Ch 62 Total knee replacement

Question 1

indications for TKR:

Answer 1

• end stage OA
• osteochondrosis,
• intra-articular fractures
• collateral ligament injury/luxationn
• bone deformities.

Question 2

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

Answer 2

BioMedtrix Canine Total Knee Replacement
- semiconstrained implant design
- 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 3

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

Answer 3

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

most of the patients that are referred for total knee replacement present with a history of failed surgical managemen

Question 4

List two absolute contraindications for TKR

Answer 4

1. Infection
2. Loss of effective extensor mechanism

Question 5

important consdierations prior to TKR (6)

Answer 5

considerations:
- rule out concurrent neurologic disease
- perform arthrocentesis if had previous sx , - resolve pyoderma, urinary tract infection, otitis externa, and periodontal disease prior to surgery
- effects of immunosuppressive/systemic disease
- stable, pain-free contralateral limb on which to bear weight during recovery from total knee replacement
- correction of the alignment problem (MPL or valgus/varsus) is advised prior

distal femoral varus because acute correction results in an immediate increase in loading on the medial collateral ligament, likely increasing the risk of ligament disruption

Question 6

indications for cementless over pressfit (3)

Answer 6

cement preferred only for dogs with:
- suboptimal bone quality associated with advanced age,
- chronic disuse osteopenia
- concurrent disease (neoplasia)

Question 7

common causes for need of revision (3)

how to revise? custome implants

Long-term data on revision not yet been published.

Answer 7

1. infection
2. collateral ligament disruption
3. aseptic loosening

• for Coltaeral ligament: fixed-axis hinge implant, constrained condylar implant rotating hinge
• aseptic loosening: cemented, long-stemmed revision implant

Question 8

isolated patellofemoral osteoarthritis

Answer 8

• Replacement of the patella has not been an option
• PGR, Kyon is now an option.

Question 9

What are the recommendations regarding implantation of the tibial component?

Answer 9

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

mirror the current recommendations for managing CCLR by TPLO.

Question 10

What factors effect optimal balance of the implants (2)?

Answer 10

• Alignment (rotational, sagital and frontal)
• Joint laxity (tension within the periarticular soft tissues)

poor alignment increase risk of late implant failure

Question 11

semiconstrained implant design

how affects joint stability?

Answer 11

• articular geometries of the femoral and tibial implants are closely matched to provide resistance against excessive cranial-caudal translation and internal-external rotation.
• Undertensioning the collateral ligaments, (removal of too much bone or too small ikmplats) permits uncontrolled joint instability.
• removal of too little bone or too large implant increases joint tension and increases the risk of collateral ligament rupture

Question 12

ensuring complete removal of the diseased cartilage from the articular surfaces of the femur and tibia

Question 13

technical goal of TKR

Answer 13

restoration of normal stifle joint alignment and balance

Question 14

List potential intra-operative complications (4)

Answer 14

• Inadvertent damage to collateral ligaments
• damage to patellar ligament
• Femoral or tibial fracture
• Haemorrhage (stifle should be flexed and placed into cranial drawer during the tibial osteotomy)

Question 15

List potential post-op complications? (5)

Answer 15

Implant wear
- physical damage to the bearing surfaces of the implant degrades the “low-friction” performance of the articulation.
- the damage leads to the release of particulate and, for metals, ionic wear products)
- adhesive wear and subsurface failure (delamination) occurs in humans and in experimental dog
- to reduce: ensure approriate balance and alignment, design that distribute femorotibial loading over an expanded contact area

Aseptic loosening
- wear debris incite an inflammatory response that ultimately leads to periprosthetic bone resorption
- most common cause in human TKR

Chronic instability

Limited ROM (Arthrofibrosis)
- Rehabilitation therapy should be offered for any dog

Infection
- RADS: separation of the cement-bone interface, osteolysis, periosteal reaction
- multidrug-resistant Staphylococcus spp
- biofilm that reduces the chances of positive identification through standard culture techniques

Question 16

What are the treatment options of TKR infection?

multidrug-resistant Staphylococcus spp

Answer 16

• Chronic medical managment with ab’s
• Surgical debridement with retention of implants
• Revision (remove implants, ABx impregnated spacer for 6-12wk, new implant) > introduction of custom revision implants
• Arthrodesis
• Amputation

organism subsequently re-emerged several months after the revision surgery

vancomycin-loaded spacers

Question 17

3D-printed, patient-specific cutting guides improve femoral and tibial cut alignment in canine total knee replacement
Fracka 2023

Answer 17

cadaveric study
determine whether patient-specific guides (PSGs) improve the accuracy of tibial and femoral cut alignment in canine total knee replacement (TKR)

3D-printed PSGs improved tibial cut alignment in the frontal plane but not the sagittal plane.
PSGs also improved the alignment of the cranial and distal femoral ostectomies but did not impact varus-valgus alignment.

Clinical trials are now needed

end-stage disease and varying
degrees of bone deformity and joint collapse that can
complicate the use of generic cutting guides

Question 18

Custom-built constrained uniaxial and rotating hinge total
knee replacement in cats: Clinical application, design
principles, surgical technique, and clinical outcome
Fitzpatrick 2020

Answer 18

Retrospective case series.
Animals: Nine cats, 8 with luxation
follow-up time was increased to 29 months (range, 22-47) when results of
functional questionnaires with owner were included. Median radiographic
follow-up was 12 months
One cat had a catastrophic outcome.
Three cats had good outcomes, and five cats had excellent outcomes.

four of eight stifles before proceeding
with TKR because of failure of primary
stabilization

only hinged implants can provide stability in
cases of dual collateral ligament rupture

Major complications: 2
Cat 1 rupture of the patellar ligament
Cat 2 underwent revision surgery 18 days after implantation because of restricted ROM and poor performance

a thick coupling UHMWPE bushing with large contact surface area, immediate stability, bone in-growth
over time,

range of motion of G3 implants was limited by the
implant mechanics, with a maximum extension angle of
144 , which is still similar to recently published stifle
standing angles in cats (approximately 143 ).