Reportage in the orthopedic surgery operating theatre in Pasteur 2 Hospital, Nice, France. Medullary liberation and arthrodesis in a patient suffering from lumbar stenosis caused by arthritis. The operation consists of freeing boney elements from the vertebral canal that are compressing it, and consolidating the spine with an arthrodesis. This operation is carried out using the pre-op 3D imagery O-Arm system. Grinding the bone that was removed to free the vertebral canal. It will be grafted onto the bone and screws at the end of the operation (brone graft).