Evaluating the effect of autologous bone graft impregnated with rifampicin and isoniazid on the rate of spinal fusion in a porcine animal model – A literature review

• The high prevalence of spinal tuberculosis in South Africa incurs considerable morbidity to those affected and adds a significant cost burden to the public health sector. • The application of anti-tubercular drugs to the bone graft used in patients with spinal tuberculosis undergoing spinal surgery has never been performed and as such is currently unsafe for in vitro human application. • This literature review provides the framework for an in vitro animal study using a porcine model, which if safe and demonstrates benefit, will be expanded in our department to the in vitro human model in patients with spinal tuberculosis. Tuberculosis is a disease of poverty with a global concentration in sub-Saharan Africa. While 10% of extra-pulmonary tuberculosis is skeletal, 50% of this occurs in the spinal column. Besides the surgical management of spinal tuberculosis, medical management is an important adjunct. In surgical candidates, interventions commonly involve drainage of any pre- and para -vertebral tuberculous abscesses, debridement of devitalized necrotic vertebral tissue, an instrumented or non-instrumented anterior spinal column construction and fusion, augmented by an instrumented or non-instrumented lateral or posterolateral spinal fusion. To date no clinical control study has ever been conducted to evaluate the effect of a mixture of morselized autologous bone graft and the ceramic bone graft substitute calcium phosphate, impregnated with a single equivalent weight-adjusted oral dose of rifampicin and isoniazid in a ratio of 2:1, as characterizes a single human oral dose, on the rate of spinal fusion, when used as an on lay in the context of achieving a single level non-instrumented posterolateral spinal fusion, in neither a human nor porcine animal model. Due to the effects of local anti-tubercular antibiotic therapy currently being unknown, and therefore unsafe for in vitro human application, our literature review aimed to evaluate the current state of knowledge on what would be the effect of an interventional mixture of morselized autologous bone graft and ceramic bone graft the substitute, namely calcium phosphate paste, impregnated with a single equivalent weight-adjusted oral dose of rifampicin and isoniazid, on the rate of posterolateral spinal fusion in a porcine animal model. We hope that this literature review will be followed by an in vitro animal study using a porcine model, which if safe and demonstrates benefit, could be expanded to the in vitro human model in patients with spinal tuberculosis who meet criteria for surgical intervention.