OrthoNet

TKA - Approach to Patellar Failure

Factors Associated with Patellar Failure
1. Metal Backing - #1 cause 5. Increased Postop Flexion
2. Patellar Instability 6. Increased Patellar Thickness - increases jt reaction forces
3. Elevation of Joint Line
4. Asymmetric Patellar Cut

- the first thing to decide is whether the whole thing needs to be revised - ie. what was the cause of patellar failure? If you do not address this, the patella will inevitably fail again. Be prepared to revise it all.

Management

- revising a patella can be very difficult - there may not be much bone left to secure another prosthesis
- if sufficient bone stock is left - great, revise the component
- if insufficient bone stock is left - consider patellaplasty or patellectomy; resist the temptation to resurface an inadequate patella
- if revising a metal backed patella - you must do a thorough debridement of all the metallosis. Also, inspect the femoral surface for wear from the metal backing on the patella.