A total shoulder replacement (total shoulder arthroplasty) is a surgical procedure designed to alleviate chronic pain and restore mobility in a severely damaged shoulder joint. The shoulder is a highly mobile ball-and-socket joint, where the rounded head of the upper arm bone (the humerus) fits into a shallow cavity in the shoulder blade (the glenoid). When the protective cartilage deteriorates, the resulting friction causes significant pain and stiffness. The goal of the replacement is to remove these damaged joint surfaces and replace them with artificial components (prostheses) to allow smooth, pain-free movement.
The Mechanics of Shoulder Replacement
The standard, or anatomic, total shoulder replacement involves substituting both the ball and the socket components of the natural joint. The damaged humeral head (the “ball”) is removed and replaced with a polished metal component attached to a stem inserted into the humerus. The materials used for this metallic ball and stem are strong, biocompatible alloys, such as cobalt-chrome or titanium.
The socket portion, the glenoid cavity, is resurfaced with a smooth, concave prosthetic component. This new socket is made from durable, specialized plastic (high-molecular-weight polyethylene), designed to articulate smoothly against the metal ball. In some cases, this plastic component is secured to the shoulder blade with cement. This hardware combination creates a new joint that mimics the original anatomy, aiming for natural motion and stability.
Conditions Requiring Total Shoulder Replacement
The need for a total shoulder replacement most often arises from conditions causing irreversible deterioration of the joint cartilage. The most frequent indication is severe osteoarthritis (wear-and-tear arthritis), where protective cartilage erodes, leading to painful bone-on-bone contact. This degeneration results in chronic pain resistant to non-surgical treatments like physical therapy or anti-inflammatory medications.
Other causes include inflammatory conditions like rheumatoid arthritis, where an overactive immune system attacks the joint lining, causing cartilage destruction. Severe fractures of the upper humerus that cannot be successfully repaired may also necessitate a total replacement. Avascular necrosis, or “bone death,” where the blood supply to the humeral head is disrupted, causing the bone to collapse, is another condition requiring surgical intervention.
Anatomic Versus Reverse Total Shoulder Replacement
The decision between the two main types of total shoulder replacement—anatomic and reverse—is based primarily on the health of the patient’s rotator cuff tendons. The anatomic total shoulder replacement (aTSA) is chosen when the rotator cuff is intact and functional. The procedure relies on these tendons to power and stabilize the joint, restoring the body’s natural configuration with the ball on the humerus and the socket on the glenoid.
The reverse total shoulder replacement (rTSA) is a biomechanically distinct option where the positions of the ball and socket are switched. A metallic ball (glenosphere) is fixed to the shoulder blade, and a plastic socket is placed on the humerus, reversing the joint’s structure. This reversal changes the center of rotation, allowing the large deltoid muscle to take over the function of a damaged or irreparable rotator cuff. The rTSA is indicated for patients with rotator cuff tear arthropathy or massive, irreparable tears, providing movement when natural stabilizing muscles are deficient.
Post-Surgical Recovery and Rehabilitation
Immediately following surgery, the arm is placed in a sling for four to six weeks to immobilize and protect the healing tissues. This initial protection allows the joint capsule and any repaired soft tissues, particularly in the anatomic procedure, to heal securely. Pain management during this phase is achieved through prescribed medications, including narcotics and non-steroidal anti-inflammatory drugs, supplemented by ice therapy.
Physical therapy (PT) is a necessary part of the recovery process, often beginning with gentle, passive range-of-motion exercises within the first few days to weeks. Passive motion means the therapist or the patient’s other hand moves the arm without using the shoulder muscles. After the initial protective phase (around six weeks), the program progresses to active motion and gradual strengthening exercises to rebuild muscle power. Adherence to the PT protocol is important, as the final outcome of mobility and function depends on the patient’s commitment, with a return to most activities occurring within six to twelve months.