TKA

Question 1

Most significant factor influencing post-operative flexion

Answer 1

Pre-uperative range of flexion

Question 2

Rationale to introduce mobile bearing knee replacements

Answer 2

To prevent excessive stresses at the bone-implantat interface

Question 3

Complications

Answer 3

Infection

DVT and PE

wound healing complications

Scar pain and lateral skin numbness
Infra-patellar branch of the saphenous nerve or its terminal branches

Ligament and tendon injuries

Longer-term quadriceps and hamstring weakness

Extensor mechanism disruption

Common peroneal nerve injury
Eg traction injury when correcting valgus deformity >10°

Vascular injury

Intra-operative fracture
! BMD (particularly the femoral condyles during box cuts of posteriorly stabilised implants)

Peripeosthetic fractures
F>M, older>younger

Amputation

Bleeding /transfusion reaction
Median blood loss : 1000ml

Tourniquet related problems
eg nerve injury (compression and ischaemia)

Clicking and grinding noises

Patellar clunk syndrome
Painful catching, grinding or jumping of the patella when the knee moves from a flexed to an extended position
Mostly in posteriorly stabilised knees, caused by a fibrous nodule that forms on the undersurface of the quadriceps tendon above the superior pole of patella

Stiffness / arthrofibrosis

Knee prosthesis instability and dislocation
Greater rates in those with severe knee deformities

Anaesthesia

Risk from nerve blockade

Medical complications
Elective TKR should be performed at least 1 year after an acute MI or cardiac stenting

Death
30-day mortality rate 1 in 270
90-day mortality rate 1 in 126

Question 4

Standard radiographs for revision TKA

Answer 4

AP
lateral
Skyline
Long-leg

Question 5

In revision cases, examine x-rays for

Answer 5

Overall alignment
Proximal tibial and distal femoral angles
Flexion or extension of implants
The posterior condylar offset ratio
Evidence of anterior overstuffing

Question 6

AB in spacer

Answer 6

Vancomycin and gentamycin

Question 7

Classification system for bone loss

Answer 7

AORI
Anderson Orthopaedic Research Institute classification

Femur and tibia classified separately
Might assist in implant selection

Type 1
Metaphyseal bone intact
No effect on stability of component
May be addressed with simple cancellous bone grafting and primary components

Type 2
Metaphyseal bone damaged
Loss of cancellous bone in the metaphyseal segment in one femoral condyle or tibial plateau (type 2A) or both condyles or plateau (type 2B)
May require cement augmentation, metal augments or bone grafting to restore the joint line

Type 3
Metaphyseal bone deficient
Bone loss in major portion of condyle or plateau, occasionally leading to ligamental detachment
May require structural bone grafting, metapyseal sleeves or trabecular metal cones

Question 8

Goal for kinematic alignment

Answer 8

Maintain the native joint line

Question 9

Technical goal

Answer 9

Place the TKA in neutral mechanical alignment