Page 98 - ASOP ROT Study Guide

3 . 4 . 2 Specific complications

These may be further classified into early (soon after the operation) and late (months or years afterwards)
complications.

3 . 4 . 2 . 1 Specific early

Dislocation
In the immediate post-operative period the prosthesis will not be fully supported by the surrounding soft tissues.
The muscles and their proprioceptors may be temporarily out of action, through surgical trauma and pain
inhibition. A capsule of scar tissue will not yet have formed around the prosthesis. The hip in this period is at risk
from dislocation, particularly before the effects of anesthesia wears off. The risk of dislocation is reduced as
time passes but even years after, an injudicious move such as, in the case of the hip, twisting the leg into
extreme flexion with adduction and internal rotation may result in a painful dislocation. For this reason the
patient will need advice about dressing and may need aids to help in fitting stockings and may also benefit from
having a raised toilet seat.

Deep vein thrombosis
As stated above, the patient is at risk from deep vein thrombosis and therefore some sort of protection
(prophylaxis) is probably justified. The exact type of the prophylaxis is controversial. Blood clots may be
reduced in size and frequency by using drugs such as heparin which slightly inhibit clotting. The wearing of
support stockings is thought to help blood flow by preventing blood pooling in the legs as this effect is known to
increase clotting. It must be accepted however that this is by no means a clear cut issue and even if prophylaxis
is thought advisable, the best agent or technique is by no means universally agreed.

Infection
Infection is always a risk and this can be early or late. Many factors make an artificial joint prone to infection,
not only from recognized hospital bacteria such as staphylococcus aureus but also from organisms normally
regarded as natural inhabitants of the human body (commensals), such as staphylococcus albus, universally
found on the skin. It would appear that the presence of foreign material inhibits the body's ability to kill
bacteria. The reasons why this is so are not fully understood. Infection of a prosthesis is such a disaster,
that every effort must be made to avoid it. Techniques include antibiotic prophylaxis and the provision of an
ultra-clean air operating environment.

If all these precautions are taken then immediate infections should be eliminated and long term infections
reduced to less than 0.1%. Unfortunately in the United Kingdom, NHS resources do not always provide the ideal
operating environment and this figure is often exceeded, with rates of one to three percent being not
uncommon. Certainly anything greater than this is entirely unacceptable.

3 . 4 . 2 . 2 Specific late

Problems with joint replacement may occur as late as ten years after surgery or longer. The principal
problems are late infection, loosening and wear.

Infection
The causes of infection have already been discussed and it is probable that most cases of infection are caused
at the time of insertion of the prosthesis. Why they only become apparent later is not understood. It is also
suggested that infection may be blood borne as a consequence of contaminations of the blood stream
(bacteriaemias) commonly encountered in normal life. For example, there is circumstantial evidence that some
infections may follow tooth extraction which is known to cause significant bacteriaemias and is a cause of heart
valve infections.

Loosening and wear
Loosening to some degree is probably inevitable, from the simple passage of time, though the aim of surgical
technique is to delay this as long as possible. It is for this reason that we still need the alternative procedures
described above and why research must continue to find better materials and methods of prosthetic fixation.