Total Hip Infection

appears later than one month after the operation. The majority of the late infections develop months or even years after the operation. Many of the patients with late infections around the total hip joints were never completely pain-free. Occasionally they developed sinuses (draining holes) in their wound scars.

The classification is important because it has bearing on the outcome of the treatment of total hip infections. You have much better chances to get your total hip infection healed if the infection appeared early (within one month after the surgery).

When did the infection appear Per cent healed infections

Early 91 %

Late 70 %

2

The signs of an early infection

Basically, this is infection of the hematoma (collection of blood) that assembled in the wound after the total hip operation.

The patient runs high temperature and has severe pain from the operation wound. The operation wound painful, red, and swollen, occasionally with pus running from it. Because of such dramatic signs, the early infection is discovered and treated promptly, before the bacteria have had time to settle down and develop protective slime covering.

If a patient has wound drainage after total hip /knee arthroplasty, surgeon must take a sample (aspirate) from the depth of the wound to determine whether there is a deeper infection.

Treatment is always operative with reopening of the operation wound, evacuation of the infected hematoma, lavage (flush) of the wound with antibiotics, and massive antibiotic treatment. If the fixation of the total joint to the skeleton is good, the total joint is retained.

The blood coagula (the blood cake) that forms after total hip surgery is an excellent substrate for growth of bacteria. Bacteria who get foothold there are protected against action of antibiotics; antibiotics applied after operation cannot penetrate within these jelly-like black cakes.

If there is suspicion of incipient postoperative infection the surgeon must open the operation wound and carefully remove these blood cakes.

With quick treatment the majority of the early total hip infection will heal without further consequences for the total joint. (See the Table above).

3

The signs of a late infection of the total hip

The infection develops late, months or years after the patient left the hospital with the operation wound healed. This infection is basically caused by bacteria that colonized the surface of the total hip device at the operation and survived there under cover of slim envelope. A few of the late infections are, however, caused by bacteria that occured accidentaly in the blood. See the next chapter on acute haematogenous infections.

The patient notices increasing pain in the operated joint, the pain may be worse at night. In some patients there develops also a secretion from the operation wound site. Sanguineous or pus-like liquid comes from an opening (sinus) in the operation wound.

The blood tests show elevated parameters for ongoing infection and the temperature might be slightly elevated. In the minority of patients the late deep postoperative infection is so stealthy that even the infection parameters may be at the borderline to the normal. The surgeon may then believe that the patient suffers of aseptic loosening of the total hip. (Aseptic= without the presence of bacteria)

Because the late total hip infection develops so stealthily during the long time, the bacteria have had ample time to destroy the bone stock to which the artificial joint was once anchored. Therefore, the treatment of the late deep postoperative wound infection is difficult and the results are less predictable.

For more details of treatment of the infections around individual total joints see also the chapters

Treatment of total hip infections

Acute hematogenous infections

It is a special and rare form of the infection around the total joints. It occurs at once in a previously well functioning total hip joints, years after the operation. Occasionally, there is a source of infectious bacteria (skin boil, infected tooth, leg wound, e.g.) elsewhere in the body.

The bacteria from the remote infection traveled through the blood stream and get stuck on the surface of the total hip joint. There the bacteria are inaccessible to the body's defense system and may develop a rather widespread infection.

The total hip joints are most susceptible to this rare form of the joint infection during the first two postoperative years.

The treatment of this special infection form of infection usually follows the principles for treatment of the late infections.

If the infection has been discovered and treated early, the results of treatment of haematogenous total hip joint infections are equally good as treatment of early total hip joint infections.

How frequent are the infections around the total hip joint ?

The total hip infections are rare nowadays, only about 0,3 to 0,5% of the primary total hip joint operations develop infection. Moreover, the risk of total hip joint infection diminishes steadily as the surgeons are developing new methods for prevention of total joint infections.

Risk factors for development of hip joint infection are:

previous operation in the joint and previous infection in the operation area.

Other factors such as diabetes, obesity, rheumatoid arthritis, immune- suppressive treatment, although important, are less decisive.

Ongoing infection elsewhere in the body

What is NOT a postoperative wound infection

a redness of the skin around the operation wound without swelling or pain,

a slight swelling with blue discoloration of the skin around the operation wound

small areas of the operation wound that are black

a drop of clear fluid that appears around the stitches of an uneventfully healing operation wound

a positive bacterial culture from such liquid that shows growth of skin bacteria.

With proper care of the operation wound, changes of dressing and removal of stitches if necessary, these disturbances in the healing of the operative wound resolve themselves and they are nothing to worry about.

Collection of blood beneath the skin may occasionally become infected. This is a superficial postoperative wound infection.

The signs are pain, redness, swelling of the operative wound. This complication must be treated acutely (operative evacuation of the infected hematoma) and it usually heals without further complications.

In most patients with total hip replacement the superficial infection cannot propagate to the total hip joint if treated promptly. There is a strong fascial structure in the thigh that prohibits the propagation of the superficial infection into the depth and to the total hip joint.

Tests to diagnose total hip infection

(See the chapter: diagnosing the hip disease)

Blood tests:

ESR (erythrocyte sedimentation reaction) - elevated
CRP (C reactive protein) - elevated
WBC (white blood cells count) - elevated rarely

X-rays : generally there is destruction of skeleton around the infected total hip joint prosthesis. The surgeon accordingly suspects infection every time when the X-ray picture shows widespread destruction of the skeleton around the prosthesis. But there is no specific X-ray picture pinpointing to the infection around the total hip.

Other diagnostic methods to arrive at the diagnosis of infection around the total hip:

Gallium and Indium bone scans.

Gallium is supposed to accumulate at the site of bone infection. The isotope is ijected into the patient body and traced by a special camera.

Indium bone scan: you will yield a sample of your blood. In the laboratory the white blood cells will be separated from the blood and labelled with Indium radioisotope. Then the white cells will be injected back into your body. They will accumulate at and around the infected joint and detected by a special camera.

See also Diagnosis of hip disease

Puncture, aspiration, and bacteriological culture of the total hip joint - not much reliable methods if the infection is not well developed. The surgeon uses a long injection needle. Under guiding of X-rays the surgeon puts the needle into the total hip joint and aspirates (suctions) the joint fluid. The fluid is cultured for bacteria. Examination is done on the sterile operation room in anesthesia.

Direct microscopic examination of the tissues during the revision operation

Bacteriological culture from the tissues removed during the revision operation

The bacteriologists have developed also a very sensitive "molecular diagnostic method" to identify the presence of any bacteria in the operation wound. The method, the Polymerase Chain Reaction (PCR) can trace small amounts of bacterial genetic material (RNA). The disadvantage of this method is that it is hypersensitive producing false positive results. It may detect the presence of bacteria that are only contaminating the wound or the studied tissues, these bacteria are not causing any infection.

Recent method is Positron Emission Tomography (PET). Still in the experimental development. This method traces the accumulation of an isotope of blood sugar (glucose) in white cells. During infection the white cells consume large quantities of glucose. First reports indicate that this may be a reliable method to localize the infection around the prosthesis

Nothing grows from the sample taken from my total hip, but I still have an infection

Some bacteria are slow "growers".�

The main reasons why nothing grows from the samples taken from an obviously infected total hip, however, are:

bacteria in slime colonies on the surface of artificial joints are slow growers. To swab the surface of the removed total joint does not yield any bacteria - they are glued to the surface.

faulty bacteriological technique (anaerobe bacteria need special cultures)

treatment with antibiotics at the moment when the bacteriological sample was taken (all antibiotic treatment should be stopped for some days before taking of samples for bacterial cultures )

few samples taken ( at least seven samples should be sent for culture)

Because bacteria causing chronic total joint infections the microbiologists developed nev techniques for identification of bacteria causing chronic total joint infection. For more detailed information see the chapter Bacteria: Non Growth Identification.

PROPHYLAXIS AGAINST POSTOPERATIVE WOUND INFECTION

"With improvement of technology in clean air theatres, and availability in practice, slackness has crept into (operation) theatre protocol. "

Medhavan 1999

The absolute majority of the total hip infections is caused by bacteria that landed in the operation wound during the total hip joint surgery from the air. The surgeon, his operation team, and the patient are spreading these bacteria continually from the surfaces of their bodies into the air.

Operation room environment

Clothes

The source of all bacteria on an operation room are people working there AND the patient. The bacteria are produced on the body surface (mainly groin, inside of the thigh, and arm-pitts and travel on tiny skin scales in the air of the operation room. Every healthy person produces about 1000 such bacteria bearing skin scales per minute.

It is thus important to develop a clothing that would act as a barrier and prevent the skin scales from the people working on the operation room to escape into the operation room air.

So the surgeons (borrowing experience from atomic industry) developed impermeable, ventilated, astronaut-like gowns. The proper term is Body Exhausted Suits (BHS). The BES are made of hydrophobic materials, according to national and international standards. In spite of advertizing, these BES are uncomfortable, awkward to work in and expensive.

Thus other types of occlusive clothing have been produced from new materials, such as hydrophobic, non-woven, polyester pulp materials. The material is impermeable for bacteria, yet permeable for air

Several studies demonstrated that modern occlusive clothing is equally effective as body exhaust suits to diminish the counts of bacteria in the operation room air. Moreover, it is more agreable to work in and much cheaper.

Ventilation

Operation rooms are placed in the hospitals. The air on the hospital wards is dirty with hospital bacteria, sailing on the skin scales. If such ward air penetrates into the operation room, the dangerous hospital bacteria will settle into the operation wound.

Thus, the air pressure on the operation room must be slightly higher than the air pressure outside the operation room to push the air from the operation room. This is done by pumping large volumes of clean, filtered air into the operation room. This system is also called plenum ventilation.

On modern operation rooms, the whole air volume exchanges 16 to 20 times every hour. The bacteria sailing in the air are swept away, but new bacteria are steadily entering in the air. This is so because the fans produce an uneven stream of clean air with turbulence that mixes the "old" dirty air with the "new" clean air. Such modern plenum ventilation system produce air that contains about 50 to 150 bacteria / cu meter. Not much clean

So the surgeons constructed laminar air ventilation systems for the operation rooms. Such ventilation systems produce huge volumes of a very clean air so that the whole volume of the air in the operation room changes 300 -500 times per hour.

The allowed number of bacteria is maximally 10 bacteria / cu meter, in reality it is much lower (0,5 -1 bacteria/ cu meter). The clean air in both systemes is achieved by filtration with highly efficient filters (HEPA filters). These filters remove 99,75% of all particles large than 0,3 microns (1 micron = one thousand of millimetre). Bacteria are about 1 micron large, and skin scales with bacteria about 12 microns large.

The frequency of postoperative infections in patients operated on in these super-sterile operation rooms has been very low - less than 0,5 %.

The use of sterile operation rooms and astronaut -like operation gowns in itself cannot protect against postoperative infections if there are breaches in the strict operation room protocol.

Indeed, statistics demonstrate that total joint operations carried out on a plenum ventilated modern operation room with people there clad in modern occlusive clothings have equally low rates of postoperative joint infections as total joint operations done on super-sterile operation rooms with people clad in astronaut-like operation gowns. (Espehaug 1997)

prophylactic antibiotics.

In modern total joint surgery, practically all total joint operation patients, either operated on super-sterile or conventional modern operation rooms, will get prophylactic antibiotic.

Moreover, many patients will get prophylactic antibiotics in bone cement too . Studies demonstrated that these patients will have still lower rates of postoperative infections.

See more details in the chapter Prophylactic antibiotics

The rate of infections in individual hospitals

The rate of infections after total hip and knee operations varies among individual hospitals.

Small variations of these low rates of postoperative wound infections are caused by factors that are beyond the control of the surgeon. For example, if the hospital operates on many difficult cases, with long operation times, there would be higher rates of postoperative infection. If the rates of postoperative infections rise to the 1% level or above it, however, the surgeon should be concerned and make a close check-up of hygienic routines on the operation room.

Studies demonstrate that the rate of postoperative infections is higher after total hip operations done in hospitals with low operation volume be surgeons who carry out total hip replacement only seldom. (Katz 2001) (Available statistics confirm that this observation applies for total knees too.)

Annual volume of total hip operations Rate of deep infections

1 - 10 operations 0,4 %

26 - 50 operations 0,2 %

> 100 operations 0,1 %

The only way for you to know how many postoperative infections there have been in the hospital you choose for your operation is to ask directly. All hospitals should keep reliable statistics about the rates of postoperative infections occurring after the operations done on their operation rooms. As a collateral, you may ask about the annual volume of total joint operations.

For more facts visit also the chapters

bacteria causing infections around the total joints

treatment of infection with antibiotics

References:

Der Tavitian J et al.: J Bone Joint Surg-Br 2003; 85-B: 490 - 498

Espehaug B et al.: J Bone Joint Surg-Br 1997, 79-B: 590-5

Engesaeter LE et al.: Acta Orthop Scand 2003; 74: 644 -51

Katz et al J Bone Joint Surg-Am 2001: 83-A:1622 -29

Medhavan et al Deterioration of theatre discipline during total joint replacement. Ann R Coll Surg Engl 1999; 81: 262-5

Spangehl A. J Bone Joint Surg-Am, 1999;81-A:672-83

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