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). Deeper involvement of bone structures may present different risk factors and may require a different approach.

AIM: We aimed to identify its risk factors and evaluate management strategies.

METHODS: From a multicenter cohort of deep infection after spine instrumentation (IASI) cases (2010-2016), we compared pVOM cases 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 etiology. Although the diagnosis leads to a worse prognosis, material withdrawn should be reserved for late cases or when spinal fusion is achieved.