Vertebral osteomyelitis after spine instrumentation surgery: risk factors and management

Background Vertebral osteomyelitis after spine instrumentation surgery (pVOM) is a rare complication. Most cases of infection occur early after surgery that involve skin and soft tissue and can be managed with debridement, antibiotics, and implant retention (DAIR). Aim To identify pVOM risk factors and evaluate management strategies. Methods From a multicentre cohort of deep infection after spine instrumentation (IASI) cases (2010–2016), pVOM cases were compared with those without vertebral involvement. Early and late infections were defined (<60 days and >60 days after surgery, respectively). Multivariate analysis was used to explore risk factors. Findings Among 410 IASI cases, 19 (4.6%) presented with pVOM, ranging from 2% (7/347) in early to 19.1% (12/63) in late IASIs. After multivariate analysis, age (adjusted odds ratio (aOR): 1.10; 95% confidence interval (CI): 1.03–1.18), interbody fusion (aOR: 6.96; 95% CI: 2–24.18) and coagulase-negative staphylococci (CoNS) infection (aOR: 3.83; 95% CI: 1.01–14.53) remained independent risk factors for pVOM. Cases with pVOM had worse prognoses than those without (failure rate; 26.3% vs 10.8%; P = 0.038). Material removal was the preferred strategy (57.9%), mainly in early cases, without better outcomes (failure rate; 33.3% vs 50% compared with DAIR). Late cases managed with removal had greater success compared with DAIR (failure rate; 0% vs 40%; P = 0.067). Conclusion Risk factors for pVOM are old age, use of interbody fusion devices and CoNS aetiology. Although the diagnosis leads to a worse prognosis, material withdrawn should be reserved for late cases or when spinal fusion is achieved.