The skin and the strong Ligamentous cord attached to the poll are the essential things to cut, as the muscles can easily be torn across.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
Then the great Ligamentous cord above the spine is cut across at the farthest available point, together with the muscles above and below the spine.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
It is not uncommon for portions of bone to be torn off at the site of attachment of strong Ligamentous bands or tendons, constituting a "sprain fracture"; or for intra-articular cartilages to be torn and displaced, as in the knee.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson