Schematic illustration of bioreactors utilized in BTE. Specifically, (A) spinner (red arrows show movement of the stir bar), (B) rotating wall (red arrows show movement of the vessel), and (C) perfusion bioreactors (red arrows show movement of the medium) are the most commonly used. (D) Comparison of bioreactor culture of bone constructs (right) versus static culture (middle). Bioreactors allow for increased nutrient perfusion throughout construct, and enhanced bone formation in vitro. Adapted from Martin et al. and Olivier et al.321,322