Bone graft scaffold arrangements are described that can be used in minimally invasive posterolateral spinal fusion. The bone graft scaffold apparatus comprise a housing which comprises a cavity for receiving bone growth promoting materials and a plurality of apertures. In use these allow bone and blood vessels to grow through the plurality of apertures to form the bone bridge between vertebrae. Further the bone graft scaffold apparatus comprise at least one opening in the housing for receiving a shaft of an orthopaedic device, such as rod linking pedicle screws, or the shaft of a pedicle screw, or another suitable shaft in another surgical procedure. The apparatus can be attached to structural components such as rods and screws and used to form a continuous scaffold between vertebras to assist in forming a bone bridge.