Clinical and financial burden of spinal infections in people who inject drugs

Background People who inject drugs (PWID) are known to be at increased risk of infectious diseases including bacterial and blood-borne viral infections. However, there is limited literature surrounding the burden of spinal infections as a complication of injecting drug use (IDU). Aims To quantify the clinical and financial burden of IDU-related spinal infections. Methods Retrospective chart review of adult PWID with spinal infections requiring hospital admission to a tertiary health service in Melbourne, Australia between 2011 and 2019. Results Fifty-seven PWID with 63 episodes of spinal infections were identified with a median hospital stay of 47 days (interquartile range (IQR) 16; range 4-243 days). One-third of episodes required neurosurgical intervention and 11 (17%) episodes required intensive care unit admission (range 2-17 days). Staphylococcus aureus was the most common causative pathogen, present in three-quarters of all episodes (n = 47). The median duration of antibiotic regime was 59 days (IQR 42) and longer courses were associated with known bacteraemia (P = 0.048), polymicrobial infections (P = 0.001) and active IDU (P = 0.066). Predictors of surgery include neurological symptoms at presentation (relative risk (RR) 2.6; P = 0.010), inactive IDU status (RR 3.0; P = 0.002), a diagnosis of epidural abscess (RR 4.1; P = 0.001) and spinal abscess (RR infinity; P < 0.001). Completion of planned antimicrobial therapy was reported in 51 (82%) episodes. Average expenditure per episode was A$61 577. Conclusions Spinal infections in PWID are an underreported serious medical complication of IDU. Although mortality is low, there is significant morbidity with prolonged admissions, large antimicrobial requirements and surgical interventions generating a substantial cost to the health system.