Unicompartmental Knee Osteoarthritis: Unicompartmental Knee Arthroplasty

Abstract

The best indication for UKA is painful osteoarthritis in an isolated tibiofemoral compartment (medial or lateral). An age younger than 60 years, a weight of 180 lb. (82 kg) or more, performing heavy work, having chondrocalcinosis, and having an exposed bone in the patellofemoral (PF) joint are not contraindications for unicompartmental knee arthroplasty (UKA). Severe impairment of the lateral facet of the PF joint with bone loss and grooving is a contraindication for UKA. Medial UKA should only be performed in cases of severe osteoarthritis (OA) as shown in preoperative X-rays, with medial bone-on-bone contact and a medial/lateral ratio of 95% for UKAs performed for medial OA or osteonecrosis and for lateral UKA, especially when fixed-bearing implants are used. When all implant-related reoperations are considered failures, the 10-year survival rate is 94% and the 15-year survival rate is 91%. Aseptic loosening is the principal failure mechanism in the first few years and in mobile-bearing implants, whereas OA progression causes most failures in later years and in fixed-bearing implants. The comprehensive complication rate and the comprehensive reoperation rate are comparable between mobile bearings and fixed bearings. The survival likelihood of the all-polyethylene UKA implant is similar to that of metal-backed modular designs for UKA. Notable cost savings of approximately 50% can be achieved with an outpatient UKA surgery protocol. Outpatient surgery for UKA is efficacious and safe, with satisfactory clinical results.