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The Shoulder Joint

Learn more about the anatomy and damage of a shoulder joint, the fixation of an artificial shoulder joint and what happens before the surgery.

Anatomy: How is the Shoulder Joint Structured?

The shoulder joint consists of the following bone structures:

  • the head of the humerus: spherical end of the humerus
  • the glenoid cavity: shallow concave surface on the shoulder blade
  • the acromioclavicular joint: connection to the clavicle

When in a healthy condition, both joint surfaces are covered with a layer of joint cartilage, that acts as a shock absorber, distributes and reduces the forces acting on the shoulder joint. The synovial fluid is a gel-like substance that lubricates the joint and enables a smooth movement of the joint and reduces friction. The shoulder is the most mobile joint in the human body, and is therefore referred to as a primarily muscle.

Illustration: Anatomy of the shoulder joint

Role of the Joint Capsule and Rotator Cuff

The shoulder joint is surrounded by a fixed joint capsule, which seals it off from the surrounding tissue. This produces ‘synovial fluid’, which enables the shoulder joint to move free from friction and also supplies the cartilage with nutrients.

Stability and Movement Thanks to Muscles

The spherical head of the humerus is only held very loosely in the small, shallow glenoid cavity of the shoulder blade. For this reason, muscles tendons and ligaments play an important role in stabilising the shoulder joint, while keeping it as mobile as possible. This is mainly achieved by a complex group of muscles known as the rotator cuff. This consists of four muscles which surround the shoulder joint like a cuff, protect it and enable the arm to move. Another important muscle here is the bicep. In addition to the muscles, tendons and ligaments also support the range of movement.

What Happens Before Surgery?

Patient Assessment – Your Personal Medical History

In the initial consultation the doctor will ask you about your complaints. They will ask where you have pain and where this pain radiates to. They will also enquire about the intensity of the pain, how long it lasts and any influencing factors which exacerbate or ease the pain.

Physical Examination – Where Does it Hurt?

The doctor will first examine your shoulders, neck, back and both arms and palpate the various structures. They will then conduct some movement tests to gain an impression of the mobility of the shoulder joint. They will also check the level of pain caused by various movements in the shoulder joint, such as adduction, abduction, rotating and raising.

X-ray – Focus on Your Shoulder

Using an X-ray image, the doctor is able to identify changes caused by shoulder arthrosis: i.e. owing to a loss of cartilage the intra-articular space between the humeral head and the glenoid cavity is either no longer uniform, is narrower or is even no longer visible. The bone structure of the humeral head and glenoid cavity appears irregular and altered; in very advanced stages the sections of the joint are deformed.

Preoperative Discussion – Your Chance to Ask any Questions

On the day before surgery, the surgeon will usually talk to you in detail about the planned procedure. During the consultation, they will explain the method of surgery and the type of prosthesis that will be used. Selecting the right prosthesis model depends on your individual bone condition, your body weight and your physical activity. The surgeon therefore normally decides beforehand which prosthesis model and type of fixation to use based on your X-ray and data.
In most cases, the surgeon will ask you about your state of health on the day before surgery. Do not hesitate to inform your doctor of any minor complaints you may have, such as colds and skin infections, even if you are not asked. Although harmless, these illnesses need to be cured before a surgical intervention.
The anaesthetist will also talk to you on the day before the surgery to explain the potential risks involved with the anaesthesia. They will also perform a few minor examinations, with a particular focus on heart and lung function and any possible allergies. They will then discuss the type of anaesthesia to be used.