It sounds like you are talking about a special type of suture used to reattach a torn tendon in the shoulder. It's made of bone and is pushed through the tendon into the bone.

Studies were done on this type of anchor to find out how strong it was. First it was tested out on cadavers (human bodies saved after death for scientific study). Scientists could find out how much load it can take by putting more and more force against the anchor until it did break.

When the bone was too thick for the anchor to go in, an awl was used to make a tiny pilot hole. Then a surgical hammer or mallet was used to drive the anchor into the bone. During testing there were no problems with breakage.