From classification to management: how classification systems influence treatment of periprosthetic fractures following total knee arthroplasty

Periprosthetic fractures (PPFs) following total knee arthroplasty (TKA) are an increasing source of morbidity. The Unified Classification System (UCS) provides a comprehensive framework encompassing the distal femur, tibia, patella, and interprosthetic region, while commonly used site-specific classification systems refine treatment decisions according to fracture location. This review evaluates the complementary roles of the UCS and site-specific classifications and examines their influence on clinical management. A structured narrative review was performed using PubMed and Google Scholar from inception to March 2025. Studies evaluating classification systems and management strategies for PPFs following TKA were identified using predefined MeSH and free-text search terms. Evidence quality was appraised using the Oxford Centre for Evidence-Based Medicine (OCEBM) hierarchy and considered during interpretation. The UCS provides a unified descriptive framework applicable across all anatomical sites, whereas commonly used site-specific classification systems contribute additional information regarding implant stability, fracture location, bone stock, and extensor mechanism integrity to guide operative decision-making. Although treatment recommendations generally align for stable implants, differences between classification systems may influence management when implant loosening or complex fracture patterns are present. Current evidence also demonstrates higher reported inter-observer reliability for the UCS than for several individual site-specific classification systems. However, most available studies are retrospective, and no prospective studies have directly compared outcomes between classification-guided treatment pathways. The UCS provides the overarching framework for classifying periprosthetic fractures following TKA, while commonly used site-specific classification systems complement clinical decision-making by refining treatment according to fracture location and implant characteristics. The influence of classification choice on clinical outcomes remains inferential because prospective comparative validation is lacking. Future multicentre studies are needed to evaluate integrated UCS-guided treatment strategies.