Does Unicondylar Knee Arthroplasty Failure Mode Impact Conversion Total Knee Arthroplasty Outcomes?

Area of Science:

• Orthopedic Surgery
• Arthroplasty Research
• Biomedical Engineering

Background:

• Conversion of unicondylar knee arthroplasty (UKA) to total knee arthroplasty (TKA) involves higher costs and complication rates than primary TKA.
• The impact of specific aseptic failure modes of UKA on the success of subsequent TKA remains unclear.

Purpose of the Study:

• To evaluate if the aseptic failure mode of unicondylar knee arthroplasty influences the survivorship of subsequent total knee arthroplasty.
• To compare the outcomes of UKA conversion to TKA with primary TKA and revision TKA.

Main Methods:

• A prospectively maintained database identified 439 UKA to TKA conversions between 2000 and 2023.
• Aseptic failures were analyzed (n=413), comparing survivorship based on failure mode (osteoarthritis progression, component loosening, wear, fracture).
• Outcomes were compared to 15,026 primary TKAs and 1,432 revision TKAs, with a mean follow-up of 5.7 years.

Main Results:

• No significant difference in TKA survivorship was found based on the aseptic failure mode of the preceding UKA (P=0.80).
• Common reasons for conversion included osteoarthritis progression (31%), tibial component loosening/subsidence (27%), and polyethylene wear/osteolysis (22%).
• Aseptic conversion TKA demonstrated comparable 10-year survivorship to primary TKA (95.6% vs. 95.8%, P=0.72) and superior survivorship to revision TKA (84.2%, P<0.001).

Conclusions:

• Conversion of UKA to TKA yields successful outcomes irrespective of the aseptic failure etiology.
• The survivorship of UKA conversion to TKA is comparable to primary TKA and superior to revision TKA, supporting its use in revision settings.