About Arthritis and Replacement
The most common symptom patients experience is pain in the shoulder at night. Other common symptoms include stiffness with limited range of motion, grinding or clicking in the joint with shoulder movement (called crepitus), and weakness from lack of use and pain.
Cause and Anatomy of Arthritis and Replacement
The shoulder joint is formed by an extension of the shoulder blade called the glenoid and the top of the arm bone called the humeral head. These bones form a ball-and-socket joint, which is the most mobile joint in the body. Wherever bones come together to form a joint, the ends of the bone are lined with a specialized tissue called cartilage. The cartilage is normally a few millimeters thick on each bone and creates a smooth gliding surface. The labrum is a structure that surrounds the glenoid. It deepens the socket and is a point of attachment for several ligaments that stabilize the shoulder. There are four muscles that attach the shoulder blade to the humeral head and are called the rotator cuff muscles. The two muscles in back are called the infraspinatus and teres minor, the top muscle is called the supraspinatus, and the muscle in front is called the subscapularis. These four muscles form a cuff of tissue around the humeral head and help keep the head centered on the socket.
Diagnosis of Shoulder Arthritis and Replacement
Shoulder arthritis is diagnosed with an X-ray. Dense structures like bone show up on the X-ray, but cartilage does not. The overall health and thickness of the cartilage is inferred by measuring the space between the main bones that make up the shoulder joint. When the cartilage thins and breaks down, the space between the bones gets narrower to the point where the bones touch each other. When bone rubs on bone, the bone reacts by becoming denser, which makes the bone appear more white (sclerotic). Often fluid from the joint gets driven into the pores of the bone and expands causing benign cysts in the bone that are also visible on the X-ray. In summary, the three hallmark signs of shoulder arthritis on X-rays are joint space narrowing, sclerosis of the bone, and subchondral cysts.
What Are My Options?
Physical therapy can help restore some range of motion, but is usually aimed at strengthening the muscles around the shoulder that become weak from lack of use. By strengthening the muscles around the shoulder, the pressure in the joint goes down, which helps alleviate pain. Aggressive stretching of the shoulder should be avoided because this can exacerbate the pain. A trained physical therapist will be able assess subtle muscular imbalances and can use different modalities such as massage, dry needling, and transcutaneous electrical stimulation to alleviate pain.
Anti-inflammatory pain medication and nonsteroidal anti-inflammatory drugs (NSAIDs) are considered a first line treatment for patients with arthritis. As the cartilage breaks down in the joint, proteins are released that create inflammation causing the cartilage to break down even more. NSAIDs help to block the effects of those proteins, which results in less inflammation and pain. These medications can be taken over the counter or by prescription. There are dozens of different NSAIDs, so often patients must try a couple different types to see, which one works best. NSAIDs can have detrimental effects when taken long term or over the recommended dose, such as kidney damage, ulcers, and even a small increased risk of heart attack or stroke. It is recommended that patients discuss use of these medications with their doctor.
The most common substance injected into the shoulder is steroid (often referred to as cortisone). Steroids are powerful anti-inflammatory medications, which turn off cellular signals that form inflammation. This results in reduced pain, but it usually takes 1-2 days for the steroid to take effect. Steroid injections result in 3 months of pain relief on average and can be repeated every 3 months without risk of any long-term detrimental effects. Patients should not have a steroid injection if they are considering a shoulder replacement within 3 months because studies have shown an increased risk of infection when steroid injections are performed within this period.
Platelet rich plasma (PRP) is an emerging technique for treating joint inflammation caused by arthritis with the body’s own healing factors. More and more studies are showing improved efficacy over steroid injections for treating joint arthritis. Blood is taken from a vein and spun in a centrifuge. This stratifies the blood into different layers. One of those layers is called platelet rich plasma, which contains healing factors called cytokines. The PRP is isolated and injected into the joint, which neutralizes the destructive enzymes in the joint and results in less inflammation and pain.
Hyaluronic acid is a substance that is naturally found in the joint fluid. It can be made synthetically or isolated from the chicken comb. When injected into the joint, hyaluronic acid treats inflammation in way that is different than steroid. It is currently only FDA approved for injection into the knee.
The primary surgical treatment for patients with shoulder arthritis is a shoulder replacement. This procedure involves making a 10 cm (4-5 inch) incision on the front of the shoulder. A natural muscular plane is developed between two muscles in the shoulder called the pectoralis and deltoid. One of the biceps tendons called the long head is released from its attachment in the joint and reattached to the upper humerus (upper arm bone). The front rotator cuff muscle (called the subscapularis) is released from its normal attachment on the humeral head. The humeral head and bone spurs are removed and a short stem with porous metal is inserted into the center of the humerus. The glenoid (socket of the shoulder) is exposed and the labrum removed. The glenoid is resurfaced with a piece of plastic that interdigitates with the bone. A metal ball is attached to the stem and the soft tissue balance and range of motion is assessed. The subscapularis muscle is reattached, and the skin is closed with multiple layers of sutures. It is critical that the subscapularis heal in order to regain pain free range of motion, which is why patients wear a sling and limit external rotation for 6 weeks after surgery.
Frequently Asked Questions
How do I know when it's time for a shoulder replacement?
You are considered a candidate for a shoulder replacement when you have pain every day that interferes with your ability to sleep and participate in daily activities and you have failed more conservative treatment with pain medication, activity modifications, and steroid injections. This surgery is performed under general anesthesia, so you should consult with your primary care provider if you are healthy enough to undergo this procedure.
Is there a cure for arthritis?
There is no “cure” for arthritis because at this point, we do not have the ability to replace the cartilage that normally covers the ends of the bone once it is gone. There are some data that stem cell injections may temporarily alleviate pain and can help prevent the further breakdown of cartilage, but they do not cause the cartilage to grow back. Because there is no cure, we have to manage the symptoms caused by the arthritis, which are pain and inflammation.
Why does my shoulder grind/pop?
When the cartilage lining the ends of the bone breaks down, it does not grow back. The underlying bone gets exposed, which then causes bone-on-bone articulation in the joint. Bone rubbing on bone creates the grinding in the shoulder. This creates friction and inflammation, which causes pain.
How do I know if I have shoulder arthritis?
Pain at night along with grinding/catching in the joint with shoulder movement are the most common symptoms of arthritis. If you are experiencing pain and inflammation that limits your activities, then you should make an appointment with your doctor. X-rays will be obtained, which is how arthritis is typically diagnosed.