Reverse Total Shoulder Replacement

Reverse Total Shoulder Replacement (rTSA) is a specialized surgical procedure that has transformed the management of patients with severe shoulder damage, especially those with rotator cuff injuries. This operation differs significantly from a conventional shoulder replacement, both in design and biomechanics, offering new hope to patients who previously had limited treatment options.

What Is Reverse Total Shoulder Replacement?

In a healthy shoulder, the ball (humeral head) fits into a shallow socket (glenoid) like a golf ball on a tee. Traditional shoulder replacements mimic this anatomy. However, reverse shoulder arthroplasty “reverses” this relationship—the ball is placed where the socket used to be (on the shoulder blade), and the socket is placed where the ball used to be (on the arm bone).

This reversal dramatically alters how the shoulder works. Instead of depending on the rotator cuff muscles (which may be torn or non-functional), the reverse design shifts much of the workload to the deltoid muscle—the large muscle over the shoulder.

Biomechanical Advantages of rTSA

1. Preventing Superior Migration

In patients with a torn rotator cuff, the humeral head often shifts upward due to unbalanced forces, resulting in pain and loss of motion. The rTSA design includes a spherical glenoid component, called a glenosphere, which acts as a “mechanical stop,” preventing this upward migration during movement.

2. Creating a Stable Fulcrum

Normally, the rotator cuff keeps the humeral head centered in the socket through a mechanism called “concavity compression.” With rTSA, stability is restored through a fixed mechanical fulcrum. This allows the deltoid to elevate and rotate the arm efficiently—even in the absence of a functioning rotator cuff.

3. Improved Deltoid Efficiency

One of the most critical innovations in rTSA is medializing and lowering the center of rotation (CoR) of the shoulder. This change increases the deltoid’s “moment arm,” giving the muscle more leverage to move the arm with less effort. Essentially, rTSA makes the deltoid stronger by giving it a better angle to work from.

Potential Drawbacks of rTSA

Despite its advantages, rTSA is not without trade-offs.

• Medialization of the humerus can shorten the rotator cuff, reducing strength in internal and external rotation.
• Inferior translation (lowering) of the humerus may overstretch the deltoid, potentially leading to acromial or scapular fractures.
• The altered mechanics may also reduce the shoulder’s range of motion compared to a natural joint.

The Grammont Revolution

In the 1980s, French surgeon Paul Grammont introduced the concept of a medialized fixed-fulcrum shoulder prosthesis. His design, the Delta III, placed the center of rotation directly on the glenoid surface. This innovation dramatically increased the deltoid’s mechanical advantage and reduced stress on the implant-bone interface, making reverse shoulder replacement a reliable solution for previously untreatable conditions.

Modern Design Considerations

While all modern rTSA devices descend from Grammont’s original concept, manufacturers have developed variations to address specific complications:

• Lateralization of the CoR: Moves the ball outward to reduce scapular notching—a condition where the humeral socket rubs against the shoulder blade.
• Onlay humeral designs: Increase humeral offset, tensioning the remaining rotator cuff and improving joint stability.
• Different humeral neck angles: Adjust joint orientation to optimize motion and reduce impingement.

Figures in the original article (e.g., Figure 4) show how modifying the humeral or glenoid position affects deltoid force and joint function.

Stability and Deltoid Wrapping

The deltoid wraps around the humerus, providing a stabilizing force. Designs that lateralize the humerus increase this wrapping, improving stability. In contrast, excessive medialization may eliminate this wrapping, even causing the deltoid to pull the humerus away from the joint—a source of instability, especially in patients with significant bone loss.

Classification of rTSA Designs

Modern rTSA prostheses can be classified based on the position of the glenoid and humeral components:

Glenoid Type	Humeral Type	Classification	Description
Medialized	Medialized	MG/MH	Grammont-style; highest deltoid efficiency but lower stability
Lateralized	Medialized	LG/MH	Better stability and rotator cuff tension; slightly less deltoid efficiency
Medialized	Lateralized	MG/LH	Balanced design; better rotation and wrapping
Lateralized	Lateralized	LG/LH	Most lateralized; may risk fractures

Positioning Matters

Even with the best implant design, surgical technique is critical. Positioning the baseplate too high or tilting it incorrectly can lead to complications like scapular notching, instability, or implant loosening. Similarly, choosing the right angle for the humeral component (typically 30° of retroversion) is essential for restoring rotation.

Individualized for Each Patient

Each patient’s anatomy, bone quality, and muscle strength influence surgical decisions. For example, patients with:

• Medial glenoid erosion may require bone grafts or augmented baseplates to restore the joint line.
• Humeral bone loss may need special prostheses to reconstruct the greater tuberosity and maintain deltoid efficiency.
• Smaller frames or osteoporosis may need implants that avoid over-tensioning to prevent fractures.

Indications and Expanding Use

Initially developed for rotator cuff arthropathy, rTSA is now also used for:

• Massive rotator cuff tears without arthritis
• Failed shoulder replacements
• Rheumatoid arthritis
• Fractures of the proximal humerus
• Complex revisions with bone loss

Potential Complications

Although rTSA outcomes are generally excellent, some risks include:

• Acromial or scapular stress fractures from over-tensioning the deltoid
• Scapular notching due to mechanical impingement
• Instability, especially without adequate deltoid or subscapularis tension
• Nerve injuries from over-lengthening or surgical positioning
• Infections, particularly in revision cases

Summary

Reverse Total Shoulder Replacement is a powerful and proven tool in orthopedic surgery. By reversing the mechanics of the shoulder joint, it allows patients with complex rotator cuff injuries and joint damage to regain function, reduce pain, and return to daily activities. Success depends not only on the implant design but also on careful surgical technique and tailoring the approach to each patient’s unique anatomy and needs.

 

Do you have more questions?

Q. What is a reverse total shoulder replacement?
A. A reverse total shoulder replacement is a surgical procedure where the normal ball-and-socket structure of the shoulder is reversed, placing the ball component on the shoulder blade and the socket on the upper arm bone.

Q. When is reverse total shoulder replacement recommended?
A. It is recommended for patients with severe shoulder arthritis combined with a massive rotator cuff tear or for those who have had failed shoulder surgeries.

Q. How does reverse shoulder replacement differ from traditional shoulder replacement?
A. In reverse shoulder replacement, the ball and socket positions are switched to allow the deltoid muscle to lift the arm, compensating for a deficient rotator cuff.

Q. What conditions does reverse total shoulder replacement treat?
A. It treats cuff tear arthropathy, severe arthritis with rotator cuff tears, complex fractures, failed prior shoulder replacements, and certain shoulder tumors.

Q. What are the main components used in a reverse total shoulder replacement?
A. The procedure uses a metal ball attached to the shoulder blade and a plastic socket attached to the upper arm bone.

Q. What are the goals of reverse total shoulder replacement?
A. The goals are to relieve pain, improve shoulder function, and restore the ability to lift the arm using the deltoid muscle.

Q. Who is a candidate for reverse total shoulder replacement?
A. Candidates include patients with non-functioning rotator cuffs, severe shoulder arthritis, previous failed surgeries, or complex fractures.

Q. What is the recovery time for reverse total shoulder replacement?
A. Recovery typically takes several months, with initial healing over a few weeks followed by physical therapy for gradual return to function.

Q. What kind of anesthesia is used during the surgery?
A. General anesthesia, sometimes combined with a regional nerve block, is used during reverse total shoulder replacement.

Q. How long does the surgery take?
A. The surgery usually takes about one to two hours.

Q. What are the possible complications of reverse total shoulder replacement?
A. Complications may include infection, dislocation, nerve injury, implant loosening, or fracture.

Q. What type of physical therapy is required after surgery?
A. Physical therapy involves gradual range-of-motion exercises followed by strengthening exercises as healing progresses.

Q. Will I regain full range of motion after the surgery?
A. Most patients experience significant improvement in function and pain relief, but full range of motion may not be restored.

Q. Can reverse total shoulder replacement be done on both shoulders?
A. Yes, but typically not at the same time. The second shoulder may be operated on after the first has healed.

Q. How long do the implants last?
A. Implants typically last 10 to 15 years or more, depending on activity level and other factors.

Q. What activities can I do after reverse shoulder replacement?
A. Most patients can return to daily activities and light recreational activities, but high-impact or heavy lifting should be avoided.

Q. What is the success rate of reverse total shoulder replacement?
A. The procedure has a high success rate in reducing pain and improving shoulder function, especially in patients with cuff tear arthropathy.