LOCO Total Knee replacement Flashcards
Which surfaces are replaced in TKR
Femoral, tibial and patellar articular surfaces
What are the most common indications for TKR
Debilitating osteoarthritis
Inflammatory arthritis
Trauma
What are contraindications for TKR
- Neuropathic arthropathy
- Infection
What are the components of TKR and what are they made of
Tibial component: High density polythene spacer
Femoral component: metallic component contoured similarly to the condyles and trochlea
Patellar component: high-density polythene, it may be metal backed
Can be cemented (PMMA) or uncemented
What are the changeable factors in TKR
- degree of constraint
- Polythene spacer fixation
- PCL retention or removal
How might degree of constraint change in TKR and why
Degree of constraint is proportional to the amount of support the patients soft tissues can provied
Unconstrained prosthesis: Most widely used, most unstable but patients soft tissues maintain the joint
Semi-constrained:
More stable but decreased range of motion, consists of closely conforming tibial and femoral parts
Constrained: hinged mechanism, it is the most stable but most limited range of motion, there is greater mechanical stress fatigue and loosening. It is used in revision arthroplasty, elderly patients with unstable ligaments and in combination with tumour resection
What is a spacer and why might you use a fixed one over a mobile one
A spacer sits between the tibial and fibial components to prevent them from rubbing (acts like a synthetic meniscus)
Fixed bearing spacers are fixed within the metal tibial tray. More stable, used for less active patients
Mobile bearing: a mobile polythene insert glides over the surface of the metallic tibial component, allows more movement but is less stable
What are the options for PCL retention/removal in TKR
The PCL can be retained (normally the case in unconstrained prostheses), removed or removed and substituted for. Some studies suggest that substitution should be done if the PCL can’t be retained in order to stabilise the knee joint
What is the 15 year endurance of TKR
95%
What are the different X-ray views used to follow up TKRs
AP, Lateral and Skyline merchant
What nerve is commonly injured in TKR
Common peroneal
