Clinical differences between delayed and acute onset postoperative spinal infection

Spine surgeons often encounter cases of delayed postoperative spinal infection (PSI). Delayed-onset PSI is a common clinical problem. However, since many studies have investigated acute PSIs, reports of delayed PSI are rare. The purpose of this study was to compare the clinical features, treatment course, and prognosis of delayed PSI with acute PSI. Ninety-six patients diagnosed with postoperative spinal infection were enrolled in this study. Patients were classified into 2 groups: acute onset (AO) within 90 days (n = 73) and delayed onset (DO) after 90 days (n = 23). The baseline data, clinical manifestations, specific treatments, and treatment outcomes were compared between the 2 groups. The history of diabetes mellitus (DM) and metallic instrumentation at index surgery were more DO than the AO group. The causative organisms did not differ between the 2 groups. Redness or heat sensation around the surgical wound was more frequent in the AO group (47.9%) than in the DO group (21.7%) (P = .02). The mean C-reactive protein levels during infection diagnosis was 8.9 mg/dL in the AO and 4.0 mg/dL in the DO group (P = .02). All patients in the DO group had deep-layer infection. In the DO group, revision surgery and additional instrumentation were required, and the duration of parenteral antibiotic use and total antibiotic use was significantly longer than that in the AO group. Screw loosening, disc space collapse, and instability were higher in the DO group (65.2%) than in the AO group (41.1%) (P = .04). However, the length of hospital stay did not differ between the groups. Delayed-onset PSI requires more extensive and longer treatment than acute-onset surgical site infection. Clinicians should try to detect the surgical site infection as early as possible.