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

BACKGROUND: 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. METHODS: 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. RESULTS: 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). DISCUSSION: 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.