INFECTED TKR

Abstract

Despite of improved operative technique, ultra-clean air in the operating theater and systemically administered as well as in bone cement loaded antibiotics, septic complications after replacement arthroplasty of the knee still exist. Depending of the follow-up time in different reported series insidence vary from 0.5 to 5 per cent.

Classic clinical symptoms, painful, swollen knee joint, possibly fever, indicate to more accurate examinations.

Lesson to learn: No treatment before adequate diagnosis ! No “homeostatic” antibiotics before accurate examinations. If the very first contact with physician or surgeon happens in such conditions, that adequate diagnostic methods are not available, patient has to be referred to hospital or institution with capable facilities.

Prosthetic infection can be classified in many ways. The following classification is useful for the treatment purposes.

Classification of infection:

1. Early postoperative infection less than 4 weeks after surgery.

1. superficial

2. deep

3. extensive soft tissue defects due to skin necrosis

2. Originally patient is operated for aseptic loosening, but intraoperative cultures are positive.

3. Late chronic infection

4. Acute hematogenous infection

Diagnostic methods:

1. Clinical examination:

• - symptoms can be suppressed by painkillers or immunomodulant drugs

• - wound healing problems

• - sinuses

• - swelling, redness

• - pain

• - temperature increased

2. Blood chemistry:

ESR, C-reactive protein and blood white cell count/ differentiation are helpful.

Be ware if the patient has such a general disease, which increases fex CRP

3. Routine x-rays. In early cases no significant signs, in late cases might appear erosions or cysts.

4. Isotope scintigraphy. Technetium- or indium labeled leucosytes are given intravenously

The patient is scanned 24 hours. Extended scintigraphy seems to be more sensitive than routine 6 to 8 hours‘ scintigraphy.

5. Joint aspiration.

One has to sure, that the patient is not on antibiotics. If she/he is, antibiotics has to be stopped for two to four weeks, and aspiration performed after that, unless infection is not clinically obvious or situation is not life-threatening

White cell count/differentiation can be for some help. When the cell count is less than 2000/ml, and majority of cells are mononuclear, the result is indicative negative for infection. White cell count over 10000/ml, and majority polymorphonuclear, speaks for infection.

When the aspiration has been carried in aseptic condition, positive culture is strong evidence for infection.

Adequate handling of sample is important: as little as possible air in the syringe and as short as possible time used for transportation to lab.

Treatment protocols

Treatment protocols can rather straight forward: if any sample culture is positive,

Two-stage revision arthroplasty is carried out. But also more conservative opinions are reported.

1.a. Early postoperative, superficial infection:

Surgical débridement of the wound.

Careful examination of retinaculum layer. Lavage and wound closure if possible. Systemic antibiotics. Joint puncture and aspiration through healthy skin area, never through open wound.

b. Early postoperative, deep infection:

Open débridement and careful lavage with retention of prosthesis. Additional peroperative samples for culture in order to confirm earlier pathogene definition.

Systemic antibiotics regarding sensitivity estimation. Arthroscopic debridement and lavage has not proved to be better or neither as good as open. New aspiration 4–6 days after. If white cell count clearly over 10000/ml and possibly culture positive, new debridement and lavage. If third debridement comes necessary, even without bony changes, removal of prosthesis and antibiotics- loaded spacer has to be considered.

c. Dehiscense of wound or soft tissue defect due to the necrosis:

Wound débridenent, antibiotics and depending on the extend of defect either partial closure, skin grafting or pedicled gastrocnemius muscle flap is performed.

2. In some cases there is no signs of infection, and the is operated as an aseptic loosening. In all revision, routineously 4 to 5 tissue samples should be taken for culture. If preoperatively there is any doubts about infection, histological examination of frozen sections should be carried out. If there are high count of polymorphonuclear cells, results of culture has to be waited. If later on in minimum two samples same pathogen is growing, the case has to be considered as infected. Two-stage revision protocol is recommended.

One positive sample cannot be regarded as a concluding proof. Long term antibiotics is recommended.

3. Late chronic infection has insidious , slowly progressing onset. Symptoms can be confusing mild, and can lead to misdiagnosis. Method of choice is débridement, removal of the prosthesis and all bone cement, and placement of an antibiotics-loaded cement spacer. No dead space is left , but has to be filled with antibiotic-loaded collagen or antibiotic-cement beads. The patient is put on systemic antibiotics, preferably combination of two. Antibiotic therapy is continued six- to eight weeks. Healing process is controlled with ESR and CRP tests. If the blood test normal and clinical situation is normal, delayed revision arthroplasty is performed. Antibiotic loaded-cement is always used.

4. Acute hematogenous infection. Onset is usually acute and symptoms dramatic.

Sometimes distant focus can be found. If the history is rather short( less than 14 days) open débridement, retainment of prosthesis, antibiotics-loaded collagen filling of the joint as well systemic antibiotics is recommended. Recovering is monitored by blood chemistry and repeated joint aspiration and cultures. If in aspiration sample there is high polymorphonueclear count and culture possibly positive, new débridemand is carried out. If signs of infection still continue, two-stage exchange to be considered.

Pathogenes

Gram-positive

staphylococci are most frequent patogene in total knee replacement infections (95%).

Gram-negative

bacilli cover the rest (5%). Coagulase-negative staphylococci has grown up the most important bacteria, and it‘s resistance against antibiotics has turned frightening.

Spacers

In cases with short history retainment of prosthesis can be considered. Many authors change of polyethylene bearing.

In two-stage revisions static antibiotic-loaded cement spacer was used during

The six to eight weeks‘ interval. Static spacer is connected with extensive bone loss as well as stiff causing problems in secondary revision. Molded cement spacer is used in order to avoid complications and to achieve better functional results.

Failure

In some cases treatment of infection is unsuccessful. Arthodesis with method of Ilizarov or intramedullary nail or sometimes above-knee amputation comes necessary.