Shoulder Arthroplasty Explained: Anatomic and Reversed Replacement

A Shoulder Replacement or ‘Shoulder Arthroplasty’ procedure is an effective treatment for pain, loss of range of motion, and decreased function in patients with advanced shoulder arthritis. Shoulder replacement patients are expected to experience early and predictable pain relief, with improving range of motion and function occurring in the months following surgery, as they work through a physical therapy program. An initial period of immobilization in a sling is required, followed by progressive stretching, range of motion work, and strengthening.


Shoulder replacements can be divided into two main types, ‘anatomic’ or ‘reverse’ type procedures. The choice between the two is dependent upon the function of the individual patient’s rotator cuff musculature, with a ‘reverse’ replacement required in the setting of rotator cuff tearing or dysfunction.


The rotator cuff is comprised of four muscles that are the main stabilizers of the ball and socket of the shoulder or ‘glenohumeral joint.’ When absent, shoulder motion, especially overhead and out-to-the-side, can become difficult or absent altogether. In Anatomic Replacement surgery, the normal ball and socket configuration of the shoulder is maintained, relying on the rotator cuff musculature to allow for motion.


By contrast, in a Reverse Replacement the ball and socket orientation of the shoulder is ‘reversed’, placing the concave socket at the end of the arm or humerus bone, while creating a convex ball in the previous socket or glenoid of the shoulder. This shift in mechanical orientation alters the axis of the shoulder joint, allowing the Deltoid Muscle to assume control of the majority of motion. Since the deltoid is located outside of the shoulder joint, along the point of the top of the arm, it is able to provide motion following a reverse replacement, even in the absence of a functioning rotator cuff.


            Reverse replacements are also a bit more stable in than the ball-and-socket orientation of the native shoulder. This property makes a reverse ideal for patients with concerns about falls or dislocations, as well as those being treated with a shoulder replacement following an upper arm fracture.

Ultimately, the decision to proceed with any shoulder arthroplasty – reversed or anatomic – should take into account the individual problems, functional level, and goals of a patient on a case-by-case basis. In either case, proper selection of the correct replacement procedure can provide marked improvements in quality of life for those suffering from an arthritic shoulder.  

Elan Golan, MD

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