Spinal Infection Management With Structural Allograft

Spinal bone infections can involve the bone vertebra, intervertebral disc space, spinal canal and soft tissues. It generate neurological deficit in addition to the destruction of the bone that causes functional disability and significant pain (Colmenero 1997). Spinal infections include discitis, osteomyelitis, epidural abscesses, meningitis, subdural empyema, and abscesses of the spinal cord (An, 2006). Only discitis and osteomyelitis can occur together (Skaf, 2010). Vertebral osteomyelitis is the most frequent, affecting 2 to 7 patients per 100,000 habitants (Bhavan, 2010; Grammatico 2003).

Pathogenic organisms reach the column by hematogenous pathway, arterial pathways (Batson's plexus) or by direct inoculation, due to a diagnostic or therapeutic intervention (Skaf, 2010). The natural history of pyogenic vertebral infections involves an infectious source or an incident followed by a period of intense pain, with or without generalized significant sepsis. Neurological deficit is caused by: [1] direct extension of the infection in the form of an abscess or bacterial communication with the spinal canal to the neural elements or [2] secondary compression of a pathological fracture as a result of bone softening. (Campbell´s, 2013).

Early diagnosis and treatment are essential for optimal outcomes (Weisz, 2000). The treatment goals may include eradicating the infection, relieving pain, preserving or restoring neurologic function, improving nutrition, and maintaining spinal stability (Tay, 2002). The aim of this study is to demonstrate that the use of bone allograft is a functional method to stabilize the spine after a bone spinal infection.

METHODS This study was approved by our Institutional Ethics and Research Committee. Patients with vertebral bone destruction are randomized included in two groups. Inclusion criteria: patients older than 18 years, any gender, pyogenic spinal infection with bone destruction and kyphotic deformity, without previous treatment of any kind, and Informed Consent signature. Exclusion criteria: patients with immunodeficiency, psychiatric disorders, patients with severe malnutrition, morbid obesity. Elimination criteria: failure to comply with follow-up time, patient's express request to leave the study. The bone reconstruction will be performed in a one-step surgical procedure. All participants will undergo the same surgical procedure consisting of open surgery, more debridement of infected and devitalized tissue, as well as corresponding bone resection. For the identification of the microorganism, biopsies will be performed guided by computed tomography (CT scan) and/or by fluoroscopy. A culture and antibiogram will be performed in case of not obtaining enough material for this, at the time of the surgery samples will be sent to perform the same procedure. The investigators will use the appropriate antibiotics, according to infecting microorganism and result of antibiogram, and patients with infections with gram positive and negative microorganisms only will be included. Bone consolidation, pain, functionality, and spinal deformity will be evaluated.

The investigators will perform evaluations at 8, 12, 16, 20 and 24 weeks, and a CT scan will be realized, to evaluated the bone consolidation, defined as the presence of continuous trabeculae between the bone graft and the vertebra, according to the next classification system. Type 1 definitive fusion; Type 2 uncertain fusion; Type 3 definitive pseudoarthrosis.

Statistical analysis. The results will be reported in contingency tables, frequencies, percentages, measures of central tendency and dispersion. Qualitative variables will be analyzed with the chi-square statistic and quantitative variables with t-test for independent samples with a significance level of 95% with their respective confidence intervals, or with non-parametric statistics if necessary. Using a formula for hypothesis testing and difference of two proportions or with the proportion of a reference value, with a value zα of 1.94 with a level of significance of 95% for a queue, and a value zβ of 1.20 with a power of 80 %, With a proportion for group 1 of 0.38 and for group 2 of 0.83 (Zdeblick, Ducker) a sample of 19 participants was obtained per group. Statistical analysis will be performed with IBM SPSS version 20 (SPSS, Inc., Armon, NY).