CH62- TKR

Question 1

• What is the biomedtrix TKR system (constrained vs semi?)

Answer 1

• semi-constrained

Question 2

• What is the indication for cementless tibia component? Cemented?

Answer 2

• Cemented - suboptimal bone quality
• Ie, advanced age, chronic disuse osteopenia, concurrent disease

Question 3

• What are 3 most common reasons for failure of implant?

Answer 3

• Infection
• Collateral ligament disruption
• Aseptic loosening

Question 4

• What are contraindications for TKR in the dog

Answer 4

• Infection
• Retained iplants → remove min. 6 wks prior
• Neuro dz
• +/- systemic dz
• Metastaitic neoplasia, unless is primary/localized
• Loss of effective extensor mechanism (ie, patella/patella ligament)
• +/- collateral alig. Insufficiency → can repair at time of TKR, but poss. Increased copmlciations especially if MCL

Question 5

• What is the TPA of the implanted tibial component?

Answer 5

• 6

Question 6

• What does the optimal balance of the stifle depend on ?

Answer 6

• Alignment
• Joint laxity → tension in the soft tissues

Question 7

• What is the impact of removing too little bone or implanting too large components? Too much bone/implanting too small component?

Answer 7

• Too little/too big implant - increased joint tension = risk collateral rupture
• Too much/too small implan - uncontrolled out of plane joint motion + joint instability

Question 8

• What are 3 intraoperative complications?

Answer 8

• Collateral ligament damage
• Patella ligament damage
• Vascular compromise

Question 9

• What is the most common wear mechanism in TKR?

Answer 9

• Adhesive wear

Question 10

• What is the cause of adhesive wear, and what are 2 risk factors for this to occur?

Answer 10

• Excessive contact stress → delamination
• Risk of delamination → higher in implants with reduced contact area between femoral and tibia components or with thinner polyethylene inserts

Question 11

• What is the angle error above which joint instability is reported in the canine TKR?

Answer 11

• > 3 degrees of error in frontal plane alignment
• Altered loading → accelerated implant wear

Question 12

• What is the difference between 2 step revision and single stage?

Answer 12

• Single - direct exchange
• 2 step -> abx-loaded PMMA spacer for 6-12 weeks, then reised to new implant once infection is eliminated

Question 13

• What are 4 common post op complications following TKR in dogs?

Answer 13

• Aseptic loosening
• Reduced ROM
• Joint instability
• Infection