Incidence and risk of delayed surgical site infection following instrumented lumbar spine fusion

• Delayed infection following spine surgery is relatively rare.
• Most patients with a late infection have a chronic infection at a distant site.
• The use of prophylactic antibiotics is recommended by a minority of spine surgeons.
• Some high risk patients may benefit from antibiotics before invasive procedures.

We reviewed a retrospective case series of patients with delayed infections after spinal fusion, and surveyed medical experts in Canada and the USA regarding their use of prophylactic antibiotics for patients undergoing invasive procedures following spine surgery. Infections after spinal fusion are a relatively common complication, which typically occur early in the postoperative period. Infections which occur more than 3 months from the index procedure are rare and are often caused by atypical pathogens. The proportion of infections that required debridement and occurred 6 months after the index procedure was 4.3% (7/162). Over 85% of these infections were polymicrobial, with one third of those containing methicillin-resistant Staphylococcus aureus. The most common operative indications were either trauma or tumour, and most patients with a delayed infection had a distant chronic infection. The majority of spine experts do not routinely recommend prophylactic antibiotics for invasive procedures after spine fusion. In the multivariate analysis, experts were more likely to recommend antibiotics for patients undergoing a non-dental procedure, those who were diabetic, and those who were greater than 1 year out from their procedure. In summary, the delayed presentation of infection after instrumented spinal fusion is a rare but serious complication. However, due to its infrequency, routine prophylaxis to prevent haematogenous seeding is likely unnecessary.