Anders El-Galaly, MD, and colleagues report Danish arthroplasty registry results from 1997 to 2019 on about 100,000 implants. Ten percent of the medial UKAs were converted to TKA within that period. Of those, 85% were mobile-bearing designs. The main reasons for revision were aseptic loosening, instability, progression of arthritis and unexplained pain. Survival of this group was comparable to revision TKA and inferior to primary TKA (hazard ratio 3).
This paper shows that getting it right the first time remains crucial. Ten percent of UKAs revised to TKAs needed a second revision. Furthermore, aseptic loosening, instability and unexplained pain remained the main reason for second revision.
A clear definition of aseptic loosening and instability should be developed, leading to a consensus about the indications for revision. Revision for unexplained pain should only be done after a discussion with pain specialists. These three major indications for re-revision remain at the discretion of the treating surgeon.
The authors stated in their conclusion that “careful consideration is necessary before using medial UKA as treatment for knee osteoarthritis,” but 85% were mobile bearings. Radiolucent lines and instability are less frequent in fixed-bearing UKA. They could have stated “before using a mobile-bearing UKA.”
Emmanuel Thienpont, MD, MBA, PhD
Head of knee surgery
University Hospital Saint Luc
Disclosures: Thienpont reports he is a consultant for Convatec, KCI, Lima, Medacta and Zimmer Biomet and receives royalties from Zimmer Biomet.