Osteoarthritis of the shoulder (omarthrosis)

Cause | Symptoms & pain | Diagnosis | Conservative treatment methods | Surgical treatment methods

Osteoarthritis is defined as the degradation of the joint or joint cartilage. Because people are – thankfully – living longer and need to use their joints more and more, degradation events are also on the rise. These are widespread and well-known in the hips and knees, but the shoulder is also increasingly affected.

Joint cartilage is a fascinating tissue. It can withstand incredible pressure while maintaining a smooth, gliding surface and can also send intricate, precise signals about the position of a joint to the spinal cord. And all without its own blood supply. It is largely nourished by the joint fluid (synovial fluid) which is formed by the internal lining of the joint. The cartilage also ensures that the joint surfaces fit one another, i.e. are "congruent". It is important that a joint is moved so that the synovial fluid is well distributed and nourishes all regions within the joint.

HOW DOES OSTEOARTHRITIS OF THE SHOULDER DEVELOP?

In the beginning, the joint cartilage which forms the gliding surfaces for the joint components is overstressed, leading it to swell and soften. This makes it more susceptible to injuries and less resistant to stresses. If the stresses continue unhindered, this can lead to roughening of the cartilage surface. Osteoarthritis takes its course. The joint partners no longer glide without friction, which can lead to small tears in the cartilage. The joint reacts to this with inflammation, which can damage the cartilage even further. Fluid escapes from the joint (effusion) and it becomes painful. The layer of cartilage thins and is completely worn away at the most stressed sites. Pain increases and the mobility of the joint decreases. To reduce the pressure in the joint, the body attempts to enlarge the surface area of the joint: it forms bone spurs (osteophytes). These also disrupt movement in the joint. The osteoarthritis is now advanced.

As always with osteoarthritis, there can be many different causes. We differentiate between internal and external factors.

Internal factors

These include the genetic disposition partly responsible for the strength and resistance of the cartilage. However, there are also diseases that impact the cartilage, such as the chronic inflammation seen in rheumatoid arthritis. Also decisive are the growth phase and nutrition via the layer of cartilage and its composure.

External factors

If the rotator cuff is damaged, especially if the tendons at the head of your humerus are torn, the head of the humerus is no longer properly guided within the joint. The increased joint motion can lead to excessive wear. Over time, there is also decentralisation of the head of the humerus. This leads to asymmetrical stress in the joint which can degrade the socket on one side. This is called a cuff tear arthropathy. If the upper tendon of the rotator cuff is torn and retracts, it may be that the head of the humerus is rising within the joint and chronically abutting the acromion. This is painful and leads to a change in the joint anatomy. This is similar to what happens in the hip - acetabularisation occurs.

Osteoarthritis can develop following dislocation, particularly in the shoulder. If the head of the humerus is torn out of the joint, its cartilage grates on the anterior rim of the glenoid cavity (the joint socket). This has a very sharp edge, which alone can damage the cartilage. A (small) fracture to the bone of the head of the humerus can also occur during dislocation (a Hill-Sachs lesion). The glenoid cavity can also be affected as dislocation requires considerable force. The rim of the joint can be torn off (a Bankart lesion). The asymmetrical pressure alone can damage the cartilage on both sides.

Another cause of osteoarthritis can be overexertion, e.g. playing sport or at work. Overexertion can affect the rotator cuff or the joint directly. As seen above, stress influences the surface of the cartilage. When the stress increases beyond its capacity to regenerate, degradation occurs.

Accidents, especially bone fractures, affect not only the bones, but almost always the neighbouring joints as well. Depending on the way a force acts on the body or arm, it can be transmitted to the joint before the fracture occurs. The cartilage will be damaged. However, there are also fractures that traverse the joint and form a tier or groove. These frequently need to be operated on in an attempt to reconstruct the joint as far as possible. The results are not always perfect. Such fractures to the head of the humerus are difficult to treat well. The consequences of inadequate treatment can be devastating.

Orthopaedic surgeons especially fear joint infections. If a bacterium manages to penetrate the joint it can colonise and hide within the cartilage, which has no natural defence. The bacteria can multiply in peace until symptoms appear. And, as the joint space does not have a blood supply but is nourished through the synovial fluid, it is hard to reach with antibiotics. Such infections are therefore very difficult to treat and too often require surgery to cleanse the joint. Occasionally many times in a row. The cartilage usually sustains significant damage, threatening replacement of the joint with a prosthesis.

WHAT ARE THE VARIOUS SYMPTOMS CAUSED BY OSTEOARTHRITIS OF THE SHOULDER?

Most importantly: osteoarthritis is painful. It is certainly not equally painful for everyone, but the main symptom is clearly pain. These are typically shooting pains during movement, especially load-bearing. It is often not possible to localise the pain exactly: just somewhere in the shoulder. The pain occasionally radiates to the neck or arm. In advanced osteoarthritis these are sometimes joined by pain at rest. This resembles a dull burning sensation, a mild inflammation, but always there. Many patients also complain of nocturnal pains and can frequently no longer lie on the affected side. Because the affected arm is moved less, the scapula (shoulder blade) needs to work more. Its muscles are strained and begin to hurt. The tension typically moves into the neck. This becomes stiff and can lead to severe back pain or even headaches. Patients often feel the neck and back more than the shoulder.

The range of movement of the arm is usually no longer what it should be from an early stage. Movements above the head or on the back are difficult or very painful. Even pulling on a jacket can become an exercise. Later, raising the arm is more difficult in general. This is tiresome, not only when getting dressed. Brushing your hair and even eating can be difficult. Bodily hygiene is also impeded.

Cracking or clicking in the shoulder can be completely normal. A little fluid sloshes around or a shoulder joint clicks when raising the arm. Nothing unusual. Unless it hurts. However, in osteoarthritis the clicking is often associated with pain. This is a sign that the cartilage is no longer gliding smoothly, but jerking.

The swelling is often not recognised as the shoulder is surrounded by thick musculature. Nonetheless, it contributes to the restriction of movement. When the arm can no longer be moved well, the blood circulates less well, causing it to swell. Reddening in the shoulder is also rarely noticed because the skin does not lie directly over the joint. The large coat of muscle screens the reddening.

Every time there is something wrong with the shoulder, this is transmitted to the bursa. This is located between the acromion and supraspinatus tendon and acts to ensure the tendon does not chafe against the acromion. In osteoarthritis, however, it is often inflamed and also causes pain such as a steady burning sensation beneath the acromion. This pain is usually not perceived in isolation.

Joints want to move. If this does not happen – or happens too little – such as in osteoarthritis, it may be that the surrounding soft tissues overall and the joint capsule in particular have started to shrink. The joint becomes stiff. This accelerates the progression of the osteoarthritis. The "start-up" difficulties in the morning can no longer be overcome and the joint is barely moved throughout the day. This makes it even stiffer.

HOW IS OSTEOARTHRITIS OF THE SHOULDER IDENTIFIED AND EXAMINED?

The most frequent symptoms reported by patients are pain and restricted function of the arm. However, because many other problems cause these same symptoms it is very important to ask precisely when which symptoms occur, when and how they begin and any other symptoms the patient may have. It is also important to know the general circumstances. The doctor will then examine you. They will try to find out what is causing your symptoms and exclude other causes. The examination always includes active and passive movement of the joint and the function of the rotator cuff. Strength is usually also measured. The doctor will perform further tests (such as for the biceps tendon) as required. Questions about your medical history (anamnesis) and the examination together lead to the correct diagnosis in approx. 80% of cases. Although the diagnosis can usually be made on the basis of the anamnesis and clinical examination, further examinations will be required. Not only to confirm the diagnosis, but also to determine the extent of the osteoarthritis and to be able to exclude other problems. Precise planning is needed in the event of surgery, requiring further examinations.

X-rays

These are quick, cheap and highly informative regarding the bones, joint and osteoarthritis. They are therefore almost the standard for shoulder examinations. The exposure to radiation from a single X-ray image is extremely low, roughly the same as for a flight to the USA.

MRI (magnetic resonance imaging)

MRI is a procedure that generates a series of images using the hydrogen protons (i.e. water content) in the tissue as the imaging basis. An image series means that it (virtually) dissects the part of the body to be examined into several millimetre-thick slices. This provides insight into a three-dimensional body. MRI is less suitable for bones as they contain little water. However, it is perfect for the soft tissues. These can be imaged to a high degree of accuracy, illustrating even the slightest damage. This works best when a small amount of contrast medium is injected into the shoulder joint beforehand. And the best thing is that there is no exposure to radiation. This is the most important diagnostic method for the shoulder. For example: in osteoarthritis it can show whether the rotator cuff is still intact or not.

Computed tomography (CT)

This also takes a series of image slices, but on the basis of X-rays. It is essential for making a three-dimensional reconstruction of a bone or its damage. It is therefore often used for planning the implantation of a prosthesis. As the soft tissues are imaged less well than with MRI, it is used less often in the shoulder. The exposure to radiation is considerably greater than for a single X-ray image, but still well below a dangerous level.

Ultrasound

Ultrasound is a technique learned from bats. A Piezo electrode sends an (ultra-) sonic signal into the tissue and records its echo. This functions excellently for soft tissues, but the soundwaves do not pass through bones. Its use therefore has limitations for the shoulder. However, it is quick and simple to prepare and is the only method with the advantage that it can take "films" in real time. This benefit is priceless for certain situations. Furthermore, the patient need not lie in a narrow tube, which can be decisive for certain patients. Ultrasound is rarely used in osteoarthritis.

WHAT THERAPIES ARE AVAILABLE FOR OSTEOARTHRITIS?

The forms of osteoarthritis are as varied as the treatment options. These generally depend on the severity of the osteoarthritis and the patient’s symptoms.

Conservative treatment methods

Wherever possible, an attempt is made to achieve relief of the symptoms without surgery (conservatively). This is primarily in the early stage of osteoarthritis where the function is still well maintained but the pain is becoming noticeable.

Mild pain relievers such as Dafalgan (paracetamol) are well tolerated and have few side effects. They are often used as an initial therapy. The somewhat stronger non-steroidal anti-inflammatory drugs (NSAIDs) help to reduce inflammation, for which they are mostly used. Moreover, they act where the pain arises and are therefore particularly suitable for use in the movement apparatus. Strong pain relievers such as tramadol or opiates are only used when there is no other solution for chronic pain. They are liable to habituation (unlike the others above), which means that a person tends to use more of them over time. They are well-known to be addictive if taken for a long time. Pain-relieving ointments are not used often for the shoulder as they are largely unable to penetrate into the joint. The large deltoid muscle is in the way.

Cortisone is not actually a pain reliever but a hormone, a corticosteroid. The above pain-relievers are therefore demarcated from this as "non-steroidal…". Cortisone modulates the body’s immune response and prevents inflammatory reactions. It is a very potent pain reliever in this way. When taken as a tablet it also has known side effects such as water retention, weight gain, etc. It is often essential in rheumatic disorders and the positive effect is much greater than the side effects. It should only be used as a tablet for osteoarthritis if there is no other option and the application is kept brief.

This relieves pain excellently and cooling of a painful joint is often the best idea. The ice must not come into direct contact with the skin as this could cause damage. It is better to place the ice or cold-pack in a plastic bag, then place this in a kitchen towel. The shoulder joint is surrounded by the large and powerful deltoid muscle, hence the cold unfortunately often cannot reach into the joint.

Physiotherapy is often one of the shoulder specialist’s most important partners. It is nearly always used in one form or another. In osteoarthritis it can have an analgesic effect, i.e. relieves pain, but also keeps the joint mobile. It employs physical methods such as heat, cold, massage, needling or electricity as well as therapeutic exercise. The exercise is essential for maintaining mobility and musculature as well as for proprioception. The physical measures not only address the pain, but relieve the hardened muscles.

These are a further useful measure for addressing pain. Under guidance from X-rays or ultrasound, a mixture of cortisone and local anaesthetic is injected into the joint. The local anaesthetic acts immediately; the cortisone is long-term. As the cortisone is not taken as a tablet, where it would be distributed throughout the body, but injected locally into the joint cavity, it does not have the side effects of the tablet. Patients are occasionally themselves astonished at how well such infiltrations work. An arm that has hung painfully by the body for weeks can suddenly be lifted again - without pain! As each infiltration has a (very small) risk of infection and as cortisone can damage intact cartilage or tendons, infiltrations are only performed in the event of advanced osteoarthritis or if the patient can no longer withstand the pain.
And, as cortisone does not heal but "only" relieves the pain, the effect is not permanent. It is therefore sensible to perform physiotherapy after the infiltration so that the effect lasts longer.

Surgical treatment methods

Surgery must be taken into consideration if the above conservative treatment methods are exhausted or the restrictions are too great.

Arthroscopy of the shoulder is an excellent operation that is non-invasive and can solve or improve many shoulder problems, but not osteoarthritis. There have been repeated attempts to relieve the symptoms of osteoarthritis by cleansing the joint during arthroscopy (debridement). However, the results have been minimal and short-lived, hence the effort and risk of surgery is not worthwhile.

The only good, permanent solution for advanced osteoarthritis is joint replacement, a prosthesis. Incredible advances have been made in prostheses, especially for the shoulder. Given the correct indication and surgery, they restore mobility and relieve pain.
In principle, there are two types of prostheses for the shoulder (in many different formats).

• Anatomic prosthesis: This copies the human anatomy but of course replaces the destroyed joint parts. Not though the muscles, which are responsible for smooth motion. It therefore consists firstly of a socket, usually made of specially processed polyethylene, which is cemented into the existing glenoid cavity. Secondly there is a humeral head, usually made of cobalt chrome and titanium, which has its own shaft inserted into the shaft of the humerus. This prosthesis can however only function if the musculature, especially the rotator cuff, is fully intact and functional. This is rarely the case in osteoarthritis.
• Inverse prosthesis: This is a joint care show-piece and a remarkable invention. This is because it not only recreates the anatomy of the joint, but its function as well. It does this by inverting the joint components. What was previously the socket is replaced by a half-sphere. It fits its counterpart, the socket, precisely, but it is implanted onto the head of the humerus. As this socket is deep and has a smaller diameter than the original head of the humerus, the system has such initial stability that it can sometimes even manage without the rotator cuff. This is essential for osteoarthritis of the shoulder. The smaller diameter does decrease the range of motion slightly, but it is certainly better than before the surgery. Freedom from pain is more or less guaranteed.

These new implants are a great success; you will be able to use your arm without pain after only 1-2 months. As the prostheses are constantly being adapted to the latest scientific knowledge, there is little information regarding their durability. However, all recent studies have shown a durability rate of more than 90% after 10 years.

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