Combined procedures with unicompartmental knee arthroplasty: High risk of stiffness but promising concept in selected indications.

INTRODUCTION: Unicompartmental knee arthroplasty (UKA) has traditionally been contraindicated in the presence of an ACL deficient knee, bi-compartmental disease, or significant coronal deformity due to concerns regarding increased risk of persisted pain, knee instability, tibial loosening, or progression of osteoarthritis. The aim of this study was to evaluate the outcomes of patients undergoing UKA with an associated surgical procedure in these specific indications. METHOD: This was a retrospective cohort study of patients undergoing UKA between December 2015 and October 2020. Patients were categorized into groups based on associated procedures: UKA + ACL, UKA + HTO, and bicompartmental arthroplasty. Outcomes were assessed using the Knee Society Score (KSS) knee and function scores and the Forgotten Joint Score. Radiological and complication analysis was performed at the last clinical follow-up. RESULTS: Thirty-two patients (13 men and 19 women) were included. The mean age was 56.2 years ± 11.1 (range, 33-84) with a mean follow-up of 26.3 months ± 15 (7.3-61.1). There was a significant improvement between the pre-and postoperative KSS Knee (+34.3 ± 16.5 [12-69]), Function (+34.3 ± 18.6 [0-75]), and Total scores (+68.5 ± 29.4 [24-129]) (p = 0.001). Seven patients (21.8%) required an arthroscopic arthrolysis for persistent stiffness. Two patients (UKA + PFA and UKA + ACL) underwent revision to TKA. Patient satisfaction was 90%, and mean flexion at last follow-up was 122° ± 6 (120-140). The implant survival rate was 94%. DISCUSSION: This study found performing UKA with an additional procedure to address relative contraindications to the arthroplasty in physically active patients with monocompartmental knee arthritis is an efficient strategy with good results at short-term follow-up. It should be reserved for patients where TKA is likely to have unsatisfactory results, and the patient has been fully counseled regarding the management options. Even if there is a high rate of complications with stiffness requiring a re-intervention, the final results are very satisfying with no impact of the reintervention on the clinical result in the short term.