How Do UKA and TKA Compare at 10 Years after Surgery?

    In a study from OrthoCarolina, the reoperation rate was higher for unicompartmental knee arthroplasty than for total knee arthroplasty, but patients in the 2 groups had similar outcome scores.

    Unicompartmental knee arthroplasty (UKA) is performed less commonly in the US than in Europe, with many American surgeons opting for a total knee arthroplasty (TKA) even when only 1 compartment of the knee is affected by osteoarthritis. The thinking is that since outcomes are typically better with TKA, and since the UKA will probably need to be revised to a TKA at some point, why not just start with the TKA?

    But is that thinking right? Maybe for some patients, but a study from OrthoCarolina has shown that in patients with comparable preoperative knee function and pathology, outcomes of UKA and TKA are similar 10 years after surgery. The main difference is risk of reoperation: It was 2.3 times higher in UKA patients than in TKA patients in this study.

    These findings were reported at the 2018 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).

    To prospectively evaluate the clinical outcomes of UKA versus TKA, the researchers compared 103 UKA patients and 72 TKA patients from OrthoCarolina who completed WOMAC and KOOS questionnaires at 2 and 10 years following surgery. They also recorded reoperation rates and the reason for failure.

    Interestingly, the decision to perform a UKA or a TKA in this patient cohort was made intraoperatively based on the observed pathology from osteoarthritis. “The study results validate the concept of intraoperative procedure selection to provide the optimal procedure,” said lead study author John L. Masonis, MD.

    Dr. Masonis was trained in UKA during his fellowship, and he has performed UKAs over the past 18 years. About 5% of his knee replacement procedures are UKAs. The benefits of UKA compared with TKA, he said, are:

    • Easier recovery
    • Lower infection risk
    • More normal knee kinematics due to preservation of the cruciate ligaments

    But “this needs to be weighed against a revision rate that is 2.3 times higher at 10 years,” he said.

    In the study presented at the AAOS meeting, Dr. Masonis reported that 17 of 103 UKA patients (16%) and 5 of 72 TKA patients (6.9%) had undergone a reoperation in the 10 years since the initial procedure (P=0.03). Failure modes were different for the 2 groups:

    • For UKA, aseptic loosening (53%; 9/17), progression of adjacent compartment osteoarthritis (23%; 4/17), pain with well-fixed components (18%; 3/17), and polyethylene wear (6%; 1/17)
    • For TKA, arthrofibrosis (60%; 3/5), infection (20%; 1/5), and aseptic loosening (20%; 1/5)

    Patients reported the following mean function scores at the 10-year follow-up:

    • WOMAC Stiffness: 100 for UKA and 88 for TKA (P=0.39)
    • WOMAC Function: 97.1 for both groups (P=0.78)
    • WOMAC Total: 97.9 for UKA and 95.8 for TKA (P=0.61)
    • KOOS Symptoms: 92.9 for UKA and 89.2 for TKA (P=0.02)
    • KOOS Pain: 97.2 for both groups (P=0.56)
    • KOOS Activities of Daily Living: 97.1 for both groups (P=0.78)
    • KOOS Sport and Leisure: 75 for UKA and 70 for TKA (P=0.97)
    • KOOS Quality of Life: (87.5 for UKA and 81.2 for TKA (P=0.43)

    “The most surprising result of this study was the near equal patient function scores between UKA and TKA,” Dr. Masonis said. “The UKA had a slight advantage, but not a major one. This could be a function of the tool/scoring system used to assess” function.

    The main takeaway from the study, Dr. Masonis said, is that it provides “10-year data that surgeons can discuss with patients when deciding on UKA versus TKA.”


    Masonis JL, Hart GP, Odum SM. Ten-Year Outcomes of Unicompartmental Knee Arthroplasty versus Total Knee Arthroplasty Using an Intraoperative Procedure Selection in Patients with Similar Preoperative Function and Arthritis. (Paper 493). Presented at the 2018 Annual Meeting of the American Academy of Orthopaedic Surgeons, March 6-10, 2018, New Orleans, Louisiana.


    The study authors have no disclosures relevant to this presentation.