Abstract
Biomechanics Structured SBA Questions
Biomechanics Structured SBA Questions
1. When stabilising a middiaphyseal femoral fracture using an intramedullary nail, locking bolts are passed proximal and distal to the fracture.
The main function of these locking bolts is which of the following?
2. Which of the following forms of synovial joint lubrication is most important in prolonged stance?
3. A surgeon implants a cemented stainless steel femoral stem during a total hip arthroplasty. In error, the surgeon then applies a cobalt-chrome head to the trunnion before reducing and closing the hip.
What mechanism of corrosion could have been avoided if a stainless steel head had been used?
4. A cobalt-chrome head and a ceramic femoral head are being tested in a lab. During one test, a sharp object is run along each material’s surface. The size and depth of the resultant scratch is assessed.
What material property is being tested for in this scenario?
5. During the manufacturing process of cross-linked UHMWPE, vitamin E is added to the polymer.
What is the primary role of vitamin E in cross-linked UHMWPE?
6. An implant company are designing a new uncemented femoral stem. They decided to use a titanium alloy, as its Young’s modulus is significantly lower than a stainless steel option.
A lower Young’s modulus is advantageous in this case because of which of the following?
8. A surgeon doing a total hip replacement decides to use a larger diameter femoral head to reduce the risk of future dislocation.
How does increasing head diameter most improve hip stability?
9. A surgeon inserting a femoral broach into a tight femoral canal decides to pause between each strike of the hammer for 10 seconds in order to reduce the risk of femoral fracture.
Which of the following viscoelastic features best explains the surgeon’s logic?
10. A surgeon wishes to maximise the stability of a total hip replacement by increasing the primary arc range of motion, and thus reducing the risk of impingement.
Which of the following does NOT increase the primary arc?
11. What is the most important mechanism of wear leading to osteolysis in a metal-on-polyethylene total hip joint bearing surface?
12. A metal is being tested for its material properties in a laboratory by undergoing cyclical loading, with increasing loads on each cycle. It is noted once loads are applied that exceed the material’s yield point, the stress required to cause further plastic deformity goes up with each loading cycle.
Which of the following best describes the cause for this phenomenon?
13. In Ponseti casting, a moulded plaster applies a constant stress to the soft tissues of the foot and ankle. Over a period of time, this constant stress results in a gradual correction of the deformity.
Which viscoelastic material property is being demonstrated in this treatment?
15. The primary role of the femoral and tibial stems in a hinged knee replacement is to do which of the following?
16. An uncemented total hip replacement is being revised for aseptic loosening. On extraction it is noted there is significant backside wear of the polyethylene.
Which of McKellop’s modes of wear is best described in this case?
17. Cross-linking in polymers is known to increase material strength and stiffness.
Which type of bond is formed between long monomer chains during cross-linking?
20. A block of PMMA cement is being tested for its response to different loads.
With regard to the mechanical properties of PMMA cement, which of the following statements is correct?
21. Fluid-film lubrication can significantly reduce wear in prosthetic joints.
Which type of total hip bearing design is most likely to allow fluid-film lubrication?
22. An implant engineer is trying to design a hard-on-hard bearing surface for a THR that achieves hydrodynamic fluid-film lubrication.
Which of the following will most help increase the probability of them achieving this?
23. A patient with cuff arthropathy is offered a reverse-polarity shoulder replacement.
Which of the following statements is NOT true in reverse shoulder replacements (RSA)?
RSA allows some of the fibres from the anterior and posterior deltoid to act as shoulder abductors
24. Figure 25.1 shows the stress–strain curves for three different materials.
Figure 25.1 Stress–strain curve
Regarding this chart, which of the following statements is true?
25. Figure 25.2 shows a schematic diagram of fracture fixed with a plate.
Figure 25.2 Plate fixation fracture
Which letter corresponds to the working length of the plate?
27. A 9-year-old boy sustains a transverse femoral fracture, which is being managed with elastic nails.
All of the following are important principles in maintaining a balanced construct in elastic stable intramedullary nailing (ESIN) EXCEPT which?
28. A surgeon wants to achieve primary bone healing of a fracture.
Which of the following methods of plate fixation will NOT aid primary bone healing?
29. A surgeon fixes a Weber B lateral malleolar fracture using a lag screw and a one-third tubular plate in neutralisation mode.
What is the primary role of a neutralisation plate?
30. Figure 25.3 demonstrates an S–N curve for a metal.
Figure 25.3 S–N curve
What does point A represent?
31. Which of the following will NOT affect the bony integration of hydroxyapatite (HA) coated implants for total hip replacement?
32. You are required to fill a bone defect in a weight bearing region. The defect is 2cm and has a healthy soft tissue cover.
Which of the following is the most appropriate?
33. You are performing a long femoral nail in a 70-year-old for a subrochanteric fracture. The distal tip of the nail is short, sitting proximal to the metaphysis.
Why might this cause an issue?
34. You are asked to design an ideal plate for fracture fixation.
Which one of the following properties would you want to avoid in the design?
35. Why as patients get older does the femur expand?
With an increase in radius, the same torsional rigidity can be achieved with the less cortical bone
36. A patient has had a safety external fixator applied following a knee dislocation and postoperatively is sent for an MRI. The MRI radiographer rings up to say the half pins are stainless steel and therefore the patient can’t have the MRI.
Is the radiographer correct?
No, ask the radiographer to use a 1.5 Tesla MRI rather than the standard 3T and it will be safe to proceed
37. 316L steel is used in many orthopaedic applications.
It contains chromium to give it which property?
Related posts:
Chapter 6 – Knee II Structured SBA
Chapter 7 – Foot and Ankle Structured SBA
Chapter 20 – Pathology I Structured SBA
Chapter 24 – Prosthetics and Orthotics Structured SBA
Chapter 26 – Clinical Environment, Evidence Management and Quality Improvement Structured SBA
Chapter 15 – Hand II Structured SBA
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