Abstract
Achieving a primary outcome with revision UKR is possible but it depends on an understanding of the main failure modes and avoiding the obvious pitfalls. The most common failure mode in the long term is lateral compartment progression at 2.5% at 28 years. The most common failure overall is misdiagnosis of a painful radiolucency leading to unnecessary revision.
There are a number of potential pitfalls:
Do not revise for unexplained pain. 75% of patients will go on to fail because of continuing pain. A distinction must be made to differentiate between a physiological radiolucency (with a narrow lucency accompanied by a sclerotic margin which is normal) and a pathological radiolucency (with a poorly defined lucency without surrounding sclerotic margin which is indicative of loosening and/or infection)
Femoral loosening can present with subtle findings. Flexion/extension views are helpful to diagnose this problem.
Wear can be a problem with fixed bearing in the second decade and can present with subtle findings. Infection can present with contralateral compartment joint space narrowing.
The approach and exposure is usually straightforward and component removal is generally easy. Tibial resection is undertaken referenced from the normal lateral condyle removing 10mm of bone. Femoral preparation is generally straightforward but care must be taken to dial in correct rotation in the absence of the posterior medial condyle which was resected in the first operation. Generally a CR or PS primary implant is used with 2–4mm extra polyethylene thickness than is used in primary case.
Revision for infection and stress fracture led to difficult revisions where revision components are usually required.
The results for Revision UKR approach those of a primary procedure in all cases except revision for unexplained pain, infection and a stress fracture.
