TKA converted from UKA had higher revision risk vs primary TKA
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Published results showed a three-fold higher risk of revision when total knee arthroplasty was converted from medial unicompartmental knee arthroplasty compared with primary total knee arthroplasty.
Anders El- Galaly , MD, and colleagues compared 1,012 TKAs converted from medial unicompartmental knee arthroplasty (UKA) with 73,819 primary TKAs and 2,572 revision TKAs from the Danish Knee Arthroplasty Registry from 1997 to 2017. Researchers considered risk of revision as the primary outcome. Researchers also analyzed the influence of different implants, the indications for UKA conversion and surgical volume on the survival of TKA converted from UKA, and compared the indications for revision.
Researchers found 85% of the converted UKAs were mobile bearing. Compared with patients with primary TKA or revision TKA, at the time of conversion, patients who received UKA were younger and more were Charnley class A, according to results. Results showed TKAs converted from UKAs had comparable survival with that of revision TKAs and were significantly inferior to the survival of primary TKAs. Researchers noted differences in conversion implants, experience with revision surgery and the indications for the UKA-to-TKA conversion did not affect the survival of TKA converted from UKA. Frequent indications for revisions of TKA converted from UKA included instability and unexplained pain, according to results.
“UKA should be regarded as a definitive treatment in line with TKA because, if it fails, the survival of a TKA converted from a UKA is comparable with the survival of a TKA revision,” El-Galaly told Healio.com/Orthopedics. – by Casey Tingle
Disclosure: El-Galaly reports no relevant financial disclosures.
Perspective
Back to TopEmmanuel Thienpont, MD, MBA, PhD
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.”
University Hospital Saint Luc
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