Artwork needs a spine, just like you need your spine. You are not about your spine, but without it you would be a puddle on the floor. Your painting also needs a spine to hold it together, to give it stability. Your painting is not about the spine or structure, but the spine needs to be there in order to stabilize it. Try studying your favourite artwork by your favourite artist – practice looking for and identifying the spine…. you may find that they use multiple spines. Then come back and look at your own artwork – look for the spine. If you can’t find one “impose” one.