Arthroplasty (2008-2019)

Question 1

1. When standing on one leg, what is the hip joint reaction force?
2. 2.5
3. 4.5
4. 6.5
5. 8.5

Answer 1

ANSWER: A

2012, 2013

• Journal of Biomechanics (2001) - Hip contact forces and gait patterns from routine activities
  
  • The average peak forces of the patients during normal walking at about 4km/h were between 211and 285% bodyweight.

Question 2

2.When are you more likely to injure the superior gluteal nerve?

1. Glut med split with Hardinge approach
2. Retractor placement with Kocher Langenbach
3. When doing a GT osteotomy

Answer 2

ANSWER: A

2012

Question 3

3. What is the most common nerve injury associated with the Hardinge approach for a THA?
   a. Sciatic
   b. Inferior gluteal
   c. Superior gluteal
   d. Femoral

Answer 3

ANSWER: C

2015

• Picado CH (CORR 2007) Damage to the superior gluteal nerve after direct lateral approach to the hip

Question 4

4. The most common nerve injured during THA is:
5. Sciatic (peroneal division)
6. Obturator
7. Superior Gluteal Nerve
8. Femoral Nerve

Answer 4

ANSWER: A

2013

JAAOS 1999 - Nerve Injuries in THA

• Abitbol JJ (J Arthroplasty 1990) Gluteal nerve damage following THA
• Subclinical gluteal nerve injury documented in over 77% of patients

Question 5

5. Sciatic nerve in THA. All of the following except:
6. Most completely recover
7. 70% have subclinical EMG changes
8. more common in females
9. more common in revisions

Answer 5

ANSWER: A

2009

Farrell CM (JBJS 2005) Motor nerve palsy following primary THA

• Risk factors for nerve palsy –> DDH, post-traumatic arthritis, posterior approach, lengthening of extremity, cementless fixation
• Only 36% had complete recovery at 21 months
• 7/18 patients with incomplete palsy fully recovered their strength

JAAOS 1999 - Nerve Injuries in THA

• 70% of THA had subclinical sciatic nerve injury
• Mentions women as potential risk
• Isolated peroneal division did well, but very poor recovery if both tibial and peroneal divisions involved
• More frequent in DDH and revision scenario

Question 6

6. When putting in screws into the acetabulum and going into the safe posterosuperior zone, what is at risk?
7. Obturator NV bundle
8. External iliac
9. Superior gluteal
10. Inferior gluteal

Answer 6

ANSWER: C

Question 7

7. In order to determine the acetabular safe zone for screw placement, a line is drawn from where to where?
8. AIIS to center of acetabulum
9. ASIS to center of acetabulum
10. Ischial tuberosity to center of acetabulum
11. Cannot remember the last option

Answer 7

ANSWER - B

2014

• Wasielewski RC (JBJS 1990) Acetabular anatomy and the transacetabular fixation of screws in total hip arthroplasty.
  
  • The quadrants are formed by drawing a line from the anterior superior iliac spine through the center of the acetabulum to the posterior fovea, forming acetabular halves. A second line is then drawn perpendicular to the first at the mid-point of the acetabulum, forming four quadrants. The posterior superior and posterior inferior acetabular quadrants contain the best available bone stock and are relatively safe for the transacetabular placement of screws. The anterior superior and anterior inferior quadrants should be avoided whenever possible, because screws placed improperly in these quadrants may endanger the external iliac artery and vein, as well as the obturator nerve, artery, and vein. The acetabular-quadrant system provides the surgeon with a simple intraoperative guide to the safe transacetabular placement of screws during primary and revision acetabular arthroplasty.

Question 8

8. 3rd generation cement technique does not include which of the following
9. Vacuum mixing PMMA
10. Pressurized
11. Use of a cement plug
12. Retrograde filling

Answer 8

ANSWER: C/D

2013

• Confusing – other version said pressurized mixing which is wrong
• Cement plug and retrograde (cement gun) filling were introduced in the 2nd generation but still part of 3rd generation.
•  AAOS Comprehensive Review States:
• First-generation femoral cement techniques: cement mixed by hand in an open bowl; cement placed in canal by hand; no canal lavage or drying; pressure provided by surgeon’s thumb
• Second-generation techniques: plug, injecting doughy cement, using a cement gun
• Third-generation techniques: porosity reduction with vacuum, pressurization, pulsatile lavage

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3880950/#bib23 Bone Cement – J Clin Orthop Trauma 2013 – doi 10.1016/j.jcot.2013.11.005

Orthobullets: Technique

cementing techniques have evolved with time

1st generation

• hand-mixed cement
• finger packed cement
• no canal preparation or cement restrictor

2nd generation

• cement restrictor placement
• cement gun
• femoral canal preparation
• brush and dry

3rd generation

• vacuum-mixing to reduce cement porosity
• cement pressurization
• femoral canal preparation
• pulsatile lavage

*** 4th generation is an even cement mantle using centralizers for the stem

The well cemented THA p 150-154 Heisel 2005

Question 9

9. When pre-op planning for a THA, the femoral mechanical axis is?
10. A line drawn through the centre of the femoral head to 1.5 cm medial to center of knee
11. A line drawn through the centre of the femoral head to 1.5 cm lateral to center of knee
12. A line drawn through the centre of the femoral head and intersecting the anatomic axis at the intercondylar notch
13. A line bisecting the medullary canal

Answer 9

ANSWER: C

2014

• C correctly describes the mechanical axis of the femur, some argument for D in planning of a THA specifically

Question 10

10. What is a disadvantage of HXPE vs UHMWPE:
11. Decreased fracture
12. Decreased oxidization
13. Increased cost
14. Decreased wear - advantage

Answer 10

ANSWER: C

2015

• Thomas GE (JBJS 2011) The seven-year wear of highly cross-linked polyethylene in total hip arthroplasty: a double-blind, randomized controlled trial using radiosterometric analysis
• XHPE has significantly lower steady-state wear than conventional ultra-high molecular weight polyethylene
• Sakellariou V (HSS J 2013) Highly cross-linked polyethylene may not have an advantage in TKA
• We concluded that:
  
  • the material properties of XLPE reduce adhesive and abrasive wear, but not the risk of crack propagation, deformation, pitting, and delamination found in TKR
  • wear-induced osteolysis in TKR has not been found to be a major cause of failure at long-term follow-up
  • mid-term follow-up studies show no difference in any recorded outcome measure between conventional PE and XLPE
  • XLPE is two to four times the cost of conventional PE without an improvement in clinical or radiographic outcomes.
• Bhandari - Evidence Based Orthopedics
  
  • Short duration follow up
  • Improvement in wear with HXPE
  • Mechanical properties of HCLPE are negatively affected by crosslinking

Question 11

11. Regarding the mechanical axis in the tibia, all are true except?
12. Colinear and parallel in coronal plane
13. Colinear and parallel in sagittal plane
14. Mechanical and anatomical tibia axes are colinear
15. LE axis passes 8 mm medial to tibial spines

Answer 11

ANSWER: D

2008

• 8mm is way to medial – variable but wither centre or slight medial
• Orthobullets: MAT (mech axis of tibia) is from central prox tibia to central talus, same as AAT (anatomic axis of tibia)
• Cherian et al. 2014: The position of the mechanical axis causes it to usually pass just medial to the tibial spine, but this can vary widely based on the patient height and pelvic width (increased pelvic width as in females and decreased height results in increased axis deviation

Question 12

12. What can be expected following trochanteric advancement which creates relative neck lengthening?
13. Abductor weakness
14. Reduces trendelenberg gait
15. Will cause a limp
16. Increased joint reaction forces

Answer 12

ANSWER: B

2016

• Usually aim to distalize and lateralize to improve abductor moment arm
• Aim is to tension abductors, increase stability (in THA) or improve function/ decrease tredelenburg
• Yes, it increases compressive forces (see millers pic) in general = increased instability
• But technically increases offset (lateralize) and decrease JRF, no clear evidence evaluating JRF and Troch advancement but lots saying that it helps with hip function.

Question 13

1. 13. Metal on poly total hip. What is the most common cause of wear?
2. Mode 1
3. Mode 2
4. Mode 3
5. Mode 4

Answer 13

ANSWER: A

2011

JBJS 1999 - Current Concepts Review: Wear in Total Hip and Knee Replacements

• Mode 1 - motion between one primary bearing surface and another (head on liner)
• Mode 2 - primary bearing surface articulates with non-bearing surface (Head on shell)
• Mode 3 - entrapped abrasive particles between bearings
• Mode 4 - motion at secondary surfaces (impingement/fretting/backside wear)

Question 14

14. Stability of THA reduced by?
15. larger head
16. smaller head
17. troch bursitis secondary to altered soft tissue tension
18. position of cup at 40 degrees inclination and 15 degrees anteversion

Answer 14

ANSWER: B

2011

• decreased jump distance

Question 15

15. Which articulation has the least wear?
16. large head metal on metal
17. small head metal on metal
18. head on crosslinked poly
19. ceramic on ceramic

Answer 15

ANSWER: D

2011, 2012