I was leading the pitch and placed what I thought was a solid DMM size 6 wallnut in the crack to protect the traverse which I was expecting to be run out from the description. On setting off on the traverse I knew there was a chance of taking a decent size lead fall onto that nut and I felt reassured by the placement. I found the last couple of moves of the traverse challenging and started tiring so attempted to down climb but in doing so made a semi controlled fall off expecting to swing and to be caught by the nut. Sadly the nut didn’t hold and I took a ground fall leading to a compression fracture of one of my vertebrae thankfully not requiring surgery