Shoulder Arthritis
Degenerative arthritis (i.e. osteoarthritis) of the shoulder occurs as the articular cartilage lining the glenohumeral joint (ball and socket) erodes, exposing the underlying bone. This can cause significant pain and loss of function. Although not as common as arthritis of the hip and knee, treatments are similar and based on managing the symptoms with oral medications (non-steroidal anti-inflammatories), activity modification, and physical therapy to maintain strength and range of motion.
When pain and disfunction no longer repond to conservative therapies, a total shouler replacement may be the solution. In a conventional total shoulder replacement, the "worn out" ball is resected and replaced with a metal ball (cobalt chrome). It is attahced to a "stem" which is then inserted into the upper end of the humerus. It is held in place with cement, or, in some cases, may be "press-fit" to fill the canal.
The socket or glenoid is resurfaced with a dense, plastic (polytethylene) insert, held in position by bone cement (polymethylmethacrylate).
An xray of a healthy, non-arthritic shoulder. Note the round contour of the proximal humerus. In addition, the space between the ball and socket is well maintained.
A standard xray depicting degnerative arthritis of the shoulder. Notice how the ball appears flattened and there is a complete loss of space between the ball and socket
A post-operative xray after conventional total shoulder replacement.
In some cases, a conventional total shoulder replacement may not acheive the goals of eliminating pain and restoring function. This is especially true in older individuals with chronic rotator cuff tears. For these patients, a so-called reverse or inverse total shoulder replacement may be appropriate. As the name implies, this device reverses the normal anatomic relationships by attaching a metal ball to the socket, and inserting a stem with a plastic (polyethylene) liner into the humerus.
A typical xray illustrating the changes seen in rotator cuff tear arthropathy. Notice how the flattened humeral head no longer sits balanced on the socket and has now shifted upward.
Post-operative films showing a reverse total shoulder arthroplasty. The metal ball is held on the socket with multiple screws. The arm is held in place against the ball by the pull of the deltoid muscle, which is also responsible for allowing genertating motion after surgery.