Converting a Uni to a Total Knee Arthroplasty

    With more unicompartmental knee arthroplasty (UKA) procedures being performed today, joint replacement surgeons will need to be prepared for the increase in revision procedures required in the coming decades.

    That’s not a knock on UKA: Remember, the increase in total knee arthroplasty (TKA) procedures is also predicted to result in a corresponding need for more TKA revisions.

    UKA is a good procedure for anteriomedial osteoarthritis (OA), noted Duke University’s Michael P. Bolognesi, MD, at ICJR’s Revision Hip & Knee Course, with mid- and long-term results comparable to those of primary TKA.

    No matter how good it is, though, it’s not perfect: Implants fail, complications arise, technical issues occur – just as with TKA.

    UKAs fail for some of the same reasons that TKAs fail – such as infection, wear, instability, and component loosening – as well as progression of OA to other compartments, Dr. Bolognesi said.

    And the principles for revising a UKA to a TKA are similar to those of revising a primary TKA – such as not revising the UKA unless a definitive reason for the failure is found.

    In most cases, a failed UKA will be revised to a TKA. Dr. Bolognesi warned against revising a UKA to another UKA unless the components are stable and in good position. He gave 2 examples:

    • Exchanging undersized bearings
    • Addressing a dislocated bearing that dislodged by retained posterior osteophytes

    When the decision is made to revise a UKA to a TKA, the surgeon should be prepared to address:

    • Bone defects
    • The joint line
    • Component sizing and rotation

    In most cases, Dr. Bolognesi said, the UKA-to-TKA conversion can be accomplished with implants used for a primary TKA, as studies have shown UKA revisions with primary TKA implants to have survivorship similar to that of primary TKAs.

    Augments or screws and cement are often needed for focal defects, he said, but most studies have shown that constrained constructs are not necessary.

    Click on the image above to watch Dr. Bolognesi’s presentation, which includes pearls for distal femoral resection, tibial preparation, and tibial resection.