The shoulder is the most mobile joint in the body. The shoulder joint is similar to a ball-and-socket joint that is comprised of three main bones: the collarbone (clavicle), the shoulder blade (scapula) and the upper arm bone (humerus), which extends from the shoulder blade to the elbow. The upper end of the humerus where it rotates is a smooth, rounded head (ball) that fits into the glenoid cavity (socket) of the shoulder blade. Because the ball is larger than the socket, it is more flexible, but has less inherent stability.
Muscles, tendons and connective tissue protect the shoulder joint and hold the various parts together. Because the shoulder joint is stabilized by muscles and tendons, rather than by bone, the shoulder has great flexibility. This gives the shoulder joint a wide range of motion enabling movements such as lifting, pushing and pulling.
However, this great degree of motion has a trade off; the stability of the shoulder is dependent upon the surrounding soft tissue and can result in a larger number of problems not faced by other joints supported by bony structures. A healthy shoulder can be damaged by disease or injury, resulting in severe pain, pseudoparalysis (false paralysis) and muscle weakness.
Pain is one of the key reasons people consider joint replacement surgery. Intense pain can also limit your range of motion and prohibit you from performing your normal day-to-day activities or getting a good night’s rest. Your doctor may recommend non-surgical treatments initially; however, if conservative treatment has failed to provide you any relief, surgical options may be considered.
How Does It Work?
The shoulder is the most mobile joint in the body. The shoulder joint is similar to a ball-and-socket joint but more closely resembles a golf ball on a tee. The rotator cuff provides the stability – keeping the golf ball on the tee.
The shoulder joint is comprised of three main bones: the collarbone (clavicle), the shoulder blade (scapula) and the upper arm bone (humerus). The glenoid (part of the scapula) and humeral head (part of the humerus) are normally the parts of the shoulder that have to be replaced because they rub together when you move your arm. In a healthy shoulder, these portions of bone are covered with cartilage, which allows for painless motion—lifting, pushing and pulling. But arthritis can damage this protective cartilage, which makes these motions painful.
Arthritis is one of the most common conditions that causes wear and tear to your joint cartilage and develops after years of constant motion and pressure on the joints. If non-surgical treatment options such as medication, physical therapy or lifestyle changes fail to provide relief, your surgeon may recommend shoulder replacement surgery.
Common Reasons for Shoulder Replacement
Osteoarthritis (degenerative arthritis), the most common form of arthritis, affects nearly 21 million people in the United States. It is a condition that causes “wear and tear” to your joint cartilage and develops after years of constant motion and pressure on the joints. As the cartilage continues to wear, the joint becomes inflamed and can result in unbearable pain and decreased range of motion. If non-surgical treatment options such as medication, physical therapy or lifestyle changes fail to provide relief, your surgeon may recommend a surgical treatment, including shoulder replacement.
Shoulder replacement surgery replaces the damaged part of your shoulder. Sometimes, only the ball is replaced. Other times, both the ball and socket are replaced. The ball is usually metal and the socket is usually plastic. During surgery, an incision is made in the front of the shoulder. Once your surgeon exposes your shoulder joint, the surgeon will remove the damaged bone and cartilage. The head of the humerus is then removed so your humeral shaft can be prepared for the insertion of the metal stem and ball.
In the case of a total shoulder arthroplasty, the socket (glenoid) portion of your shoulder will also be resurfaced and replaced to re-create the natural contours of the bones in a healthy shoulder. In cases where only the humeral head is replaced, a hemiarthroplasty is performed. Both are options for patients with painful and disabling shoulder joints.
Inflammatory (Rheumatoid) Arthritis
Inflammatory arthritis is a chronic joint disease that can attack any or all joints in the body. It can strike at any age and affects more women than men. In the shoulder, inflammatory arthritis causes the synovium to thicken and form a tissue growth (pannus) that clings to the protective cartilage and releases chemicals that attack and destroy it. The joint may become red and swollen, and pain may radiate into the neck and arm. Over time, the joint may become stiff and the muscles may weaken from lack of use. The bone also may be destroyed.
Shoulder replacement surgery is used for inflammatory arthritis sufferers to relieve severe arthritic pain and inflammation that does not respond to medication or physical therapy. Surgery can improve pain and mobility, and is typically done only after age 50 since artificial joints tend to wear down after 10 to 15 years.
Rotator Cuff Tear
Most people with a small cuff tear can be treated arthroscopically.
Surgery for rotator cuff tears usually occurs when a patient has a combination of shoulder arthritis and a massive irreparable rotator cuff tear. The rotator cuff is a group of muscles/tendons (supraspinatus, infraspinatus, teres minor and subscapularis) that surround the shoulder in order to keep the shoulder centered while performing shoulder-related tasks such as elevating and rotating the upper arm.
When a massive rotator cuff tear occurs, pre-operative evaluations usually reveal that the rotator cuff is irreparable or the muscles have atrophied to the point where they can no longer support the shoulder joint. The degenerated muscles lose their ability to keep the humerus centered on the glenoid, causing your arm bone to move upward and out of the socket. This impingement of bone on bone, combined with arthritis and previous shoulder injuries, can cause severe pain with pseudoparalysis (false paralysis) or stiffness of the shoulder.
Depending on the severity of the rotator cuff tear, your doctor may opt to perform a reverse shoulder replacement. In this procedure, the anatomy of the shoulder is reversed by attaching a metal ball to the shoulder bone and a plastic socket to the upper arm bone.
The upper arm can fracture for a variety of reasons. Proximal humerus fractures are typically caused by trauma-related injuries such as a fall, but become more common in persons around the average age of 60 as they become more prone to osteoporosis. The proximal humerus includes four parts: the articulating surface, the greater and lesser tuberosity, and the humeral shaft. When complex proximal humerus fractures occur, they tend to break off into three or four parts in consistent patterns around the ball-and-socket joint. Fractures are the most severe injuries to the upper humerus and can be difficult to treat.
Your surgeon may recommend that you do not have surgery, but instead participate in supervised therapy.
However, operative treatment is the most universal solution for these types of fractures that can be fixed. Depending on the age and severity of the fracture, your doctor may suggest shoulder replacement surgery. In this case, the ball and the upper portion of the humerus will be replaced in order to replicate the anatomy of the shoulder. The procedure usually helps regain shoulder function and reduces the amount of pain.
Avascular necrosis is a disease in which there is a temporary or permanent loss of blood supply to the bone. A number of conditions, including long-term use of steroids or alcohol, a traumatic injury, rheumatoid arthritis or unhealed fractures can cause the blood supply to the bone to be cut off. As the bone dies, it collapses. Although avascular necrosis can happen in any bone, it usually affects the ends of long bones such as the humerus. When this happens, the shoulder becomes painful and movement becomes limited.
The goal of treating avascular necrosis is to improve the use of the joint and to stop it from collapsing further. Treatment options will be based on your condition and may include medication, physical therapy or shoulder replacement surgery.
Primary Shoulder Replacement
Shoulder replacement surgery replaces the damaged part of your shoulder to recreate the natural contours of the bones in a healthy shoulder. Sometimes, only the ball is replaced (hemiarthroplasty), while other times, both the ball and socket are replaced (total shoulder arthroplasty). The ball is usually metal and the socket is usually plastic.
During surgery, an incision is made in the front of the shoulder. Once your surgeon exposes your shoulder joint, the surgeon will remove the damaged bone and cartilage. The head of the humerus is then removed and a metal stem is placed into the humeral canal. This provides a stabilizing anchor for the head.
Reverse Shoulder Replacement
If you have a massive, irreparable rotator cuff tear and arthritis, your surgeon may opt to perform a reverse shoulder replacement. The rotator cuff is a group of muscles and tendons that surround the shoulder in order to keep the humerus centered while performing shoulder-related tasks such as lifting the arm. When a rotator cuff tears, the muscles lose their ability to keep the humerus centered on the glenoid, causing your humerus to move upward and out of the socket. This instability, combined with arthritis or a previous shoulder injury, can cause severe pain and loss of function.
In this procedure, the anatomy of the shoulder is reversed by attaching a metal ball (glenosphere) to the glenoid and the plastic socket (humeral liner) to the upper humerus.
How Will It Feel?
The primary goal of the Equinoxe Shoulder System is to help you enjoy your daily activities with reduced pain and increased mobility. One of the main ways this is achieved is by ensuring a correct fit.
The Equinoxe allows your surgeon to choose from multiple humeral head heights, and an anatomically pear shaped glenoid design ensures a precise fit. A unique advantage of the Equinoxe is that any size humeral head can be paired with any size glenoid to best match your unique anatomy (Figure A).
If you are having a reverse shoulder replacement, the system will help restore pain-free shoulder function by empowering your deltoid to become the main functioning muscle in the absence of a healthy rotator cuff. The Equinoxe’s glenosphere is larger than most competing brands and helps maximize range of motion. The glenosphere also overhangs on the bottom of the glenoid, which minimizes impingement on the scapula and allows you to fully lower your arm to your side (Figure B).
The Equinoxe is designed to withstand long-term wear and tear from normal everyday activity. Only the highest quality materials are used to provide you the longest potential use of the implant.
The Equinoxe system is unique in that it features a platform stem that allows the surgeon to do either a primary shoulder replacement or a reverse with the same humeral stem. This design also conserves more of your bone because it does not require the surgeon to remove the original stem in the rare case a revision surgery becomes necessary.
The Equinoxe reverse is the only system that offers your surgeon an anatomic-shaped baseplate with six screw holes. This gives the surgeon multiple options to achieve solid bone fixation. Additionally, the bone cage can be filled with some of your own bone to promote bone growth, giving you and the surgeon the confidence of a secure long-term fit.
The Right Choice for You
Your surgeon will consider a wide variety of variables when selecting the shoulder implant that’s right for you. Your age, height, weight, lifestyle and your general health are among the most important factors. The Equinoxe Shoulder System is designed to accommodate these and other variations in anatomy to provide you with the best possible outcome.
After surgery you will receive pain medication and begin physical therapy. Depending on the procedure, you may be encouraged to use your arm soon after the surgery. You also may be asked to begin shoulder exercises to regain motion and strength. These exercises can be performed at home or on an outpatient-basis with supervised therapy. The specifics of your rehabilitation will be determined by your surgeon based on your condition.
Most patients are ready to go home between one to two days after surgery and may be asked to do shoulder exercises at home or with supervised therapy. You will be shown a variety of exercises designed to regain mobility and strength in your shoulder. It is important to follow the physical therapy protocol provided by your surgeon in order to facilitate the recovery process.
Exercise is crucial for proper rehabilitation. Therapy may begin the same day as your surgery and may continue up to four to six months post-op. Proper rehabilitation and willingness to follow all of your surgeon’s recommendations will contribute to a more successful recovery after surgery. Most patients are able to resume waist-level activities (writing) and possibly driving three to four weeks post-op depending on your surgeon and your condition. Activities such as golf, tennis and swimming can usually be resumed, but only after a thorough evaluation by your surgeon. Recovery time will vary for each patient.
Your surgeon will likely continue to evaluate your progress during the life of the prosthesis on a yearly basis. These evaluations may or may not require X-rays. It is important to see your surgeon if you notice any unusual changes regarding your new joint.