Review Question - QID 214426

The most common cause of late failure and revision of unicompartmental knee arthroplasty (UKA) is the progression of osteoarthritis.

Late failure (>10 years) of UKA is most commonly caused by progression of arthritis. Other causes of failure include aseptic loosening, instability, infection, unexplained pain, and polyethylene wear. Interestingly, while TKA saw improved survival with improved polyethylene from the 1990s to the 2000s, UKA did not see a large change in survivorship suggesting that progression of osteoarthritis may be an unmodifiable mode of failure of these implants.

Jennings et al. review medial UKA. They state early medial UKA failures (<5 years) were from aseptic loosening (25%) with the progression of osteoarthritis second at 20%. However midterm and late failures were more commonly due to the progression of osteoarthritis (38 to 40%) with aseptic loosening (29%) and polyethylene wear (10%) as the next most common modes of failure.

Borus et al. reviewed UKA with regard to the evolution of the procedure. They found that at 10 years, one registry study found the progression of arthritis (51%) to be the most common cause of failure. They also cite a study that showed that mobile-bearing UKA tended to fail more from the progression of arthritis while fixed-bearing UKA failed due to tibial component failure.

Incorrect Answers:
Answer 1: Aseptic loosening is a major cause of failed UKA however it's more common in the early period (<5 years).
Answer 3: Unexplained pain can occur and cause the failure of UKA, but it does not occur as often as the progression of arthritis.
Answer 4: Instability can occur and cause the failure of UKA, but it does not occur as often as the progression of arthritis.
Answer 5: Infection can occur and cause failure of UKA, but it does not occur as often as the progression of arthritis.