Conversion Unicondylar Knee Arthroplasty in the Indian Patient: What Can You Expect?

Our aim was to compare the clinical outcomes of conversion unicompartmental knee arthroplasty (UKA) with (a) primary total knee arthroplasty (TKA) and (b) revision TKA.

We retrospectively identified 17 patients undergoing conversion of UKA to TKA by a single surgeon with a minimum 1 year follow-up. These patients were matched 1:1 to patients undergoing primary TKA and revision TKA based on age, sex, BMI and time to final follow-up forming three groups: conversion UKA group (C-UKA), primary TKA group (P-TKA) and revision TKA group (R-TKA). Clinical outcomes were compared using New Knee Society Score (NKSS) and Forgotten Joint Score (FJS). The level of significance was set at 0.05.

The average time to surgery in the C-UKA group was 7.2 years (range 2.5-17.2), with 82.5% being less than 10 years from index UKA. The mean follow-up was 3.7 years in the C-UKA group. All patients required more than a primary component on the tibial side. Flexion (p = 0.03), symptom (p < 0.001) and function (p < 0.001) subcomponent as well as total NKSS (p = 0.001) were significantly lower in the C-UKA group as compared to the P-TKA group. The flexion (p = 0.67), FJS (p = 0.71) as well as the NKSS and its subcomponents were comparable (p > 0.05) between the C-UKA and R-TKA groups.

When performing conversion of a medial UKA in the Indian population, a revision component is required in all patients on the tibial side. The clinical outcomes of conversion UKA were poorer than a primary TKA and more comparable to a revision TKA. Surgeons should keep this in consideration when performing a medial UKA, especially in cases with extended indications.