behind the use of uncemented joint replacements?
What are the design principles behind the use of uncemented joint replacements?
CANDIDATE
The uncemented joint replacement can be put in in two ways. The first is a press-fit design, the secondis a line-to-line fixation. In line-to-line fixation, the bone is prepared to be the same size as the eventual implant, e.g. A cup the same size as the prepared acetabulum is inserted but, in this case, additional fixation, such as screws, is frequently required.
The uncemented joint replacement can be put in in two ways. The first is a press-fit design, the secondis a line-to-line fixation. In line-to-line fixation, the bone is prepared to be the same size as the eventual implant, e.g. A cup the same size as the prepared acetabulum is inserted but, in this case, additional fixation, such as screws, is frequently required.
EXAMINER
What can you tell me about the surface finish of the implant?
What can you tell me about the surface finish of the implant?
CANDIDATE
The surface finish allows either bony ingrowth or ongrowth. Ingrowth requires a pore size between 50 and 400 μm, and the percentage of voids within the coating should be between 30% and 40% to maintain mechanical strength.
The surface finish allows either bony ingrowth or ongrowth. Ingrowth requires a pore size between 50 and 400 μm, and the percentage of voids within the coating should be between 30% and 40% to maintain mechanical strength.
EXAMINER
Do you know anything about the design of the pores?
Do you know anything about the design of the pores?
CANDIDATE
The porosity of the stem should not be greater 50%.
The porosity of the stem should not be greater 50%.
EXAMINER
How do stems fail?
How do stems fail?
source p. 1465
CANDIDATE
The cemented stems fail in four modes: 1a. 1b. 2. Medial stem pivot. 3. 4. Cantilever bending.
The cemented stems fail in four modes: 1a. 1b. 2. Medial stem pivot. 3. 4. Cantilever bending.
EXAMINER
Do you know any name associated with this classification?
Do you know any name associated with this classification?
CANDIDATE
Sorry. Gruen’s mode of cemented femoral stem failure.
Sorry. Gruen’s mode of cemented femoral stem failure.
source p. 1466
Reference#
‘Modes of failure’ of cemented stem-type femoral components: 1979;141:17–27.
EXAMINER
And the uncemented stems?
And the uncemented stems?
CANDIDATE
Delamination of the HA coating , there is also a mechanism known as flag-staffing. If a relatively small stem is inserted in apa tien t.
Delamination of the HA coating , there is also a mechanism known as flag-staffing. If a relatively small stem is inserted in apa tien t.
source p. 1467
References#
1. ShenG. Femoral stem fixation. An engineering interpretation of the long-t erm.
2. The Exeter Universal cemented femoral stem at 20 to 25 years: 2016;98B(11):1441–1449.
source p. 1468
Structured oral examination question 6#
source p. 1469
Articular cartilage
EXAMINER
What do you see (Figure 25.5)?
What do you see (Figure 25.5)?
Figure 25.5 Knee arthroscopy picture focal area of cartilage loss.
CANDIDATE
This is a picture of a knee arthroscopy showing a grade IV cartilage defect.
This is a picture of a knee arthroscopy showing a grade IV cartilage defect.
EXAMINER
What is cartilage?
What is cartilage?
CANDIDATE
The cells are chondrocytes, and the ECM includes fibres, collagen (mainly Type II), elastin, proteoglycans, cartilage oligomeric proteins (COMP) and cartilage matrix protein (CMP).
The cells are chondrocytes, and the ECM includes fibres, collagen (mainly Type II), elastin, proteoglycans, cartilage oligomeric proteins (COMP) and cartilage matrix protein (CMP).
EXAMINER
Draw a cross-section of cartilage.
Draw a cross-section of cartilage.
CANDIDATE
I drew all layers, superficial, middle and deep, arcades of Benninghoff, the tidemark and calcific zone.
I drew all layers, superficial, middle and deep, arcades of Benninghoff, the tidemark and calcific zone.
EXAMINER
What is the importance of the tidemark?
What is the importance of the tidemark?
CANDIDATE
The tidemark is the boundary between the calcified and uncalcified cartilage made visible by histological staining.
The tidemark is the boundary between the calcified and uncalcified cartilage made visible by histological staining.
EXAMINER
What is the importance of water in cartilage?
What is the importance of water in cartilage?
CANDIDATE
70% of articular cartilage is water; 30% of it exists between the collagen fibres and this is determined by the negative charge of the proteoglycans (PG) which lie within the collagen matrix. Because the PG are bound closely the closeness of the negative charges creates a repulsion force that must be neutralized by positive ions (hydrogen ions in water) in the surrounding fluid.
70% of articular cartilage is water; 30% of it exists between the collagen fibres and this is determined by the negative charge of the proteoglycans (PG) which lie within the collagen matrix. Because the PG are bound closely the closeness of the negative charges creates a repulsion force that must be neutralized by positive ions (hydrogen ions in water) in the surrounding fluid.
EXAMINER
What happens in osteoarthritis?
What happens in osteoarthritis?
CANDIDATE
The collagen network is disrupted either by trauma or an increase in degradation enzymes concentration – this allows the proteoglycans to atir act more water and softens the articular cartilage thus.
The collagen network is disrupted either by trauma or an increase in degradation enzymes concentration – this allows the proteoglycans to atir act more water and softens the articular cartilage thus.
EXAMINER
OK, so how will you treat this defect? [Going back to the arthroscopy picture.]
OK, so how will you treat this defect? [Going back to the arthroscopy picture.]
CANDIDATE
This is grade IV on the Outerbridge Arthroscopic Grading System. Using the hookas a reference, it measures.
This is grade IV on the Outerbridge Arthroscopic Grading System. Using the hookas a reference, it measures.
EXAMINER
How would you do that?
How would you do that?
CANDIDATE
The goal is to allow access of marrow.
The goal is to allow access of marrow.
source p. 1471
I would prepare the defect until I achieved stable vertical walls and the calcified cartilage layer was removed.
3–4 mm apart, looking for the fat droplets.
Postoperatively patients are allowed protected weight-bearing.
If that defect was larger than 4 cm2
however, I will refer this patient to a knee surgeon expert in this field. I’m also aware.
EXAMINER
Would you do an ACI?
Would you do an ACI?
CANDIDATE
Well, NICE does recommend it, but it has strict criteria and it has to be done at
Well, NICE does recommend it, but it has strict criteria and it has to be done at
source p. 1472
Structured oral examination question 7#
source p. 1473
Fracture fixation
EXAMINER
Tell me about your approach to the fixation of this fracture (Figure 25.6a).
Tell me about your approach to the fixation of this fracture (Figure 25.6a).
Figure 25.6a Anteroposterior (AP) radiograph of the left knee demonstrating tibial plateau fracture.
CANDIDATE
First, I would assess the patient the soft tissue and.
First, I would assess the patient the soft tissue and.
EXAMINER
Yes, yes, there are no tricks in this question everything is fine with the patient this is a question about the biomechanics of fracture fixation.
Yes, yes, there are no tricks in this question everything is fine with the patient this is a question about the biomechanics of fracture fixation.
CANDIDATE
Right, OK, this is a plain radiograph of a comminuted displaced, intra-articular fracture of the tibial plateau. The principles regarding the fixation of this fracture are anatomical reduction and absolute stability of the articular.
Right, OK, this is a plain radiograph of a comminuted displaced, intra-articular fracture of the tibial plateau. The principles regarding the fixation of this fracture are anatomical reduction and absolute stability of the articular.
EXAMINER
Tell me about how you would achieve a stable fixation of the articular surface.
Tell me about how you would achieve a stable fixation of the articular surface.
CANDIDATE
I would then use 6.5-mm partially threaded cancellous screws to act as both a subchondral raft and also to compress the fracture fragments and achieve absolute stability and primary bone healing.
I would then use 6.5-mm partially threaded cancellous screws to act as both a subchondral raft and also to compress the fracture fragments and achieve absolute stability and primary bone healing.
EXAMINER
Why do you want to achieve absolute stability?
Why do you want to achieve absolute stability?
CANDIDATE
The lack of movement means that the osteoclasts involved in the remodelling of bone will essentially ignore the fracture site and proceed directly across the fracture site using cuting cones, therefore healing by primary bone healing without the formation of callus.
The lack of movement means that the osteoclasts involved in the remodelling of bone will essentially ignore the fracture site and proceed directly across the fracture site using cuting cones, therefore healing by primary bone healing without the formation of callus.
EXAMINER
How does a screw work?
How does a screw work?
CANDIDATE
A screw converts rotational movement into longitudinal advancement. With a lag screw, the screw is partially threaded therefore as the distal threads bite in the fracture fragment, the proximal smooth barrel.
A screw converts rotational movement into longitudinal advancement. With a lag screw, the screw is partially threaded therefore as the distal threads bite in the fracture fragment, the proximal smooth barrel.
EXAMINER
What are the parts of the screw?
What are the parts of the screw?
COMMENT
It is easy to draw and illustrate (Figure 25.6b).
It is easy to draw and illustrate (Figure 25.6b).
Figure 25.6b Design features of orthopaedic screw.
EXAMINER
You said you will use a cancellous screw. What is the main difference between a cancellous and acor tical screw?
You said you will use a cancellous screw. What is the main difference between a cancellous and acor tical screw?
CANDIDATE
Pitch, core to outer diameter and tip. Pitch: closely spaced threads incor tical screws with smaller pitch compared with deeply cut.
Pitch, core to outer diameter and tip. Pitch: closely spaced threads incor tical screws with smaller pitch compared with deeply cut.
source p. 1475
Tip: cortical screws are blunt.
EXAMINER
You mentioned you will use your plate in bridging mode, what other modes do you know?
You mentioned you will use your plate in bridging mode, what other modes do you know?
CANDIDATE
But iress, bridging, compression, tension band, neutralization.
But iress, bridging, compression, tension band, neutralization.
EXAMINER
So why would you use this one in bridging mode?
So why would you use this one in bridging mode?
CANDIDATE
If the other features of length, axis and rotation are correct then the fracture would be expected to heal by secondary bone healing with callus formation.
If the other features of length, axis and rotation are correct then the fracture would be expected to heal by secondary bone healing with callus formation.
EXAMINER
What do you understand by Perren’s strain theory?
What do you understand by Perren’s strain theory?
CANDIDATE
Strain is defined as change in length over original length. The theory suggests that the mechanical environment (strain) governs the type of tissue that is laid down between the fracture fragments. Granulation tissue can.
Strain is defined as change in length over original length. The theory suggests that the mechanical environment (strain) governs the type of tissue that is laid down between the fracture fragments. Granulation tissue can.
EXAMINER
Describe the stages of fracture healing.
Describe the stages of fracture healing.
CANDIDATE
The stages are haematoma and inflammation, soft callus (1 week to months), hard callus (1– 4 months) and then remodelling (years). In the first stage, haematoma forms and provides key cells such as macrophages, key inflammatory cytokines (IL1, IL6, TGF-β) are secreted and eventually haematoma is replaced with granulation tissue. Once the fracture has united the final phase of remodelling happens where hard callus is remodelled from woven bone to hard, dense, lamellar bone by the process of osteoclastic resorption followed by osteoblastic bone formation.
The stages are haematoma and inflammation, soft callus (1 week to months), hard callus (1– 4 months) and then remodelling (years). In the first stage, haematoma forms and provides key cells such as macrophages, key inflammatory cytokines (IL1, IL6, TGF-β) are secreted and eventually haematoma is replaced with granulation tissue. Once the fracture has united the final phase of remodelling happens where hard callus is remodelled from woven bone to hard, dense, lamellar bone by the process of osteoclastic resorption followed by osteoblastic bone formation.
EXAMINER
What factors influence fracture healing?
What factors influence fracture healing?
CANDIDATE
Two key factors are involved, mechanical environment and biology. Local factors such as open or closed injury, high mechanism, bone loss, site and type of bone.
Two key factors are involved, mechanical environment and biology. Local factors such as open or closed injury, high mechanism, bone loss, site and type of bone.
source p. 1476
Structured oral examination question 8#
source p. 1477
Osteoporosis
EXAMINER
Could you define osteoporosis for me please?
Could you define osteoporosis for me please?
CANDIDATE
In 1993 WHO defined osteoporosis as a systemic skeletal disease characterized by low bone mass and deterioration in the microarchitecture, leading to enhanced bone fragility and a consequent increase in fracture risk. It is considered normal when the bone mineral density is within 1 standard deviation of the mean peak bone mass of a healthy 25-year-old. Osteopenia when it is 1–2.5 below the mean and osteoporosis when it is> 2.5 below the mean. Type 1 is most common in women after menopause.
In 1993 WHO defined osteoporosis as a systemic skeletal disease characterized by low bone mass and deterioration in the microarchitecture, leading to enhanced bone fragility and a consequent increase in fracture risk. It is considered normal when the bone mineral density is within 1 standard deviation of the mean peak bone mass of a healthy 25-year-old. Osteopenia when it is 1–2.5 below the mean and osteoporosis when it is> 2.5 below the mean. Type 1 is most common in women after menopause.
EXAMINER
How does a DEX Ascan work?
How does a DEX Ascan work?
CANDIDATE
DEX Ascan is dual-energy X-ray absorptiome try used to assess bone mineral density (BM DIt involves the use of two X-ray beams of different energies passed through the neck of femur or lumbar spine (L2–L4). The result is then compared to a sex- and race-matched BMD of a healthy young adult population (25–30) producing a T score.
DEX Ascan is dual-energy X-ray absorptiome try used to assess bone mineral density (BM DIt involves the use of two X-ray beams of different energies passed through the neck of femur or lumbar spine (L2–L4). The result is then compared to a sex- and race-matched BMD of a healthy young adult population (25–30) producing a T score.
EXAMINER
This is a DEX Ascan report (Figure 25.7), how would you interpret it?
This is a DEX Ascan report (Figure 25.7), how would you interpret it?
source p. 1478
Figure 25.7 DEX Ascan report for proximal femur and lumbar spine.
COMMENT
You are expected to know how to interpret a DEX Ascan report. Simplifying it, I just concentrated on the T score and explained that the risk of fracture approximately doubles for each standard deviation decrease inT score. It depends on what the score is, you then can define it as normal/osteopenia or osteoporosis. 1. 2. 3. 4. T score.
You are expected to know how to interpret a DEX Ascan report. Simplifying it, I just concentrated on the T score and explained that the risk of fracture approximately doubles for each standard deviation decrease inT score. It depends on what the score is, you then can define it as normal/osteopenia or osteoporosis. 1. 2. 3. 4. T score.
EXAMINER
How would you manage this patient?
How would you manage this patient?
CANDIDATE
Prior to obtaining the DEX Ascan I would have performed an initial work up which includes detailed history, examination and bloods. In the history I will.
Prior to obtaining the DEX Ascan I would have performed an initial work up which includes detailed history, examination and bloods. In the history I will.
I would also use the FRAX tool which computes 10-year.
Treatment will be according to the NOGG [3] and NICE guidelines [4].
If the patient is at risk or has confirmed OP, then I would provide them with information regarding lifestyle changes. Lifestyle measures to improve bone health include increasing the.
(www.shef.ac.uk/FRAX)
EXAMINER
How much calcium and Vit D do you give them?
How much calcium and Vit D do you give them?
CANDIDATE
In postmenopausal women and older men (> 50 years) at increased risk of fracture a daily dose of 800 IU cholecalciferol should be advised. In postmenopausal women and older men receiving bone-protectiv e.
In postmenopausal women and older men (> 50 years) at increased risk of fracture a daily dose of 800 IU cholecalciferol should be advised. In postmenopausal women and older men receiving bone-protectiv e.
EXAMINER
Which pharmacological treatment would you choose?
Which pharmacological treatment would you choose?
CANDIDATE
Alendronate 70 mg once-weekly or Risedronate are first-line treatments in the majority of cases.
Alendronate 70 mg once-weekly or Risedronate are first-line treatments in the majority of cases.
EXAMINER
How do bisphosphonates work?
How do bisphosphonates work?
CANDIDATE
The nitrogen group inhibits protein prenylation with an end result of loss of guanosine triphosphatase (GTPase) formation, this is needed for ruffled border formation and cell survival. The nitrogen-lacking bisphosphonates are metabolized into a non-functional adenosine triphosphate (ATP) analogue, which induces cell apoptosis.
The nitrogen group inhibits protein prenylation with an end result of loss of guanosine triphosphatase (GTPase) formation, this is needed for ruffled border formation and cell survival. The nitrogen-lacking bisphosphonates are metabolized into a non-functional adenosine triphosphate (ATP) analogue, which induces cell apoptosis.
source p. 1480
References#
1. Kanis JA, Gluer CC. An update on.
Commift ee of Scientific Advisors, International Osteoporosis Foundation.
2. Kanis JA, McCloskey EV, Johansson HO den A, Melton LJ, 3rd, Khaltaev N.
3. National Osteoporosis Guideline Group (NOGG). 2017.
4. NICE guidelines:
Compston J, Cooper A, Cooper C, et al. Guidelines for the diagnosis and management of.
Compston J, Bowring C, Cooper A, et al. Diagnosis and management of osteoporosis in.
2013;75:392–396.
source p. 1481
Structured oral examination question 9#
source p. 1482
Antibiotic prophylaxis
EXAMINER
Which antibiotic do you use for infection prophylaxis in arthroplasty?
Which antibiotic do you use for infection prophylaxis in arthroplasty?
CANDIDATE
Our hospital policy recommends cefuroxime 1.5 g at induction provided that.
Our hospital policy recommends cefuroxime 1.5 g at induction provided that.
EXAMINER
How does cefuroxime work?
How does cefuroxime work?
CANDIDATE
Cefuroxime is a beta lactam antibiotic; it inhibits the cr oss-linking of polysaccharides in.
Cefuroxime is a beta lactam antibiotic; it inhibits the cr oss-linking of polysaccharides in.
EXAMINER
Could you tell me about other antibiotics you know and their mechanism of action?
Could you tell me about other antibiotics you know and their mechanism of action?
CANDIDATE
In general, I divide the antibiotics by their mechanism of action to antibiotics working on.
In general, I divide the antibiotics by their mechanism of action to antibiotics working on.
Figure 25.8 Simple bacterium (I drew a simple bacterium which is available in most books).
EXAMINER
How do the bacteria develop resistance?
How do the bacteria develop resistance?
CANDIDATE
Bacteria can develop resistance either by intrinsic resistance or by acquired resistance to antibiotics. Bacteria can develop the ability to hydrolyze the.
Bacteria can develop resistance either by intrinsic resistance or by acquired resistance to antibiotics. Bacteria can develop the ability to hydrolyze the.
EXAMINER
How does MRSA develop resistance?
How does MRSA develop resistance?
CANDIDATE
MRSA develops resistance through a gene called mecA, it produces the enzyme penicillin- binding protein 2a (PBP2a). 20% of patients are staph carriers and 5% are MRSA carriers. Patients must have three negative samples before considering joint arthroplasty.
MRSA develops resistance through a gene called mecA, it produces the enzyme penicillin- binding protein 2a (PBP2a). 20% of patients are staph carriers and 5% are MRSA carriers. Patients must have three negative samples before considering joint arthroplasty.
Carriers are treated with nasal mucopirocin and 4% chlorhexedine.
EXAMINER
How do you prevent infections in your department?
How do you prevent infections in your department?
CANDIDATE
laminar flow theatres, minimize theatre traffic, prophylactic IV antibiotics within 1 hour of incision, antibiotic-loaded cement shaving at time of surgery, good hand-washing technique, draping with disposable drapes and ioband, opening of sets within the laminar flow, efficient surgery, good haemostasis and sound wound closure and avoid hypothermia throughout the procedure. however, this is debatable depending on departmental policies, early mobilization and physiotherapy, optimal medical management, timely but safe discharge.
laminar flow theatres, minimize theatre traffic, prophylactic IV antibiotics within 1 hour of incision, antibiotic-loaded cement shaving at time of surgery, good hand-washing technique, draping with disposable drapes and ioband, opening of sets within the laminar flow, efficient surgery, good haemostasis and sound wound closure and avoid hypothermia throughout the procedure. however, this is debatable depending on departmental policies, early mobilization and physiotherapy, optimal medical management, timely but safe discharge.
source p. 1484
Structured oral examination question 10#
source p. 1485
Theatre suite
EXAMINER
How would you design a theatre suite?
How would you design a theatre suite?
CANDIDATE
When designing a theatre suite, the first important aspect is theatre location, it needs to beclose to related facilities such as ITU , A&E, Surgical wards, and Radiology. Outer zone: Clean zone: Disposal zone: sluices (Figure 25.9). Lights should be satellite with 40,000 lux at the wound site. Optimum temperature for the patient is 25°C and for the staff is 19°C. We aim to create a microclimate for the patient to prevent hypothermia by using Bair huggers, warmed mat iress and fluids ...
When designing a theatre suite, the first important aspect is theatre location, it needs to beclose to related facilities such as ITU , A&E, Surgical wards, and Radiology. Outer zone: Clean zone: Disposal zone: sluices (Figure 25.9). Lights should be satellite with 40,000 lux at the wound site. Optimum temperature for the patient is 25°C and for the staff is 19°C. We aim to create a microclimate for the patient to prevent hypothermia by using Bair huggers, warmed mat iress and fluids ...
source p. 1486
Figure 25.9 Disposal zone. Four zones: outer zone, clean zone, aseptic z one and disposal zone. The purpose of having zones is to have defined boundaries.
EXAMINER
Which ventilation system is used in your department?
Which ventilation system is used in your department?
CANDIDATE
We have theatres with a laminar flow ventilation system.
We have theatres with a laminar flow ventilation system.
EXAMINER
What is laminar flow?
What is laminar flow?
CANDIDATE
It is a system that produces an entire body of air flowing in one direction with uniform velocity and.
It is a system that produces an entire body of air flowing in one direction with uniform velocity and.
EXAMINER
Tell me about the ex-flow Howarth system
Tell me about the ex-flow Howarth system
CANDIDATE
[I had no idea, the only thing I could remember was a trumpet type of airflow.
[I had no idea, the only thing I could remember was a trumpet type of airflow.
EXAMINER
OK, tell me about the vertical laminar flow.
OK, tell me about the vertical laminar flow.
CANDIDATE
Vertical laminar flow was introduced by Charnley and is the most common type used. It creates a room within a room, with panels from the ceiling to 2 m from the floor. It filters particles of 0.5 μm with 99.9% efficiency.
Vertical laminar flow was introduced by Charnley and is the most common type used. It creates a room within a room, with panels from the ceiling to 2 m from the floor. It filters particles of 0.5 μm with 99.9% efficiency.
source p. 1487
EXAMINER
Does it filter viruses?
Does it filter viruses?
CANDIDATE
Umm, no.
Umm, no.
EXAMINER
What are the advantages and disadvantages of horizontal vs. vertical laminar flow?
What are the advantages and disadvantages of horizontal vs. vertical laminar flow?
CANDIDATE
Horizontal is easier to install, but positioning of staff and equipment is restricted because of the sideways flow of air. Vertical laminar flow does not restrict staff and.
Horizontal is easier to install, but positioning of staff and equipment is restricted because of the sideways flow of air. Vertical laminar flow does not restrict staff and.
EXAMINER
What are the sources of infection theatres?
What are the sources of infection theatres?
CANDIDATE
Patient surgeon, instruments and airborne.
Patient surgeon, instruments and airborne.
EXAMINER
How do you measure bacterial contamination in the air?
How do you measure bacterial contamination in the air?
CANDIDATE
By slit samplers called Casel lait draws in air over 1 minute which passes overculture plates, which are then incubated over 48 hours and colonies formed are counted. It is measured in.
By slit samplers called Casel lait draws in air over 1 minute which passes overculture plates, which are then incubated over 48 hours and colonies formed are counted. It is measured in.
EXAMINER
Do you think laminar flow prevents joint infection?
Do you think laminar flow prevents joint infection?
CANDIDATE
I believe it is a combination of multiple factors. Results of the MRC trial in 1982 (Lidwell et al.) published in BMJ showed that deep sepsis in arthroplasty was reduced significantly by the use of antibiotic-loaded cement prophylactic IV antibiotics peri operatively, laminar flow and body exhaust suits [1]. Charnley also showed a reduction in deep.
I believe it is a combination of multiple factors. Results of the MRC trial in 1982 (Lidwell et al.) published in BMJ showed that deep sepsis in arthroplasty was reduced significantly by the use of antibiotic-loaded cement prophylactic IV antibiotics peri operatively, laminar flow and body exhaust suits [1]. Charnley also showed a reduction in deep.
source p. 1488
References#
1. Lidwell OM, Lowbury EJ, Why teW, Blowers R, Stanley SJ, LoweD. Effect of ultra clean air in operating.
1982;285:10–14.
2. Charnley J. Postoperative infection after total hip replacement with special reference.
3. Hooper GJ, Rothwell AG, Frampton C, Wyatt MC. The ten-year results of the New Zealand Joint
Registry. J Bone Joint Surg Br. 2011;93(1):85–90.
source p. 1489
Structured oral examination question 11#
source p. 1490
VTE
EXAMINER
How do you set up a VTE protocol in your department?
How do you set up a VTE protocol in your department?
CANDIDATE
I would set up a protocol to assess all elective and trauma patients. Risk assessment will be performed using a published tool or guidelines such as the NICE guidelines to balance their risks of VTE against bleeding. They will be stratified in to a low-risk group or a high-risk group. The low-risk group will be offered mechanical prophylaxis only and the high-risk group will be offered both mechanical and pharmacological prophylaxis suitable for them.
I would set up a protocol to assess all elective and trauma patients. Risk assessment will be performed using a published tool or guidelines such as the NICE guidelines to balance their risks of VTE against bleeding. They will be stratified in to a low-risk group or a high-risk group. The low-risk group will be offered mechanical prophylaxis only and the high-risk group will be offered both mechanical and pharmacological prophylaxis suitable for them.
EXAMINER
What are the current guidelines for elective hip replacement?
What are the current guidelines for elective hip replacement?
CANDIDATE
The guidelines will be changing in 2018 and aspirin will be considered; however, the current guidelines suggest starting mechanical prophylaxis at admission, either anft-embolism stocking or intermift ent pneumatic compression devices. This should continue un.
The guidelines will be changing in 2018 and aspirin will be considered; however, the current guidelines suggest starting mechanical prophylaxis at admission, either anft-embolism stocking or intermift ent pneumatic compression devices. This should continue un.
EXAMINER
What are the guidelines for total knee replacement and how do they differ from total hip replacements?
What are the guidelines for total knee replacement and how do they differ from total hip replacements?
CANDIDATE
It is the same protocol, but the duration is shorter 10–14 days.
It is the same protocol, but the duration is shorter 10–14 days.
EXAMINER
OK, what is the new guideline that is coming up?
OK, what is the new guideline that is coming up?
CANDIDATE
In the new guidelines it is recommended to offer VTE prophylaxis to people undergoing elective hip replacement surgery. LMWH (for 10 days) followed by aspirin (for 28 days). LMWH (for 28 days) combined with anft-embolism stockings (until discharge).
In the new guidelines it is recommended to offer VTE prophylaxis to people undergoing elective hip replacement surgery. LMWH (for 10 days) followed by aspirin (for 28 days). LMWH (for 28 days) combined with anft-embolism stockings (until discharge).
EXAMINER
And for knees?
And for knees?
CANDIDATE
Offer VTE prophylaxis to people undergoing elective knee replacement surgery.
Offer VTE prophylaxis to people undergoing elective knee replacement surgery.
source p. 1491
LMWH (for 14 days) combined with anft-embolism stockings.
Rivaroxaban.
Consider intermift ent pneumatic compression if pharmacological prophylaxis is contraindicated in people.
EXAMINER
Is there a role for chemical prophylaxis inpatient’s lower limb immobilization?
Is there a role for chemical prophylaxis inpatient’s lower limb immobilization?
CANDIDATE
The new guidelines suggest considering pharmacological VTE prophylaxis for people undergoing foot or ankle surgery, in particular: When total anaesthesia time is greater than 1 hour.
The new guidelines suggest considering pharmacological VTE prophylaxis for people undergoing foot or ankle surgery, in particular: When total anaesthesia time is greater than 1 hour.
EXAMINER
What is the mechanism of action of LMWH, aspirin and Riv aroxaban?
What is the mechanism of action of LMWH, aspirin and Riv aroxaban?
CANDIDATE
It also prevents formation oft her omboxane A2, which is a prothrombotic agent secreted by platelets. If you have time you can draw the intrinsic and extrinsic pathways and explain where each drug works (Figure 25.10).
It also prevents formation oft her omboxane A2, which is a prothrombotic agent secreted by platelets. If you have time you can draw the intrinsic and extrinsic pathways and explain where each drug works (Figure 25.10).
Figure 25.10 Intrinsic and extrinsic cloting pathway .