Ch 62 - Total Knee Replacement

Question 1

What is the below implant?
What are its components made of?

Answer 1

BioMedtrix Canine Total Knee Replacement
- A = Articulated construct
- B = Inverted tibial component. Made of UHMW polyethylene and is undercut to allow cemented fixation
- C = Femoral component, positioned to show non-articulating surface coated with beads for press-fit, cementless fixation. Made of cobalt-chromium alloy

Question 2

What is the recommendation for patients presenting for a total knee replacement with current TPLO implants or other stifle implants?

Answer 2

• Remove implants atleast 6 weeks prior to TKR
• Culture of synovium and peri-implant tissue

Question 3

List two absolute contraindications for TKR

Answer 3

• Infection
• Loss of effective extensor mechanism

Question 4

What are the recommendations regarding implantation of the tibial component?

Answer 4

• 90 degrees to the mechanical axis of the tibia in the frontal plane
• Sagittal slope at 6 degrees

Question 5

What factors affect optimal balance of the implants?

Answer 5

• Alignment
• Joint laxity (tension within the periarticular soft tissues)

Question 6

List potential intra-operative complications

Answer 6

• Inadvertent damage to collateral ligaments of patellar ligament
• Femoral or tibial fracture
• Haemorrhage (stifle should be flexed and placed into cranial drawer during the tibial osteotomy while protecting the vascular structures within the popliteal fossa)

Question 7

List potential post-op complications?

Answer 7

• Implant wear
• Aseptic loosening
• Chronic instability
• Limited range of motion (Arthrofibrosis)
• Infection

Question 8

What is the most common organism cultures in infected TKR?
What are the treatment options?

Answer 8

Multidrug Resistant Staph

Treatment Options:
- Chronic medical managment
- Surgical debridement with retention of implants
- Revision (remove implants, ABx impregnated spacer for 6-12wk, new implant)
- Arthrodesis
- Amputation