Exam Corner

Hip & Knee Arthroplasty

Prepared by Asif Parkar  

 

Questions

  1. Patients who have hip pain in the first 3 months after hip arthroplasty with no radiographic evidence of dislocation or periprosthetic fracture must be evaluated for infection. For such patients the most specific and sensitive method to diagnose early infection is:

    1. nuclear medicine bone scan

    2. serial radiographs

    3. SPECT CT

    4. joint aspiration

    5. inflammatory markers ESR & CRP
       

  2. Osteolysis occurs if linear wear rate exceeds:

    1. 0.01 mm/year

    2. 0.1 mm/year

    3. 1.0 mm/year

    4. 10 mm/year

    5. 0.2mm/year
       

  3. The following are risks for nerve injury during hip arthroplasty except:

    1. lengthening > 3.5 cm

    2. post traumatic arthritis

    3. males

    4. revision surgery

    5. developmental dysplasia of hip
       

  4. Heel strike represents which of the following types of lubrication:

    1. Boundary lubrication

    2. Hydrodynamic lubrication

    3. Squeeze film lubrication

    4. Weeping lubrication

    5. Boosted lubrication
       

  5. Which of the following bearing surface combinations exhibits the ability to polish out isolated surface scratches also known as self healing:

    1. ceramic on ceramic

    2. metal on metal

    3. ceramic on poly

    4. metal on poly

    5. all of the above
       

  6. The synergistic combination of wear and corrosion of two materials in contact causing micromotion between the two, such as seen in the morse taper, is an example of:

    1. Galvanic corrosion

    2. Crevice corrosion

    3. Fretting corrosion

    4. Pitting corrosion

    5. Stress corrosion
       

  7. Hip fusion increases the energy expenditure to mobilise by approximately:

    1. 15%

    2. 30%

    3. 45%

    4. 60%

    5. 75%
       

  8. Stress shielding effect seen in uncemented femoral stems is best explained by:

    1. Wolff’s law

    2. Hueter Volkmann law

    3. Hooke’s law

    4. Hoek’s law

    5. Young’s modulus law
       

  9. In a hip replacement, which of the following modes of failure is associated with proximal loss of stem support while distally the stem is securely fixed:

    1. Pistoning of the stem within the cement

    2. Pistoning of the stem within bone

    3. Medial mid stem pivot

    4. Calcar pivot

    5. Cantilever bending
       

  10. Cracking of the femoral cement mantle occurs if the mantle is:

    1. less than 2 mm

    2. less than 3 mm

    3. less than 4 mm

    4. less than 5 mm

    5. less than 6 mm
       

  11. Which of the following is not a contraindication for osteotomy in varus arthritic knees:

    1. inflammatory arthropathy

    2. flexion contracture over 10 degrees

    3. lateral tibial subluxation > 1 cm

    4. cruciate ligament insufficiency

    5. joint narrowing of lateral compartment
       

  12. Which of the following is not a contraindication for unicompartmental knee arthroplasty:

    1. inflammatory arthropathy

    2. flexion contracture more than 10 degrees

    3. correctable deformity in coronal plane

    4. previous menisectomy in the opposite compartment

    5. ACL deficiency in a mobile bearing knee
       

  13. A PCL sacrificing knee replacement is used in all of the following except:

    1. inflammatory arthropathy

    2. post patellectomy

    3. severe deformity

    4. MCL deficiency

    5. attenuation of the PCL
       

  14. Which of the following is not an indication for a hinged knee replacement:

    1. global instability

    2. hyperextension instability

    3. neuropathic joint

    4. osteonecrosis of the knee

    5. massive infection needing several revisions
       

  15. The minimum thickness of the patella to allow revision of a patellar resurfacing is:

    1. 10 mm

    2. 12 mm

    3. 14 mm

    4. 16 mm

    5. 18 mm
       

  16. Which of the following is not an established technique to determine femoral component rotation:

    1. anteroposterior axis method

    2. epicondylar axis method

    3. posterior condylar axis method

    4. gap balancing method

    5. patellar tracking assessment method
       

  17. Which of the following is the most recent and so far the best method of manufacturing polyethylene:

    1. ram bar extrusion

    2. calcium stearate addition

    3. compression moulding with machine

    4. direct compression moulding without machine

    5. sheet moulding
       

  18. All of the following are associated with higher risk of infection except:

    1. rheumatoid arthritis

    2. neuropathic joints

    3. diabetic patients

    4. oral steroid use

    5. obesity
       

  19. Patellar clunk occurs during active extension in certain posterior cruciate sacrificing designs of a knee replacement.  The nodule responsible for this is located at the:

    1. distal end of the patellar tendon

    2. proximal end of the patellar tendon

    3. distal end of quadriceps tendon

    4. proximal end of quadriceps tendon

    5. distal pole of the patella
       

  20. The recommended order for removal of implants during revision knee replacements is:

    1. tibial poly, femoral component, tibial component, patella

    2. tibial poly, tibial component, femoral component, patella

    3. patella, femoral component, tibial poly, tibial component

    4. patella, tibial poly, tibial component, femoral component

    5. femoral component, tibial poly, tibial component, patella

       

Answers:

  1. d) joint aspiration
    Joint aspiration must be considered during the work up for infected arthroplasty. Combination of CRP and ESR has the 2nd best sensitivity and specificity.
    Reference: Core knowledge in Orthopaedics – Adult reconstruction & Arthroplasty, Jonathan Garino, P - 125

  2. b) 0.1 mm / year
    Reference: Miller sixth edition, P – 373

  3. c) male
    Females are at higher risk of developing nerve injury during hip replacement compared to males.
    Reference: Miller sixth edition, P – 375

  4. c) squeeze film lubrication
    Factors affecting lubrication include radial clearance, surface roughness, bearing size and surface properties. There are 2 main types of lubrication, Boundary and Fluid film based on the lambda ratio. There are no subtypes of boundary lubrication. Fluid film is mainly seen in synovial joints and has several types, Squeeze film being one of them, and is mainly seen at heel strike.
    Reference: Basic Orthopaedic Sciences, The Stanmore guide, 1st edition P – 222

  5. b) metal on metal
    Amongst the available bearing surfaces only metal on metal has the ability to self heal and self polish the micro uneven surfaces after the initial bedding in period.
    Reference: Basic Orthopaedic Sciences, The Stanmore guide, 1st edition P – 233

  6. c) fretting corrosion
    Corrosion from the micromotion between two surfaces in contact damages the protective film and the classic example of this is the corrosion at the taper.
    Reference: Basic Orthopaedic Sciences, The Stanmore guide, 1st edition P – 235

  7. b) 30%
    Walking with a fused hip 30% more energy consumption.
    Reference: Miller sixth edition  P –360

  8. d) Hoek’s law
    When two materials are loaded in a similar setting more force is transmitted through the stiffer material and this is called Hoek’s law. The linear relationship between stress and strain over the linear portion of the graph is called Hooke’s law.
    Reference: Miller sixth edition,  P –366 & Basic Orthopaedic Sciences, The Stanmore guide, 1st edition P – 147

  9. e) cantilever bending
    This can happen with both cemented and uncemented stems and is more common in thin stems.
    Reference:Miller sixth edition,  P –368 & Basic Orthopaedic Sciences, The Stanmore guide, 1st edition P – 168

  10. a) less than 2 mm
    In cemented stems a minimum of 2 mm of cement mantle should be kept around the stem and it is particularly important at the proximal medial end of the femur.
    Reference: Core knowledge in Orthopaedics – Adult reconstruction & Arthroplasty Jonathan Garino, P- 125

  11. d) cruciate ligament insufficiency
    Multi ligament or collateral ligament deficiencies are contraindications for a valgus producing osteotomy. An isolated ACL or PCL deficiency is not.
    Reference: Miller sixth edition, P –393

  12. c) correctable deformity in coronal plane
    Only fixed deformities or severe deformities should not be considered for unicompartmental knee replacements.
    Reference: Miller sixth edition,  P –393

  13. d) MCL deficiency
    MCL deficiency is not treated with PCL sacrificing knee as this needs a more constrained hinge replacement.
    Reference: Miller sixth edition, P –403

  14. d) osteonecrosis of the knee
    Spontaneous osteonecrosis of the knee (SONK) is not an indication for a hinged knee replacement.
    Reference: Miller sixth edition, P –403

  15. b) 12 mm
    Reference: Miller sixth edition,  P –408

  16. e) patellar tracking assessment method
    Do not implant the femoral component in internal rotation. Care must be taken to avoid this error particularly in valgus knees as this affects patellar tracking.
    Reference: Miller sixth edition, P –410

  17. d) direct compression moulding without machining
    This has shown the least wear amongst the different manufacturing techniques.
    Reference: Miller sixth edition, P–385 & 415

  18. b) neuropathic joints
    Reference: Core knowledge in Orthopaedics – Adult reconstruction & Arthroplasty, Jonathan Garino, P- 151

  19. c) distal end of quadriceps tendon
    Patellar clunk incidence has declined significantly with recent TKR designs
    Reference: Core knowledge in Orthopaedics – Adult reconstruction & Arthroplasty, Jonathan Garino, P- 152

  20. a) tibial poly, femoral component, tibial component, patella
    This sequence provides more exposure for the next stage of the procedure.
    Reference: Revision Total Hip & Knee Arthroplasty, D Berry, P - 470