Overview of Reverse Shoulder Arthroplasty
Reverse total shoulder arthroplasty (RTSA) – or reverse shoulder replacement surgery – is a surgical procedure that is used around the world to treat a range of shoulder problems. These problems include traumatic injuries and age-related wear and tear, and particularly, situations where the “rotator cuff” – a group of muscles and tendons that stabilize the shoulder, is damaged and can’t be repaired.
The frequency of this surgery has been on the rise, especially in the United States. In 2011, about 22,835 of these surgeries were performed, but by 2017, this number had grown to 62,705.
This technique was first put forward by doctors named Beddow and Alloy back in 1970, but they didn’t share the results of their work. The first reported cases in which this method was used were in 1987 by a team led by a doctor named Grammont. They treated 8 patients who suffered from rotator cuff arthropathy – a medical term for shoulder joint damage due to a torn rotator cuff. They used an early version of the RTSA device called the “Trompette.”
The Reverse total shoulder arthroplasty reached the United States of America in 1998, after being used in Europe for several years.
What’s unique about the RTSA is the way it’s designed. In a normal shoulder joint, there’s a rounded head at the top of your upper arm bone that fits into a shallow socket in your shoulder blade. But in the RTSA procedure, this setup is reversed – the ball part is attached to the shoulder blade, and a new, cup-like socket is attached to the upper arm bone instead.
Anatomy and Physiology of Reverse Shoulder Arthroplasty
The shoulder joint is a complex structure that includes four different joint connections: the acromioclavicular joint, the glenohumeral joint, the sternoclavicular joint, and the scapulothoracic joint. Knowing how your shoulder works is important for doctors to choose the right shoulder replacement (prosthesis) and for the successful treatment.
The Glenohumeral (GH) Joint is particularly important in shoulder function. This joint, where your upper arm bone (humeral head) meets with a recess in your shoulder blade (the bony glenoid), allows for a wide range of movement. It is kept stable by what we call “dynamic” and “static” stabilizers. Dynamic stabilizers are muscles and tendons that help keep things in place when your shoulder moves. These include the long head of the biceps and the rotator cuff muscles. Static stabilizers, on the other hand, are parts of the shoulder that keep things stable when not in motion, such as the shape of the glenoid joint, shoulder joint capsule, and ligaments.
In a type of shoulder replacement called Reverse Total Arthroplasty (RTSA), the center of shoulder rotation is moved slightly down and towards the middle of the body. Because of this shift, the deltoid muscle, a large muscle on the shoulder, is able to move the arm more efficiently. Plus, the shoulder has a larger surface area after RTSA, improving stability and potential movement range. Lastly, it helps minimize upward movement of the upper arm bone which usually occurs with rotator cuff disease, hence improving shoulder stability.
Why do People Need Reverse Shoulder Arthroplasty
Reverse Total Shoulder Arthroplasty (RTSA) is a surgical procedure used to treat various shoulder conditions. Here are some of the conditions that this surgery is commonly used for:
1. Rotator cuff arthropathy: This is a condition where the shoulder joint becomes worn out and painful due to a large tear in the rotator cuff muscles, leading to swelling and arthritis in the shoulder joint – specifically, the glenohumeral joint and the top part of the humerus bone (which is the long bone in your upper arm).
2. Pseudo-shoulder paralysis: In some cases where there is a large tear in the rotator cuff muscles that can’t be repaired, it can make you feel as though you cannot move your shoulder at all – thus resembling paralysis.
3. Severe fractures of the upper arm bone (proximal humerus fractures): If there has been a break in three or four parts of the top part of the humerus, RTSA can help treat this.
4. Post-traumatic glenohumeral arthritis: This is arthritis in the main shoulder joint that has been caused by an injury.
5. Chronic irreducible shoulder dislocation: This is a condition where the shoulder is consistently out of its socket and cannot be properly put back into place.
The RTSA procedure may also be done if previous shoulder surgeries (such as a total shoulder arthroplasty or a proximal humerus hemiarthroplasty) did not work as expected. In other instances, it may be recommended for inflammatory joint conditions like rheumatoid arthritis, which causes pain and swelling in the joints.
When a Person Should Avoid Reverse Shoulder Arthroplasty
There are some circumstances in which Reverse Total Shoulder Arthroplasty (RTSA), a type of shoulder replacement surgery, is not advised for patients. These include:
If a person has axillary nerve palsy, a condition affecting the nerve that supplies the deltoid muscle in the shoulder, surgery might not be suitable.
The deltoid muscle plays a large role in arm movement, so someone with a significantly weakened or missing deltoid muscle might not be a good candidate for this surgery.
If the patient has an active infection, they may need to wait until it clears up before having this procedure. This is because infections can cause serious complications during surgery.
If the patient has significant lack of bone in the glenoid – the part of the shoulder blade where it connects with the upper arm bone – RTSA may not be suitable. The glenoid is needed as it’s where the artificial joint will be attached.
The surgery is also not suitable for those with skeletal immaturity, which means their bones haven’t fully grown or developed.
Lastly, if someone has a neuromuscular disorder – a condition where the nerves that control the voluntary muscles are not working properly – there is an increased risk of the artificial joint coming out of place, making surgery a riskier option.
Equipment used for Reverse Shoulder Arthroplasty
In the past, the initial designs for the constrained RTSA prosthesis, a type of shoulder joint replacement, did not work out, so they had to be withdrawn due to the high incidence of failure. In 1981, a team led by Grammont came up with the idea of moving the rotation center of the humeral head (the ball part of the ball-and-socket shoulder joint) towards the body to improve the functioning of the deltoid muscle, the big muscle that shapes your shoulder.
In 1991, there was a significant improvement in the RTSA prosthesis design. This new design remained unchanged for about 15 years. It had two main upgrades: making the glenoid component (part of the shoulder joint where the ball articulates, like the socket in a ball-and-socket joint) bigger and rounder and tilting the humeral component (the ball part of the shoulder joint) to a sharper angle relative to the arm’s shaft (155 degrees to be precise).
By making the glenoid component bigger, the rotation center was moved inwards. This, together with a bigger humeral neck-shaft angle (angle between the arm and the ball of the shoulder joint), lowered the rotation center of the upper arm and increased the tension of the deltoid muscle. However, this new prosthesis design had its own set of problems like scapular notching (damage to the bone of the scapula), bone impingement (bones in the shoulder touching in a way they shouldn’t), and wearing out of polyethylene (a type of plastic used in the prosthesis).
Over the past 20 years, further modifications have been made to this design to address these problems. For example, decreasing the neck-shaft angle to 135 or 145 degrees has helped reduce the incidence of bone impingement and scapular notching. As a result, there are many different types of RTSA prostheses available today, all with different designs.
Usually, an RTSA prosthesis involves the following components: a cementless glenoid base plate; seated on the prepared glenoid and fixed by multidirectional screws, a mostly spherical modular geosphere secured at the glenoid base plate, and a humeral stem inserted into the prepared humerus. There are two types of stems available: cemented and cementless press-fit stems. On top of the humeral stem, a humeral cup is fitted. It is designed to secure a concave insert, made from polyethylene, on top of it. It is concave and articulates with, or fits into, the geosphere.
Who is needed to perform Reverse Shoulder Arthroplasty?
To safely carry out a procedure known as ‘reversed shoulder arthroplasty’ which is a type of shoulder replacement surgery, a team of various medical professionals is necessary. This team typically includes:
An ‘anesthetist’, who’s job is to administer anesthesia so you won’t feel any pain during the surgery, assisted by the ‘anesthetist assistant’.
A ‘scrub nurse’ who assists the surgeon by providing the necessary tools during the operation and helps maintain a sterile environment.
An ‘operative room runner’ who is there to ensure that everything runs smoothly during the operation by fetching any items or tools that may be needed.
The ‘shoulder surgeon’ who is a specialist doctor who performs the surgery, aided by the ‘surgeon assistant’.
A ‘recovery nurse’ who looks after you after the surgery helping control pain, monitor vital signs, and manage any side effects from the surgery or anesthesia.
Sometimes, a ‘prothesis company representative’ might also be present. This is optional and usually only happens if the surgical team is not familiar with the surgical instrument kit and the different parts of the prosthesis, which is the artificial device that will replace your shoulder joint. The representative’s job is to help identify these parts.
Preparing for Reverse Shoulder Arthroplasty
Before a patient undergoes a Reverse Total Shoulder Arthroplasty (RTSA), or shoulder replacement surgery, the doctor needs to gather a lot of information in order to best prepare for the procedure.
The first step in preparation for surgery is knowing the patient’s history. This means understanding a person’s lifestyle, medical conditions, and personal and work habits. This is important to determine how quickly the person might recover after surgery. For instance, individuals who live alone or need to use walking aids would need more help after the surgery.
The physical examination of the patient is another vital step. This involves checking the movement range of the shoulder, reviewing the condition of the rotator cuff (a group of muscles and tendons that hold the shoulder joint together), ensuring the axillary nerve (nerve which helps in moving your shoulder and arm) is functioning well, studying the functioning of the deltoid muscle (the muscle forming the rounded contour of the shoulder), and checking the skin condition over the shoulder. The doctor would also need to review the general health of the entire arm.
Now comes the imaging part, which involves taking multiple pictures of your shoulder using different medical equipment.
Standard X-rays are taken first. These pictures help the doctor plan the surgery, spot any issues with the shoulder bones, and evaluate the overall quality of the bones.
Next, the patient undergoes a Computed Tomography (CT) Scan. They’re like X-rays but much detailed. They help the doctor understand how much of the shoulder bone (humerus and glenoid) is available for the surgery and plan it accordingly. A type of CT scan called a 3D-CT scan can help decide if the shoulder surgery would bring the needed results.
Magnetic Resonance Imaging (MRI) Scan can also be needed. This type of imaging study gives a detailed picture of your rotator cuff. It helps the doctor understand the health and integrity of this part of your shoulder before the operation.
Finally, the patient’s medical health needs to be optimized. This includes understanding and managing any other medical conditions, like diabetes, anemia, heart or kidney diseases. This is vital in the recovery phase after the operation. The doctor reviews the patient’s medications and makes any necessary changes to get them ready for the surgery.
How is Reverse Shoulder Arthroplasty performed
The process of reversed total shoulder replacement (RTSA), a type of shoulder replacement surgery, typically begins with anesthesia. The anesthesiologist will usually administer both general anesthesia and a regional nerve block for the shoulder area. This will make you unconscious and numb in the shoulder region, so you won’t feel any pain during the surgery. In addition, antibiotics will be given directly into your veins to prevent any infection.
You will be seated in a ‘beach chair’ position on the operating table. Your chest will be raised to a 60-degree angle, with your shoulder at the edge of the table. This position will allow your arm to fully extend and provide the surgeon with a clear view of your shoulder. The anesthesia team will be on the opposite side of the table to ensure there’s enough room for the surgical team.
Once you’re unconscious and numbed, the surgeon will examine your shoulder to determine its range of motion without the pain factor. This test will help the surgeon plan the surgery, particularly if there are any tight tissues that need to be loosened.
The surgery could be performed using the Deltopectoral Approach or Anterior Superior Approach. The Deltopectoral Approach gives the surgeon a better view of the lower part of the shoulder socket, which is crucial because that’s where the socket’s foundation is going to be placed. This approach also allows the surgeon to protect important nerves and provides better access to the upper arm bone, which can be beneficial in complex procedures. However, some reports suggest that the risk of shoulder instability after surgery may be slightly higher with this approach. The choice between these approaches is made based on the surgeon’s experience and your specific needs.
In the Deltopectoral Approach, the surgeon will make a skin incision along the deltopectoral groove between two landmarks: the coracoid process and the upper end of the upper arm bone. Special care is needed to avoid damaging an important vein. The surgeon will then move and protect the conjoint tendon, a muscle that helps move the arm, to expose the subscapularis muscle. The subscapularis muscle is one of the rotator cuff muscles that can be split to reveal the shoulder joint.
The Anterior Superior Approach involves making an incision starting from the acromioclavicular joint, extending along the clavicle’s anterior border. This method provides direct access to the rotator cuff muscles, which are then prepared for the surgery.
After completing these initial steps, the surgeon will attempt to dislocate the humeral head (the ball part of the ball-and-socket joint of the shoulder). The preparation of the humerus (upper arm bone) and the glenoid (shoulder socket) for the prosthetics involves cleaning, shaping, and removing any bony outgrowths. The surgeon must place the prosthetics correctly, so they mirror your natural alignment.
The Glenoid Exposure process involves making sure that the socket is accessible and clear for the base plate. Sometimes if the glenoid has a bony defect, it may be necessary to add bone grafts or perform additional reaming. The preparation of the glenoid includes reaming and seating the base plate correctly. The base plate’s position is very important; it’s typically placed so that the foundation of the new socket tilts slightly downwards. The plate is affixed to bone with multiple screws.
Finally, a trial replacement cap or glenosphere is placed on the socket to check for fit and motion. This also allows the surgeon to select the appropriate size for the permanent prosthetic. Modern prosthetics offer different designs and sizes which ideally reduce impingement and provide a better range of movement.
Possible Complications of Reverse Shoulder Arthroplasty
After reverse shoulder replacement surgery (RTSA), there’s a risk that the new joint could get infected. This rate is usually between 1% and 10%. People with a health condition called rheumatoid arthritis or those who have had to redo the shoulder replacement are more likely to have this risk. If an infection happens within 3 weeks of the surgery, doctors can usually treat it by cleaning out the infected tissue, giving antibiotics, replacing part of the joint, and keeping the other parts in place. If the infection comes later, the doctors usually need to do one or two follow-up surgeries.
Another risk after this type of surgery is that the joint could become unstable or slip out of place, known as dislocation. This happens in about 3.6% of cases. There are several reasons why this might occur: the tissues around the joint might not be tight enough, there could be problems with the muscles of the shoulder, there might be damage to a nerve that runs through your armpit, part of your shoulder bone may be missing, the new joint might not be positioned correctly, or the new joint might be too small or too close to the middle of your body. This dislocation usually happens when the arm is stretched out, pulled in, and rotated inward. One method for this surgery, which goes through the front of your shoulder, has been linked with a higher rate of dislocation.
Sometimes, the nerve in your armpit (called the axillary nerve) may stop working for a while after this surgery. This can happen if the nerve is stretched too much while the surgeon is working on your shoulder.
Another issue during reverse shoulder replacement might be scapular notching. This is when the new shoulder joint rubs against a part of the shoulder blade, causing a small notch or cut. This happens very often when a certain type of shoulder replacement (named Grommet-style RTSA) is used. The doctors can lessen the risk of this by putting the new joint a bit lower in the shoulder.
There might also be issues with the base plate, which is a part of the new shoulder joint. This could happen if the base plate moves around too much or the bone doesn’t grow into the plate enough. To fix this issue, doctors have been improving the design of the new shoulder joint. For example, they’ve been using screws that can adjust their angles and a special screw in the middle that pushes the base plate into the shoulder and minimizes the plate’s movement. Another option is to tilt the base plate a bit downward and use locking screws, which has been proven to lower the amount of forces at the point where the base plate and the bone meet and lower the failure rate. But if these methods fail, the base plate needs to be replaced in a follow-up surgery.
Other less common complications include unexpected broken bones around the new joint during surgery, damage to blood vessels, abnormal bone growth around the joint, and issues with the surgical scar.
What Else Should I Know About Reverse Shoulder Arthroplasty?
Reverse Total Shoulder Arthroplasty (RTSA) is a surgery that’s becoming more and more popular worldwide. It’s used to treat a variety of shoulder problems in adults. In fact, over 60,000 such surgeries are performed every year in the USA, with patients generally finding their results satisfactory.
RTSA is mainly used for people whose rotator cuff isn’t working properly. The rotator cuff is a group of muscles and tendons that surround the shoulder joint, keeping the top of your upper arm bone firmly within the shallow socket of the shoulder. Sometimes, RTSA is also used for those who have a type of arthritis (joint inflammation) in their shoulder.
The way RTSA works is pretty clever. It changes the way your shoulder rotates, which makes it easier for a shoulder muscle (the deltoid muscle) to move your arm. This can help restore more normal shoulder motion and strength. In other words, it can help you get back to doing the things you love with less pain and more ease.
