Clinical Outcomes and Survivorship of Lateral Unicompartmental Knee Arthroplasty: A Large Single Surgeon Cohort.

Background: Lateral unicompartmental knee arthroplasty (UKA) is an effective treatment for isolated lateral compartment osteoarthritis. However, due to the rarity of the procedure, long-term outcomes and survivorship are poorly understood. We report the clinical and radiographic outcomes after lateral UKA.

Methods: We retrospectively reviewed a consecutive series of patients who underwent lateral UKA by a single fellowship-trained arthroplasty surgeon from 2001 to 2021 with a minimum 2 year follow up. There were 161 knees in 153 patients (average age 69 years) that met inclusion criteria, with a mean follow up of 10.0 years (range 0.05 to 22.2). All patients underwent the procedure via a minimally invasive lateral parapatellar approach with a fixed-bearing implant. Patient demographics, complications, radiographic findings, patient-reported outcomes, and the need for revision surgery were evaluated. Survivorship was defined with the end point as revision of components.

Results: There were 8 patients (5.0%) who underwent conversion to total knee arthroplasty for lateral UKA implant failure or progression of arthritis. There were 3 patients (1.9%) who underwent ipsilateral medial UKA due to medial compartment arthritis progression with preserved mechanical alignment and patellofemoral joint. There were 8 additional procedures that did not require implant changes, including 5 irrigation and debridements for acute periprosthetic joint infection (3.1%), 2 wound closures for dehiscence (1.3%), and one loose body removal (0.6%).

Conclusions: Lateral UKA showed a survivorship rate of 98.0% at 5 years, 96.0% at 10 years, and 94.5% at 15 years. When including patients who underwent additional surgery for the progression of arthritis, survivorship was 97.4% at 5 years, 95.4% at 10 years, and 91.3% at 15 years. Lateral UKA should be seen as a durable treatment option for isolated lateral compartment osteoarthritis.