[Low UKA implantation volume, comorbidities, male sex, and implantation of constrained TKA are risk factors for septic revision after knee arthroplasty implantation : A register-based study from the German Arthroplasty Register]. / Geringes UKA-Implantationsvolumen, Komorbiditäten, männliches Geschlecht und die Implantation einer gekoppelten TKA sind Risikofaktoren für septische Revisionen nach Knieprothesenimplantation : Eine registerbasierte Studie aus dem Deutschen Endoprothesenregister (EPRD).

ABSTRACT

AIM: Periprosthetic joint infection (PJI) is one of the main causes of revision surgeries after total knee arthroplasty (TKA) and unicondylar knee replacement. Patient- and hospital-related risk factors must be evaluated to prevent PJI. This study identifies influencing factors and differences in infection rates between various types of implant. METHODS: The basis for the data is the German Arthroplasty Register (EPRD). Septic revisions were calculated with the aid of Kaplan-Meier estimates, with septic revision surgery defined as the primary endpoint. Patients with constrained and unconstrained TKA or UKA were analysed using the Holm multiple log-rank test and the Cox proportional hazard model. The 300,998 cases of knee arthroplasty analysed included 254,144 (84.4%) unconstrained TKA, 9993 (3.3%) constrained TKA and 36,861 (12.3%) UKA, with a maximum follow-up of 7 years. RESULTS: After 1 year, the PJI rate was 0.5% for UKA and 2.8% for TKA, whereas after 7 years it was 4.5% for UKA and 0.9% for TKA (p < 0.0001). In constrained TKA, the PJI rate was significantly increased compared with unconstrained TKA (p < 0.0001). After 1 year, the PJI rate was 2.0% for constrained TKA and 0.8% for unconstrained TKA, as well as 3.1% and 1.4% respectively after 7 years. Implantation of a constrained TKA (HR = 2.55), male sex (HR = 1.84), an increased Elixhauser Comorbidity Index score (HR = 1.18-1.56) and an implantation volume of less than 25 UKA per year (HR = 2.15) were identified as risk factors for revision surgeries; an Elixhauser Comorbidity Index score of 0 (HR = 0.80) was identified as a preventive factor. CONCLUSIONS: A reduced implantation volume and constrained knee arthroplasty are linked to a higher risk of PJI. Comorbidities (increased Elixhauser Comorbidity Index score), male sex and a low UKA-implantation volume were identified as risk factors for PJI. Patients who fulfil these criteria need specific infection prevention measures. Further analyses are required to investigate the potential influence of prevention and risk factor modification. LEVEL OF EVIDENCE III.