Reverse Shoulder Replacement: Disadvantages, Complications, and Functional Limitations

What are the disadvantages of reverse shoulder replacement?

While reverse shoulder replacement offers significant benefits for specific complex shoulder conditions, it carries distinct disadvantages including a higher risk of surgical complications like infection and nerve damage, prosthetic-specific issues such as scapular notching and glenoid loosening, and potential long-term functional limitations, particularly in internal rotation and overhead lifting capacity.

Understanding Reverse Shoulder Replacement

Reverse shoulder arthroplasty (RSA) is a specialized surgical procedure designed to alleviate pain and restore function in individuals with severe shoulder pathology, particularly those with rotator cuff arthropathy (arthritis combined with a massive, irreparable rotator cuff tear) or failed conventional shoulder replacements. Unlike traditional shoulder replacement, where a ball is placed on the humerus and a socket on the scapula, RSA reverses this anatomy: a metal ball (glenosphere) is fixed to the shoulder blade (scapula), and a plastic socket (humeral cup) is attached to the upper arm bone (humerus). This anatomical reversal repositions the center of rotation, allowing the deltoid muscle to compensate for the non-functional rotator cuff, thereby improving arm elevation. While remarkably effective for its intended indications, RSA is not without its drawbacks.

Surgical Complications

As with any major surgical procedure, reverse shoulder replacement carries inherent risks during and immediately following the operation.

• Infection: Despite meticulous sterile techniques, infection remains a serious complication, potentially requiring further surgery, prolonged antibiotic therapy, or even removal of the prosthetic components. Deep infections can be particularly challenging to eradicate.
• Nerve Damage: The intricate network of nerves around the shoulder (e.g., brachial plexus, axillary nerve) is susceptible to injury during surgery. This can lead to temporary or permanent weakness, numbness, or paralysis in the arm and hand.
• Fracture: Intraoperative fractures of the humerus or scapula can occur during component implantation. Post-operative periprosthetic fractures around the implants are also a risk, often requiring additional surgical intervention.
• Dislocation: The reverse design, while stable in many planes, can be prone to dislocation, particularly in specific positions or with certain movements. This risk is generally higher than with conventional total shoulder arthroplasty.
• Hematoma and Bleeding: Excessive bleeding during or after surgery can lead to the formation of a hematoma (a collection of blood), which may require drainage.
• Anesthesia Risks: General risks associated with anesthesia, such as adverse reactions to medications, respiratory complications, or cardiovascular events, are also present.

Prosthetic-Specific Complications

The unique design of the reverse shoulder prosthesis introduces specific complications related to the implants themselves and their interaction with surrounding tissues.

• Scapular Notching: This is one of the most common and unique complications of RSA. It occurs when the humeral cup impinges on the inferior border of the scapular neck during adduction and internal rotation, leading to erosion or "notching" of the bone. While not always symptomatic, severe notching can contribute to pain, implant loosening, and reduced range of motion.
• Glenoid Loosening: The glenosphere, fixed to the scapula, is subjected to significant shear forces. Over time, the fixation of the glenosphere to the scapula can loosen, leading to pain and implant failure, often requiring revision surgery. This is particularly relevant in patients with poor bone quality.
• Humeral Loosening: While less common than glenoid loosening, the humeral component can also loosen from the humerus, leading to similar symptoms and the need for revision.
• Component Wear: Although the materials are durable, the polyethylene liner in the humeral cup can wear down over many years, potentially releasing wear particles that can cause inflammation or osteolysis (bone loss), leading to loosening.
• Heterotopic Ossification: The abnormal formation of bone in soft tissues around the joint can occur, potentially restricting movement and causing pain.

Functional Limitations and Long-Term Outcomes

While RSA significantly improves function for its intended recipients, it does come with certain functional compromises and long-term considerations.

• Limited Internal Rotation: A common trade-off with RSA is a noticeable decrease in internal rotation range of motion. Activities like reaching behind the back (e.g., tucking in a shirt, fastening a bra) can become challenging.
• Impaired Lifting Capacity and Endurance: While the deltoid can elevate the arm, the absence of a functional rotator cuff means that the fine control and endurance for repetitive or heavy overhead lifting may be compromised compared to a healthy shoulder. Patients often report difficulty with sustained overhead activities.
• Residual Pain: While many patients experience substantial pain relief, some may still have persistent or new onset pain, which can be due to various factors including muscle imbalances, nerve irritation, or progressive joint changes.
• Revision Surgery: The lifespan of a reverse shoulder replacement, though improving, is generally considered shorter than that of a conventional total shoulder replacement. Factors like patient age, activity level, and the development of complications can necessitate revision surgery after several years. Each revision surgery carries increased risks and technical difficulty.
• Prolonged Rehabilitation: The recovery period after RSA is often extensive and demanding, requiring dedicated physical therapy to maximize functional gains and prevent stiffness.
• Altered Biomechanics: The reversed anatomy fundamentally alters the shoulder's biomechanics, which, while beneficial for elevation, can put increased stress on surrounding muscles and tendons, potentially leading to secondary issues.

Patient-Specific Considerations

The suitability and potential disadvantages of RSA are also heavily influenced by individual patient factors.

• Age and Activity Level: Younger, more active patients may place greater demands on the prosthesis, potentially increasing the risk of wear and loosening over time.
• Bone Quality: Patients with osteoporosis or poor bone quality are at higher risk for intraoperative fractures and implant loosening, particularly of the glenoid component.
• Comorbidities: Underlying health conditions such as diabetes, obesity, cardiovascular disease, and smoking can significantly increase the risk of surgical complications like infection and delayed wound healing.
• Pre-existing Muscle Weakness: While the deltoid compensates, severe deltoid weakness or pathology can compromise the functional outcome of RSA.

Weighing the Benefits Against the Risks

Reverse shoulder replacement is a powerful tool for restoring function and alleviating pain in specific, often debilitating, shoulder conditions. For many patients, particularly those with rotator cuff arthropathy, it offers a quality of life that would otherwise be unattainable. However, it is crucial for patients and healthcare providers to have a comprehensive understanding of the inherent disadvantages, including surgical and prosthetic-specific complications, as well as potential long-term functional limitations. A thorough pre-operative assessment, realistic patient expectations, and a clear understanding of the trade-offs are paramount in making informed decisions about this complex yet often life-changing procedure.