What to Do If a Medial Unicompartmental Knee Arthroplasty Fails

The rate of revision surgery for unicompartmental knee arthroplasty (UKA) varies depending on the publication, but survival increases with the expertise of the centres and practitioners. Unexplained pain can be an early manifestation of loosening, and dislocation of the polyethylene insert is specific to implants with a mobile insert. UKA failure due to allergy should be considered in a consultation, with an allergy screening questionnaire advisable. Measures to be taken on wear progression should include valgus position, conserved joint amplitude, and efficient ligament system. Patellofemoral arthroplasty should be considered in light of UKA deterioration and Iwano radiological stage 3 or 4. Revision surgery with TKR is the most common approach. Implant choice should consider present or potential loss of bone substance. Medial UKA implants should be kept as long as possible during revision surgery. Lewis et al. found that use of a stem increased survival at 10 years, and cemented implants are better than cementless implants. The operator should assess the difference between the section and the healthy area of bone under the medial tibial implant before selecting a revision technique. Perioperatively, tibial resection can be used as an autologous bone graft augment if bone quality is satisfactory, and the difference between the scheduled height of the lateral cut and the medial cut in the healthy area must be assessed. Preparation of the tibial baseplate is essential for successful UKA and sepsis management, which is based on clinical findings and a warm swollen knee. In cases of acute or chronic infection, imaging has little utility and antibiotic therapy should be targeted. Risk factors increase the probability of infection, and dislocation of the polyethylene implant should be considered based on sudden deterioration of the clinical result. UKA inserts can be dislocated due to perioperative technical issues, CAM effect, MCL insufficiency, asymmetry of joint spaces, malposition of an implant, or an insert increased by 1 mm. UKA is a surgical procedure with excellent functional results, but failures are increasing due to loosening of the tibial implant. Total arthroplasty is the most widely used solution, with implants sealed with a stem and augmenting whenever necessary.