The patient is usually placed in a sidelying position when the surgeon suspects a tear in the posterior labrum. Posterior refers to the back of the shoulder joint.
The labrum is a rim of dense, fibrous cartilage that is attached to the shoulder socket. The labrum helps form a deeper cavity for the head of the humerus (upper arm bone) to fit into.
Sometimes the labrum tears away from the bone and takes a piece of the bone with it. The surgeon must lift the labrum up, smooth the bone underneath, and then reattach the cartilage. Traction is needed in order to help the surgeon see inside the joint and access the damaged areas.
A special arm traction device is used. It places the arm in the position needed by the surgeon and holds it there during the operation. A small amount of weight (usually 10 pounds) is used. This is not enough to dislocate the shoulder. This technique is safe for the patient and effective for the surgeon.