Spinal implant-associated infections: a prospective multicentre cohort study

•Most spinal implant-associated infections were acquired during surgery (98%) and presented within 6 weeks.•Late-onset infections presented mainly with persisting or increasing neck or back pain (71%).•Predominant pathogens were coagulase-negative staphylococci and Cutibacterium spp.•Sonication of removed implants was the most sensitive diagnostic method, mainly for late-onset infections.•Debridement and retention was performed in all infections with well-fixed implants. This study evaluated the clinical, laboratory, microbiological, radiological and treatment characteristics of patients with early-onset and late-onset spinal implant-associated infections. Patients diagnosed with spinal implant-associated infection between 2015–2019 were prospectively included and treated according to a standardised algorithm. Infections were classified as early-onset (≤6 weeks) and late-onset (>6 weeks). Among 250 patients, 152 (61%) had early-onset and 98 (39%) had late-onset infection. Local inflammatory signs was the most common manifestation in early-onset infections (84%), whereas late-onset infections presented mainly with persisting or increasing local pain (71%). Sonication fluid was more often positive than peri-implant tissue samples (90% vs. 79%; P = 0.016), particularly in late-onset infections (92% vs. 75%; P = 0.005). Predominant pathogens were coagulase-negative staphylococci, Staphylococcus aureus and Cutibacterium spp. Debridement and implant retention was the most common surgical approach in early-onset infections (85%), whereas partial or complete implant exchange was mainly performed in late-onset infections (62%). Of the 250 patients, 220 (88%) received biofilm-active antibiotics, and median treatment duration was 11.7 weeks. Moreover, 49 patients (20%) needed more than one revision for infection and six patients (2.4%) died during hospital stay. Concluding, most spinal implant-associated infections were acquired during surgery and presented within 6 weeks of surgery. Infections presented mainly with local inflammatory signs in early-onset and with persisting or increasing pain in late-onset infections. Sonication was the most sensitive microbiological method, particularly in late-onset infections. Debridement and implant retention was used in well-integrated implants without loosening, independent of the time of infection onset.