ARTHROSIS

A joint (‘arthron’ in ancient Greek) consists of two bones (joint partners). These joint partners are covered with cartilage tissue, forming the joint, e.g., humeral head and glenoid cavity. The joint capsule is a protective sac that surrounds the joint and ensures that no synovial fluid leaks out and that the joint partners can slide smoothly against each other. Regular exercise keeps the cartilage tissue well ‘lubricated’ and provides nutrients to the joint.

If the cartilage is not well lubricated or subjected to too much stress, cracks can develop. At some point, the cartilage is worn away, and the bones rub against each other without protection. This can lead to an inflammatory reaction in the joint.

In common parlance, terms such as joint wear and tear or joint wear and tear are also used for osteoarthritis. Osteoarthritis is a progressive breakdown of cartilage tissue. It can be compared to the transmission in a car. If all the transmission parts interact smoothly with each other, there is no problem shifting gears. However, if there is sand in the transmission or if it is worn down through constant use, in the case of the joint, it would be, for example, abraded pieces of cartilage, then smooth movement can no longer take place.

In the shoulder, osteoarthritis can occur in different places. For example, the acromioclavicular joint, the glenohumeral joint, or the sternoclavicular joint (the joint between the sternum and the clavicle) can be affected.

Osteoarthritis is a normal process that develops over the years. For example, if you look at a new tire, it has a lot of tread at the beginning. Over time it gets thinner and smaller, and eventually, the whole tire is worn down, and in the worst case, you are driving on the rims. The body counteracts cartilage wear with bone compaction (sclerosis), cyst formation (fluid accumulation in the bone), and bone accretion (osteophyte formation). These are protective mechanisms of the body. Sclerosis begins due to increased pressure on the joint partners. The edges of the bone, in particular, become compacted and deformed to compensate for this pressure. The bone tries to distribute the force over a larger area so that it feels less pain.

An extreme example of this would be the fakir walking across the nail board.

If he were to step on only one nail, he would feel intense pain. On the other hand, if he steps on a board full of nails, the weight is evenly distributed over a larger area. The weight is evenly distributed over a larger area, and the pain sensation is automatically reduced.

The osteophytes or bone attachments that have developed are always a

clear sign of arthrosis. In X-rays, a joint space is always visible in healthy joints. This joint space results from the cartilage tissue, which is not visible in the X-ray.

Once the cartilage is worn away, this joint space also disappears. It gets narrower and narrower between the socket and the head, so to speak. This eliminated joint space is a sign of osteoarthritis. As the disease progresses, cartilaginous and bony structures can wear away and wear out. This can create ‘free’ joint space and, in turn, promote wear and tear. Wear can progress to the point where the position of individual bones in space (shoulder) changes significantly. The humeral head may dislocate posteriorly and cause increased wear in the posterior portion of the socket. In addition, if the rotator cuff is severely damaged, the humeral head cannot be adequately centered and supported in the joint. The humeral head no longer moves in its natural position, which forces asymmetric overloads in the joint. The glenoid cavity wears down on one side. If there is no longer any stabilization by the rotator cuff, the humeral head tends to slide upward toward the acromion. The humeral head chronically abuts the acromion. If the arm is moved in this position for a prolonged period, the humeral head rubs into the acromion. This phenomenon is also known as acetabulization (acetabulum = socket in the hip joint). The acromion becomes a ‘socket’, which is usually very painful for the individual. 

Osteoarthritis is most noticeable through pain. Often, affected persons describe the pain and a pulling sensation and pain associated with movement in the shoulder. Typical signs of osteoarthritis also include pain at night in a completely resting position.

After long periods of rest, symptoms such as stiffness and ‘starting pain’ are noticed. Pain occurs when the joint is loaded (the more the joint is loaded, the more it hurts). Sensitivity to weather and cold may indicate osteoarthritis. Swollen, thickened joints, inflammatory irritation, and noises during movement (rubbing, grinding) may also be noticeable symptoms. Bone attachments can lead to joint deformity, which can cause limitations in mobility. As a result, the joint loses its natural range of motion. Depending on whether the rotator cuff is also affected, strength may be impaired or reduced.

The X-ray is essential to examine the bone structures. With the help of this diagnostic procedure, joint space narrowing and the extent of sclerosis at the bone margin can be assessed. The X-ray provides the physician with information on whether cysts or typical bone attachments (osteophytes) are present and what the position of the joint partners is to each other. Here it can be seen whether the humerus is centered in the joint, whether it is displaced anteriorly or posteriorly, and whether there is still enough space between the acromion and the humeral head.

An ultrasound or MRI may be performed to assess the condition of the rotator cuff. The result of the ultrasound/MRI will determine what type of therapy will be used. For example, if the supraspinatus or subscapularis tendon is severely damaged, an anatomic joint replacement cannot be used. In this case, an inverted or inverse prosthesis is used. A CT scan is performed when it comes to preoperative planning. This imaging procedure creates an accurate 3D image of the shoulder joint. Here, the position of the glenoid cavity and the humeral head can be clearly seen. It is possible to see, for example, in which direction the glenoid cavity is rotated and how the humeral head is aligned. In addition, it can be determined here utilizing injections of contrast agents whether the rotator cuff is intact. The fatty nature of the rotator cuff muscles can also be assessed here.

Osteoarthritis is not curable per se. If osteoarthritis is diagnosed in the early stages, its progression can be slowed by various treatments. The painful joint needs a lot of exercise to maintain the nutrition of the remaining cartilage. The better the muscles are trained, the better the joint can be controlled, and thus less pain can be provoked. The choice of treatment interventions always depends on the stage of the osteoarthritis.

Physiotherapy and physical interventions can achieve functional improvement and pain reduction (cold/hot packs, ultrasound therapy, etc.). In the early stages, muscle strengthening and joint protection exercises often alleviate the symptoms of osteoarthritis.

Sometimes analgesic and anti-inflammatory drugs are also administered. The physician decides whether the use of cortisone injections into the joint is appropriate. In addition, there are alternative types of treatments, such as an injection of hyaluronic acid preparations (‘replacement’ of the synovial fluid) or the PRP (Platelet Rich Plasma) method, the injection of ‘autologous blood’ (the injection of the body’s own blood plasma into the joint). These interventions can help alleviate discomfort. Nevertheless, it is essential to know that this does not solve the problem. Worn cartilage tissue cannot be regenerated by the body or by the addition of drugs. Research has already succeeded in cultivating cartilage cells and using cartilage transplants in the knee area, in selected cases, to partially replace the damaged cartilage. A joint replacement (endoprosthetics) is the surgical solution for osteoarthritis. An artificial joint replaces the surfaces of the glenoid cavity and humeral head.

There are two types of artificial joints: the so-called anatomic/regular prosthesis and the reverse/inverse prosthesis.