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You are welcome to attempt these questions whether you are attending the course or not. If you are attending the next BBiOrth course we recommend that you that you should try to go through these questions before the course.

Please do not be concerned if you find that you are unfamiliar with the material - this would all be covered during the course. You may consult the course book and other sources to answer the questions. The questions are mainly to prepare you for what would be covered on the day.

1. The moment of a force is the effect of a force at:

An oblique distance from a pivot
%
A perpendicular distance from a pivot
%
A defined magnitude
%
A Synovial joint
%
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A moment of force is the effect of a force at a perpendicular distance from an axis, which results in rotational movement and angular acceleration.
Text Book

Further reading

Pages 6-7

2. The orthopaedic surgeon has a responsibility for:

Choice of implants
%
Assembly and positioning of implants
%
Mobilisation of patient
%
All of the above
%
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The orthopaedic surgeon has a responsibility to understand materials and structural limitations of orthopaedic devices and principles of their applications to minimise failure.
Text Book

Further reading

Pages 2-3

3. The biomechanical goal of a total knee replacement is to:

Preserve the level of the joint line
%
Balance the ligaments
%
Make the bone cuts perpendicular to the mechanical axis
%
All of the above
%
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In addition, the mechanical axis of the lower limb should be restored so that it passes through the centres of the hip, knee and ankle. Rigid, durable fixation should be achieved. Restoring the mechanical alignment prevents a net varus or valgus force, which causes uneven contact pressure on the polyethylene and early failure. It also prevents instability and pain through unbalanced ligaments.
Text Book

Further reading

Pages 124-125

4. Which loading mode produces a butterfly fragment-type fracture?

Compression
%
Bending
%
Torsion
%
Tension
%
Next
A butterfly fragment-type fracture is classically produced by a bending force. A compression force typically produces an oblique fracture; a tensile force produces a transverse fracture; a torsional force produces a spiral fracture. 20 May 2017
Text Book

Further reading

Pages 66-67

5. The bending rigidity of a rod (e.g. intramedullary nail) is proportional to its:

Radius, r2
%
Radius, r3
%
Radius, r4
%
Radius, r5
%
Next
Clinically, when using intra-medullary nails for long bone fracture treatment, we aim to use the largest diameter nail possible (without breaking the cortex of the bone further). Intra-medullary reaming helps to enlarge the medullary cavity to allow easy passage of the nail.
Text Book

Further reading

Pages 56-57 and 176-177

6. The ‘tension band’ fixation of fractures:

Converts two distracting forces into compressive forces
%
Converts two shear forces into compressive forces
%
Converts two torsional forces into compressive forces
%
All of the above
%
Next
Examples of fractures that can be fixed with tension band mechanism are: Olecranon (distracting force = triceps), patella (distracting force = quadriceps muscles and patella tendon), greater and lesser tuberosity fractures of the humerus (distracting force = rotator cuff muscles) and greater trochanter fracture of the femur (distracting force = abductor muscle group).
Text Book

Further reading

Pages 166-167

7. Tribology is the study of friction, wear and lubrication. Biotribology is the application of tribology to biological systems. Friction between two surfaces in relative motion (e.g. bearing surfaces of joints) depends on all of the following factors except:

Load
%
Lubricant
%
Roughness of surfaces
%
Contact area between two surfaces and sliding speed
%
Next
Friction is a force that resists relative movement between two surfaces in contact. Friction occurs because no surface is absolutely smooth at molecular scale, and asperities i.e. microscopic projections, on one surface interact with asperities on the opposite surface to resist motion. Static friction is the force required to initiate motion and dynamic friction is the force required to maintain motion between contacting surfaces. Friction is always parallel to contacting surfaces and opposite to direction of motion.
Friction equation: Friction [N] = μ x Load [N]
Friction does not depend on contact area and sliding speed of the two surfaces.
Text Book

Further reading

Pages 82-83

8. Which imaging modality can be used to investigate for prostheses loosening?

Plain film
%
Bone scan
%
MRI
%
All of the above
%
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All of these modalities can be used to assess loosening of prosthesis, depending on the clinical setting,although there are benefits and downsides to each modality.

9. Force is a vector quantity. It has:

Magnitude
%
Magnitude and direction
%
Magnitude, point of application and line of action
%
Magnitude, point of application, line of action and sense
%
Next
Consider the example of a football: The displacement of football due to the applied force depends on the magnitude (how much), sense (upwards/ forwards), point of application (where on the football force makes the contact) and the line of action of applied force.
Text Book

Further reading

Pages 4-5

10. A material is a physical substance used to make objects. There are four basic groups of materials. Which of the following is NOT a basic group of materials:

Metals
%
Alloys
%
Polymers
%
Composites
%
Next
There are four groups of materials: metals, ceramics, polymers and composites. Materials in each group have similar molecular structure and therefore exhibit similar range of properties. An alloy is a substance that is composed of two or more elements, at least one of which is a metal, united by dissolving in each other when molten e.g. brass is an alloy of zinc in copper.
Text Book

Further reading

Pages 24-25

11. In total hip replacement surgery, ‘medialising’ the acetabular component has the following effect on the joint reaction force:

Increase
%
Decrease
%
Change direction
%
No effect
%
Next
The hip joint acts as the fulcrum of a class I lever system (like a see-saw). The joint reaction force is the product of the effect of the abductor muscle force and body weight acting on the opposite sides of this fulcrum. Appropriately medialising the acetabular component increases the lever arm of abductor muscle force and decreases the lever arm of the body weight. This has the overall effect of decreasing the joint reaction force (and therefore wear of the components).
Text Book

Further reading

Pages 106-107

12. Immature bones in children have different mechanical properties to mature bones in adults. Therefore, there are variations in fractures patterns in children. A buckle fracture in an immature bone is produced by which mode of loading?

Compression
%
Tension
%
Bending
%
Torsion
%
Next
A compressive load can produce a torus or ‘buckle’ fracture in children. This type of fracture typically occurs in the metaphyseal region of long bones. Immature cortical bone is more porous and less dense than mature bone, and so is weak under compressive stress. Therefore, bone cortex under compressive load sustains a local fracture that does not propagate to the opposite cortex because of bone ductility.
Text Book

Further reading

Pages 68-69

13. The bending rigidity of a plate is proportional to its:

Thickness, t2
%
Thickness, t3
%
Thickness, t4
%
Thickness, t5
%
Next
The bending stiffness of a plate is proportional to its width and to its thickness to the power to the third.
Text Book

Further reading

Pages 56-57 and 172-173

14. Following fracture union, the decision was made to remove a metal plate. How should the patient be mobilised after plate removal? The patient has previously been fully bearing weight.

Immediate full weight-bearing
%
Non weight-bearing
%
Partial weight-bearing
%
None of the above
%
Next
The relative stiffness or modulus of bone versus metallic plate is an important consideration in fracture healing under conditions of internal fixation. The higher stiffness and strength of the metal plate relative to bone in a bone/plate reconstruction results over time in a well-recognised bony resorption under the plate known as stress- shielding or plate-induced osteopenia. Therefore, when removing plates, the bone must be gradually re-introduced to weight-bearing loads. Impact forces are to be avoided.
Text Book

Further reading

Pages 72-73

15. Which of the following pair of surfaces has the lowest coefficient of friction:

Metal on metal
%
Ice on ice
%
Cartilage on cartilage
%
Teflon on Teflon
%
Next
Contacting surfaces Typical coefficient of friction
Metal on metal (dry)0.41
Metal on metal (lubricated)0.06
Teflon on Teflon0.04
Ice on ice0.03
Cartilage on cartilage0.005
Text Book

Further reading

Pages 82-83

16. On plain films, the lowest threshold of periprosthetic lucency to suggest prosthesis loosening is:

1mm
%
2mm
%
4mm
%
5mm
%
Next
Perisprosthetic lucency up to 2mm can be considered normal if patient is asymptomatic.

17. What are the units of measurement of strain?

Metre (m)
%
Newton per square metre (Nm-2)
%
None
%
Centimetre (cm)
%
Next
A material’s deformation (e.g. elongation) can be measured as change in length per unit initial length. This is known as normal strain and is a dimensionless unit.
Text Book

Further reading

Pages 16-17

18. Stainless steel is an alloy that contains all of the following elements except:

Chromium
%
Cobalt
%
Iron
%
Carbon
%
Next
Steel is an iron-carbon alloy. Stainless steel is iron-carbon alloy that also contains chromium and sometimes nickel. Stainless steel can also contain minor quantities of other important elements, such as manganese, molybdenum and sulphur. Stainless steel has a high resistance to corrosion when compared to plain steel – this is a function of chromium and nickel.
Text Book

Further reading

Pages 30-31

19. What would be the effect of reducing offset when performing a THR?

Reduce abductor moment arm
%
Reduce joint reaction force
%
Increase abductor moment arm
%
I don’t know
%
Next
The offset can be defined as the perpendicular distance from the centre of the femoral head to the long axis of the femur. The abductor moment arm is measured from the greater trochanter (abductor insertion) to the centre of the femoral head. As offset is increased, the abductor moment arm is lengthened and vice versa. Theoretically, increasing the abductor moment arm increases the efficiency of the abductors therefore reducing the joint reaction force. The converse is true if the abductor moment arm is shortened as in reducing offset.
Text Book

Further reading

Pages 106-107

20. Although fatigue fracture is an uncommon cause of bone failure, it is the most common cause of failure of engineering structures. Fatigue strength and fatigue life of a structure are related to:

Stress amplitude (fluctuations in load levels during a loading cycle)
%
Number of ‘stress raisers’
%
Frequency of loading
%
All of the above
%
Next
Fatigue strength and fatigue life are affected by stress amplitude, number of stress raisers and frequency of loading.
Text Book

Further reading

Pages 64-65

21. The following are all examples of different designs of screws, except:

Lag screw
%
Self-tapping screw
%
Locking screw
%
Cannulated screw
%
Next
A ‘lag screw’ is not a design of screw but instead is the mode in which a screw is applied. Any screw can theoretically be applied as a lag screw.
Text Book

Further reading

Pages 170-171

22. Three-point fixation in the treatment of fractures:

Is often used to control fractures following plate fixation
%
Is seldom required following effective fracture manipulation
%
Involves a force acting over a fracture site and two forces acting opposite to the first, proximal and distal to the fracture
%
Causes a force couple
%
Next
Three-point fixation should be performed following fracture manipulation. A force over the fracture opposes the deforming force. The two other opposite-directed forces ‘the third hand’, helps prevent a force couple (turning effect of two equal opposite forces).
Text Book

Further reading

Pages 164-165

23. In total hip replacement, increasing the diameter of femoral head leads to the following effects, except:

Increased friction
%
Increased frictional torque
%
Increased primary arc of motion
%
Increased jump distance (i.e. the distance the femoral head has to jump before it is dislocated)
%
Next
The lager diameter femoral head is more stable because it has a better primary arc of motion and requires a greater jump distance before dislocation. The friction at the articulating surface remains the same, as friction is independent of contact area and sliding speed. However, a larger diameter femoral head leads to a greater frictional torque.
Text Book

Further reading

Pages 108-109

24. Peri-prosthetic bony periosteal reaction:

Is a sign of prosthesis loosening
%
Is a sign of prosthesis infection
%
Can be a normal finding
%
All of the above
%
Next
Peri prosthetic bony periosteal reaction is a non-specific sign and can be either a positive sign or negative sign depending on the patient's clinical state.

25. Which physical property of the bone is the most significant to its biomechanical function?

Strength
%
Stiffness
%
Hardness
%
Toughness
%
Next
Without ‘stiff’ bones, humans would be crawling on the ground with strong, hard and tough skeletons. The stiffness of the bones keeps the skeleton upright.
Text Book

Further reading

Pages 46-47

26. The following are examples of some commonly used biomaterials in orthopaedics. Which of these is NOT a polymer?

Plaster of Paris
%
Bone cement
%
Polydioxanon (PDS) suture
%
Polyethylene components for total hip replacement prostheses
%
Next
The commonly used plaster of Paris for closed treatment of fractures is a composite of a fabric bandage, the reinforcemet phase, impregnated with gypsum cement, the matrix phase. The gypsum cement forms a paste when mixed with water and hardens into a solid to form the required splints and casts. The new synthetic cast materials are also composites that consist of fibreglass in polymetric matrix.
Text Book

Further reading

Pages 42-43

27. The majority of complications after a total knee replacement operation are related to:

The femoral component
%
The tibial component
%
The patello-femoral joint
%
None of the above
%
Next
The majority of complications after TKR are related to patella tracking. One of the goals of TKR is to ensure proper soft tissue balance and correct patella tracking.
Text Book

Further reading

Pages 124-125

28. Traction is the method of realigning a fractured bone by applying a tensile force to the affected limb. Which of the following statements about tract is incorrect?

It works on the principles of ligamentotaxis
%
The function of the applied force is to produce tension in the soft tissues
%
Traction by gravity is a routinely used method for managing proximal humerus fractures
%
Traction can only be generated by application of longitudinal force(s) to the limb
%
Next
Traction can be produced by application of two perpendicular forces e.g. a balanced traction.
Text Book

Further reading

Pages 160-161

29. A plate can be applied to the bone in a number of different modes. In which mode is the plate usually at the greatest risk of fatigue failure?

Neutralisation mode
%
Compression mode
%
Tension mode
%
Bridging mode
%
Next
A plate applied in bridging mode is at an increased risk of fatigue failure because the bone-plate construct is likely to be less stable than in other modes due to fracture characteristics e.g. comminution, bone loss or poor quality bone, which may also lead to impaired bone healing.
Text Book

Further reading

Pages 174-175

30. Fractures of the clavicle are most common in the middle third because:

The attached muscles apply excessive forces to this region
%
This region is most exposed to injury
%
The middle section of the clavicle has the smallest cross-sectional area
%
Fractures in the other regions often go un-noticed
%
Next
The middle third of clavicle has the smallest cross-sectional area, and is relatively unsupported compared to the ends of the clavicle. It is therefore most prone to failure, and approximately 80% of clavicular fractures occur in this section.
Text Book

Further reading

Pages 188-189

31. There are three modes of lubrication. Which mode leads to least wear of the articulating surfaces?

Boundary lubrication
%
Mixed lubrication
%
Fluid film lubrication
%
I don’t know
%
Next
Fluid film lubrication is the ultimate in minimising wear between two interacting surfaces.
Text Book

Further reading

Pages 86-87

32. In a knee MRI scan, the normal meniscus appear:

Bright on T1 and T2 weighted images.
%
Dark on T1 and T2 weighted images.
%
Bright on T1 but dark on T2 weighted images
%
Dark on T1 but bright on T2 weighted images
%
Next
Meniscus is fibrocartilage which contains no water or fat and therefore dark on T1 and T2 weighted imaging. High signal within meniscus indicates abnormality.

33. Which of the following mechanical properties can NOT be directly derived from the stress-strain curve of a material?

Stiffness
%
Hardness
%
Toughness
%
Strength
%
Next
Hardness describes the material’s resistance to localised surface plastic deformation e.g. scratch or dent. Hardness is not a basic mechanical property, but instead is derived from a combination of other mechanical properties e.g. stiffness and strength. Hardness determines wear resistance of a material. Therefore, a harder material has a higher wear resistance and lower surface wear than a softer material under the same loading conditions.
Text Book

Further reading

Pages 20-21

34. Which of the following is NOT a mechanical property of ceramics:

Bioactivity (i.e. interactions with biological tissues)
%
High strength in tensile loading
%
Very high hardness
%
Brittleness
%
Next
Ceramics are strong in compression but weak in shear and tension. This is because ceramics contain impurities and defects under normal conditions. These act to amplify stress and therefore reduce the overall strength of the material. Stress amplification occurs mainly in shear and tension, but not in compression – compression in fact closes defects and reduces the overall number of imperfections in the material. Therefore, ceramics are about ten times as strong in compression as in tension. This makes them good materials for application in structures under pure compression e.g. bricks and stone blocks in buildings.
Text Book

Further reading

Pages 32-33

35. When ascending stairs, the tibiofemoral joint reaction force is approximately

x 2 Total body weight
%
x 3 Total body weight
%
x 4 Total body weight
%
x 5 Total body weight
%
Next
The tibiofemoral joint reaction force increases sharply with knee flexion. It is the resultant vector of the ground reaction force and quadriceps force. A commonly used example to illustrate the peak forces produced in the tibiofemoral joint is during ascending stairs. The typical height of a step of stairs is 20cm, which requires about 60° of knee flexion during the single leg stance period of the gait cycle. The static analysis shows that tibiofemoral joint reaction force is about five times total body weight.
Text Book

Further reading

Pages 118-119

36. A functional brace:

Immobilises the fracture
%
Does not rely on the stiffness of the bracing material, but instead on set volume of cylinder formed
%
Produces tensile force across the fracture
%
Prevents the muscles from contracting
%
Next
The functional brace works by creating a cylinder of set volume around the limb. When the muscles contract, their attempted increase in size produces a hydraulic compressive force that stabilizes the fracture. Therefore, a functional brace stabilizes, but does not immobilize, the fracture. Although the fracture ends are relatively mobile, they return to the original position because the compressive force is uniformly distributed within the cylinder. The principle of soft tissue containment does not depend on the stiffness of the bracing material, but instead on the set volume of the cylinder formed.
Text Book

Further reading

Pages 192-193

37. A pin-to-bar external fixator consists of three components: pins, clamps and bars. Which of the three components is the least stiff (and therefore limits the rigidity of bone-frame construct)?

Pins
%
Clamps
%
Bars
%
I don’t know
%
Next
A pin is technically a screw that protrudes out of the skin. It is the least stiff of the three components. The weakest point within the pin is the thread-shank junction.
Text Book

Further reading

Pages 182-183

38. The majority of humeral shaft fractures are managed conservatively. However, some humeral shaft fractures require operative fixation. The two primary methods of operative fixation of humeral shaft fractures are IM nailing and plate fixation. Regarding plate fixation:

It is a load-sharing implant.
%
IM nail is preferred over plate for fixing humeral shaft fractures
%
There is a greater rick of fracture non-union with plate fixation than IM nail fixation
%
There should ideally be a minimum of six cortices’ fixation on either side of the fracture.
%
Next
A plate is the gold standard for surgical fixation of humeral shaft fractures. It is a load bearing implant. Fracture configuration dictates the mode in which the palate is applied. A transverse fracture can be fixed with direct compression plating; a short oblique or a spiral fracture may be stabilized with lag screws with the plate applied in neutralization mode; and, in comminuted fractures, the plate is applied in bridging mode. The use of locking plates is advantageous in the setting of poor bone quality but not in fracture comminution per sa. There should ideally be a minimum of six cortices’ fixation on either side of the fracture.
Text Book

Further reading

Pages 192-193

39. In total hip replacement, the likelihood of achieving fluid film lubrication between bearing surfaces depends on:

Material of bearing surfaces
%
Diameter of femoral head
%
Radial clearance
%
All of the above
%
Next
‘Metal on metal’ and ‘ceramic on ceramic’ surfaces support fluid film lubrication. The likelihood of achieving fluid film lubrication increases as the femoral head diameter increases. There must be radial clearance between the femoral head and acetabular cup to allow fluid to move in between the articulating surfaces.
Text Book

Further reading

Pages 92-93

40. Which one of these is correct?

Normal ACL on MRI excludes ACL tear
%
Signal change in meniscus on MRI indicates symptomatic tear
%
Signal change in MCL indicates ligamentous tear
%
None of the above
%
Next
Normal ACL on MRI does not exclude tear and therefore it is important to recognise the indirect signs. Only high signal within the meniscus that extends to the articular surface on MRI should be considered 'true tear'. Normal ligaments on MRI are of dark signal and high signal change indicates injury.
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