The shoulder cap prosthesis | The shoulder prosthesis

The shoulder cap prosthesis

A shoulder cap prosthesis is an artificial surface replacement that is used to replace a destroyed humeral head. It is (usually) a metal cap that is applied to the ball of the humeral head to cover cartilage or bone abrasion. It is also known as a hemiprosthesis or hemiarthroplasty, since, unlike a full shoulder prosthesis, the head of humerus and the socket do not also have to be replaced.

A shoulder cap prosthesis can be anchored using bone cement, but cementless surgical techniques are also possible. A shoulder cap prosthesis is mainly used in cases where a shoulder cap prosthesis serves as a replacement from the surface of the head of humerus.

  • Rheumatic diseases of the shoulder joint (rheumatic shoulder)
  • Necrosis of the humerus (humeral head necrosis) or
  • Shoulder wear (omarthrosis).

The implantation of a shoulder cap prosthesis can usually achieve a good reduction in pain.

The extent of movement of the shoulder can be increased compared to the state before the operation by means of targeted follow-up treatment. However, if the shoulder joint is already stiffened before the implantation of a shoulder cap prosthesis, the operation cannot lead to restoration of mobility. Shoulder cap prostheses are either used in combination with a glenoid socket replacement or (in most cases) without an artificial glenoid socket.

The glenohumeral joint is opened either via an anterior or an upper access (reaching the glenohumeral joint is as muscle-sparing as possible) and the humeral head bone is exposed. A wire is then placed centrally and the appropriate prosthesis size of the glenoid cap is selected. A millimeter-wide layer of the worn surface of the humerus is removed with a special milling machine so that the implant can be placed.

If necessary, an additional joint socket is implanted. The shoulder cap prosthesis is now inserted either with bone cement or cementless by means of a press fit and then the humeral head with the prosthesis is re-inserted into the glenoid cavity.This is followed by a detailed examination of the running behaviour of the shoulder cap prosthesis in the glenoid cavity and the stability of the shoulder. The surgical wound is sutured again and a shoulder splint is applied.

In general, the rate of complications caused by the installation of shoulder cap prostheses is low. The general risks apply as for any operation: there is also the risk that the prosthesis could dislocate (luxate).

  • Thrombosis
  • Embolism
  • Bleeding
  • Infection
  • Vascular or nerve damage
  • Wound healing disorders

Advantages In contrast to a complete artificial shoulder joint replacement, only a very small part of the humeral head has to be removed in a shoulder cap prosthesis.

As a rule, only the surface of the humeral head is pre-milled, which spares healthy bone. The humerus does not have to be opened in the case of a shoulder cap prosthesis, since the prosthesis does not have a stem that has to be inserted into the humeral shaft. A further advantage of the shoulder cap prosthesis is the small surgical accesses.

Under certain circumstances, the prosthesis is only fitted using minimally invasive surgical techniques (“keyhole surgery”). In addition, if the shoulder cap prosthesis loosens, a completely artificial shoulder joint can still be used after years. 2 Disadvantages However, a shoulder cap prosthesis requires a sufficiently large contact surface.

This means that the damage to the humeral head must not yet be too great for a shoulder cap prosthesis to be installed. In individual cases, this can only be determined during the operation, which is why the patient must then switch to another, more suitable shoulder prosthesis. Speak against the installation of a shoulder cap prosthesis:

  • Bacterial Infections
  • Paralysis or damage to the shoulder muscles (rotator cuff)
  • Osteoporosis
  • Bone instability and
  • Bone death (osteonecrosis)

Immediate loading of the new shoulder joint is generally possible.

During the one-week stay in hospital after the shoulder cap prosthesis has been fitted, the shoulder is usually cooled, the wound checked and painkillers administered. The stitches can be removed after 10 to 12 days. A shoulder splint should be worn for about 6 weeks.

During this time the passive mobility of the shoulder should be practiced with the help of physiotherapy. After removal of the shoulder splint, active exercises can be performed with the shoulder. Sports that strain the shoulder (such as soccer, handball, downhill skiing or tennis) are unfavorable for the time after the shoulder cap prosthesis has been inserted.