Personalized Revision Arthroplasty After Failed Medial Unicompartmental Knee Arthroplasty: A Contemporary Narrative Review

Medial unicompartmental knee arthroplasty (UKA) is a bone- and ligament-preserving alternative to total knee arthroplasty (TKA) for selected patients with isolated medial compartment osteoarthritis, but it carries a consistently higher revision rate. The assumption that a failed UKA converts easily to a primary-standard TKA has not survived registry scrutiny, and conversion is now best regarded as a formal revision procedure. This contemporary narrative review, which is not a systematic review, evaluates revision strategies after failed medial UKA. Sources were identified through targeted literature searches and reference-list screening, and the strength of evidence was graded by level of evidence. Three pathways are considered: revision within the medial compartment, including bearing and single-component exchange; retention of a well-fixed, well-positioned medial UKA with addition of a patellofemoral arthroplasty or a lateral UKA; and conversion to TKA. Evidence quality differs sharply between pathways. Conversion to TKA is supported by registry and comparative cohort data, and medial UKA-to-UKA revision mainly by evidence of its high failure rate. Compartmental addition rests on one small dedicated series, one small multicentre comparative study, one descriptive multicentre series, one expert consensus and indirect data from primary bicompartmental arthroplasty. A four-step framework is proposed (failure mechanism, compartmental mapping, bone and ligament assessment, patient and centre factors); it is evidence-informed but not validated.