Objective To introduce a classification of infection interfaces associated with existing implants which was used to guide the treatment algorithms for implants and infection.Methods From January 2006 to April 2016,197 patients were treated at Department of Bone Tumor Osteopathology,Zhengzhou Orthopaedics Hospital for early infection associated with an existing implant.They were 147 males and 50 females,aged from 12 to 63 years (average,47.3 years).After bacterial cultures and drug sensitive tests and other laboratory examinations,their infection interfaces were classified into 3 types.In type Ⅰ of 89 cases,the infection was confined to the soft tissue and spread to only part of the implant;in type Ⅱ of 75 cases,the infection spread to the internal implant but ended at the implant and bone surface,involving no intramedullary cavity;in type Ⅲ of 33 cases,the infection spread to the intramedullary cavity with defects at broken ends.In primary surgery,plating was performed in 126 cases,external fixation in 48 and intramedullary nailing in 23.Type I cases were treated by systemic intravenous infusion combined with local antibiotic therapy and/or limitedly extended debridement while the implants were reserved,type Ⅱ cases by extended debridement while the implants were reserved,and type Ⅲ cases by extended debridement and external fixation while the implants were removed.Antimicrobial therapy was conducted before and after surgery according to their pathogen examination results.Antibiotics were used after surgery according to their pathogen examination results.Their therapeutic outcomes were evaluated according to their systemic and local symptoms,signs,blood routine indexes,erythrocyte sedimentation rate and level of C reactive protein.Results All the patients were followed up for 2 to 5 years (mean,3.4 years).After antibiotic therapy,debridement and vacuum sealing drainage,the implants were reserved in 150 cases,of which 84 were type I and 66 type Ⅱ,and removed in 47 cases,of which 5 were type Ⅰ,9 type Ⅱ and 33 type Ⅲ.By the criteria described in Surgery for Pyogenic Infection of Bone and Joint,the therapeutic outcomes were rated as cured in 185 cases,as effective in 7 and ineffective in 5.Conclusions A classification of infection interfaces associated with existing implants is significant for scientific,reasonable,standardized and individualized treatment algorithms for implants and infection,avoiding not only incidence of osteomyelitis but also unnecessary removal of implants with effective control of inflammation.