Lateral UKA Is Associated With Mixed 90-Day and 5-Year Outcomes Relative to Medial UKA and TKA

Unicompartmental knee arthroplasty (UKA) is an option for unicompartmental osteoarthritis. With medial or multicompartment joint wear being the most common clinical scenarios, lateral UKA (L-UKA) is less commonly considered than other knee joint arthroplasty procedures. As such, the postoperative outcomes of L-UKA relative to medial UKA (M-UKA) and total knee arthroplasty (TKA) remain poorly characterized at a national level in the United States.

Patients undergoing L-UKA were identified from the PearlDiver M170Ortho Database and separately matched 1:4 with M-UKA and TKA patients by age, sex, and Elixhauser Comorbidity Index. Multivariable logistic regression compared 90-day adverse events, emergency department visits, readmissions, and 5-year implant-related issues.

First, 343 L-UKAs were assessed relative to 1,295 M-UKAs. L-UKA demonstrated higher odds of 90-day severe adverse events (odds ratio [OR], 1.83; P = 0.037), infection (OR, 1.41; P = 0.022), wound dehiscence (OR, 3.60; P = 0.008), readmission (OR, 1.67; P = 0.047), and 5-year prosthetic joint infection (OR, 2.57; P = 0.001). Second, 425 L-UKAs were assessed relative to 1,700 TKAs. L-UKA demonstrated higher odds of 90-day wound dehiscence (OR, 2.13; P = 0.025), 5-year prosthetic joint infection (OR, 1.64; P = 0.028), and revision (OR, 2.00; P = 0.007), but lower odds of 5-year stiffness (OR, 0.45; P < 0.001).

In the first study of L-UKA using national-level US data, L-UKA demonstrated mixed outcomes compared with both M-UKA and TKA. While L-UKA demonstrated lower stiffness rates than TKA, the elevated risk of 90-day postoperative complications and inferior 5-year revision-free survival suggest the need for careful consideration of L-UKA and future prospective analysis to further elucidate whether these associations can be generalized across surgeons with differing case volumes.