Infection following total knee joint arthroplasty: considerartions and treatment

Abstracts

As artroplastias totais de joelho apresentaram nas últimas décadas apreciável melhora em relação aos resultados cirúrgicos devido à difusão de técnicas operatórias precisas e ao desenvolvimento de materiais de implante de alta tecnologia. Apesar disso ainda estão sujeitas a complicações, sendo a infecção a mais difícil de ser solucionada. Neste artigo discutimos os fatores de risco para infecção, classificação, condições clínicas e cirúrgicas, assim como métodos diagnósticos. As opções de tratamento incluem supressão com antibióticos, manutenção da prótese, troca imediata ou em dois tempos dos componentes protéticos e os procedimentos de salvação. Além disto, os autores apresentam o protocolo de tratamento utilizado no Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da FMUSP pelo Grupo de Artroplastias.

Artroplastia do Joelho; Infecção; Fatores de risco

REVIEW ARTICLE

Infection following total knee joint arthroplasty: considerartions and treatment

Ana Lúcia Lei Munhoz Lima^I; José Ricardo Pécora^II; Roberto Motta Albuquerque^II; Adriana Pereira de Paula^III; Caio Oliveira D'Elia^IV; Alexandre Leme Godoy dos Santos^IV; Alberto Tesconi Croci^V

^ICommunicable Disease Specialist, Chief of Infection Service of the IOT-FMUSP

^IIOrthopaedist, Assistant physician of the Arthroplasty Group IOT-FMUSP

^IIINurse of the Commission of Hospital Infection Control of IOT-FMUSP

^IVResident physicians IOT-FMUSP

^VFull Professor, Chief of the Arthroplasty Group IOT-FMUSP

^{Correspondence}

SUMMARY

Total knee arthroplasty results have markedly improved during the last decades due to diffusion of accurate surgical techniques and development of high-technology implant materials. However, complications still develop, infection being that of most difficult resolution.

Risk factors for infection, classification of infections, clinical and surgical conditions, as well as diagnostic methods are discussed in the present article. Therapeutic options include suppression by antibiotic therapy, maintenance of the prosthesis, immediate or two-step replacement of prosthetic, and salvage procedures. In addition, the authors describe the treatment protocol used by the Arthroplasty Group in the Institute of Orthopedics and Traumatology (I.O.T.) of the Clinics Hospital of the Medical School of the São Paulo University.

Keywords: Arthroplasty,Replacement, Knee; Infection, Risk Factors

INTRODUCTION

The conception of replacement of the knee joint surface as a treatment for severe knee joint diseases has drawn the attention since the XIX century. In 1860 Verneuil⁽¹⁵⁾ suggested the insertion of soft tissue for knee joint reconstruction. However, at the beginning of the past century the knee joint arthroplasty (KJA) greatly developed due to the development of adequate implant materials, such as metallic and acrylic alloys, and the improvement of the surgical technique, mainly stimulated by Campbell⁽¹⁾, MacIntosh⁽¹⁰⁾ e McKeever ⁽¹¹⁾.

There are high-technology knee prostheses of different designs available today. With increased life expectancy worldwide and more accurate diagnoses, the use of such prostheses has led to increased indication and survival.

The main objectives of knee joint arthroplasty are pain relief, functional gain achievement, and deformity repair. It is mainly indicated in osteoarthroses, rheumatic and hematologic diseases, and osteonecroses⁽⁶⁾.

KJA consists of joint replacement in their femoral, tibial, and patellar segments with prosthetic implants, made of a metal femoral component, a tibial component made of a metallic base supporting a polyethylene base, and a patellar component made of polyethylene only.

KJA is a great surgery and several postoperative complications may develop, including infection, the most severe and feared complication. Infection in KJA is a challenge because treatment is difficult and often time-consuming⁽⁶⁾.

Incidence

National data of KJA infection are not available.

International literature reports an incidence of 1%-5%. In excellence centers with specialized staff and great volume of KJA, this rate amounts to less than 1%.

Economic impact of infected KJA treatment amounts to US$ 300 million per year in the United States ⁽¹³⁾.

In the Institute of Orthopedics and Traumatology (I.O.T.) of the Medical School of the São Paulo University, the incidence of KJA infection has been stable for the last three years, amounting to approximately 3% ⁽⁹⁾.

Etiology:

Post-TKA infections can develop through three mechanisms: direct implant of bacteria; hematogenic route; reactivation of quiescent foci.

Direct implant during surgery results from an inadequate surgical environment, faulty sterilization technique, and prolonged surgical duration.

Hematogenic contamination generally stems from distant foci, such as urinary tract or pulmonary infections, infected skin ulcers, and odontogenic abscesses.

Another infection route is the reactivation of osteoarticular quiescent foci, such as pyoarthritides, osteomyelitis, or previous surgical manipulations.

Microorganisms causing joint infections following total knee joint arthroplasty include Gram-positive bacteria in 50% to 60% of cases, Gram-negative bacteria in 10% to 20%, and mixed in 10% to 20%. In most cases, aerobic bacteria are involved⁽⁴⁾.

Tables 1 and 2 show the most prevalent bacteria worldwide⁽¹⁴⁾ and in the I.O.T.⁽⁸⁾, respectively.

Less frequent pathogenic microorganisms include fungi, mainly Candida sp, and the tuberculosis bacillus.

Risk Factors for Infection

The risk for infection in KJA is related to host's condition, surgical environment, and the surgical intervention itself.

As for the host, some systemic diseases, lifestyle, and clinical conditions (Table 3) contribute to increasing the risk for infection in KJA.

As for surgical environment, measures are of paramount importance to prevent infections following KJA, such as maintenance of the air-conditioning system, use of laminar airflow, sterilization, and appropriate prosthetic material packaging, as well as antisepsis technique, appropriate use of drapes, and appropriate adornment of the surgical staff.

The surgical procedure itself contributes to increasing the risk for infection, when the technique is inappropriate, surgical duration is long, manipulation of soft tissue is excessive, and there is a great number of persons in the operative field. .

Diagnosis:

Pain is an important symptom and found in almost all patients with infection following KJA.

Clinical examination of the knee may show increased volume, increased local temperature, edema, joint effusion, hyperemia, fistula, and skin necrosis. Movement range may be decreased.

Joint stability and neurovascular examination of the legs are not affected in most patients.

Rehabilitation course is clearly preserved.

Blood tests useful for diagnosis include white blood cell count (including differential count), erythrocyte rate sedimentation, C-reactive protein, and acid a-glycoprotein. Although these tests are not specific, abnormal results corroborate the diagnosis of infection.

Fluid aspiration allows one to obtain synovial fluid to confirm diagnosis. Gram staining and culture for aerobic and anaerobic bacteria are used to evaluate synovi)112 fluid and has high rates of sensitivity, specificity, and accuracy⁽¹²⁾.

In some cases where infection is presumed and diagnosis is not confirmed, arthroscopic biopsy of synovial tissue is indicated for histopathological and bacteriological analysis⁽⁷⁾.

As for imaging testing, plain radiographs can show prosthesis release and bone involvement while ultrasonography can demonstrate periarticular or intraarticular collection. When clinical picture and joint aspiration are not conclusive, scanning with technetium-labelled white blood cells can be definitive since it has high sensitivity and specificity for osteoarticular infections.

The authors recommend the following protocol for diagnosis of infection following KJA: history and physical examination, white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and acid a-glycoprotein, joint aspiration, and plain radiographs of the knee joint (anteroposterior and lateral incidences). In addition, scintigraphy with Tc-labelled white blood cells and arthroscopic biopsy of synovial tissue may be carried out in difficult cases.

Classification:

The Center for Diseases Control and Prevention – U.S.A.(C.D.C.) classifies infections following total knee joint arthroplasty according to their localization (superficial or deep) and duration (acute and chronic)⁽²⁾.

Superficial infections are those affecting soft tissues over muscular fascia, being therefore extraarticular.

Deep infections develop when intraarticular microorganisms are found.

Acute infection is defined as that diagnosed within 4 weeks following KJA while chronic infection is defined as that diagnosed beyond 4 weeks following KJA.

Treatment:

Therapeutic options are shown in Table 4.

Prosthesis Maintenance: two therapy options are available when the prosthesis is to be maintained:

Specific suppression antibiotic therapy, defined according to results of culture and antibiotic sensitivity testing of synovial fluid specimens obtained by aspiration, with low rates of success⁽⁴⁾.

Surgical debridement with polyethylene replacement of the tibial component of the prosthesis is indicated by the authors for selected cases. It is indicated in acute infections of less than 2 weeks' duration, always associated with specific antibiotic therapy for six to eight weeks⁽¹⁶⁾.

Prosthesis Replacement

Immediate replacement: in this case, the patient is submitted to meticulous and extensive surgical debridement with extended synovectomy. All necrotic tissue that is not apparently viable is removed. All prosthesis components are then replaced and orthopedic cement impregnated with antibiotic is used between prosthesis interfaces and bones.

During surgery tissue specimens are collected for culture and antibiotic sensitivity testing; results of these tests are important to define targeted and specific antibiotic therapy. This type of protocol has been shown to be effective in the treatment of infections with advantages associated with shorter hospitalization stays and better functional results since patients submitted to this type of treatment can be referred to rehabilitation within a shorter time⁽³⁾.

Two-step replacement: it is considered the treatment of choice by many schools and is preferred by the authors. The patient is submitted to surgical debridement with removal of all prosthesis components. A spacer of orthopedic cement impregnated with a broad-spectrum antibiotic is inserted within the joint. The antibiotic to be added to cement can be selected according to the most prevalent bacteria in this type of infection, taking into account their pharmacokinetic profile.

The role of the spacer with cement impregnated with antibiotic in the fight against infection is associated with local release of antibiotic and occupancy of intraarticular dead space, thus preventing formation of hematomas, a favorable environment for proliferation and perpetuation of infection.

The use of this spacer aims to prevent retraction of soft tissue. Therefore, placement of the definitive prosthesis is made easier. In authors' protocol, it is modeled with the femoral and tibial components. Flexoextension of the knee joint is then possible, which contributes to a better final functional result. It is kept within the joint for 6 to 8 weeks, in association with systemic antibiotic therapy, defined according to culture testing.

After the first phase of treatment is completed and if there is no clinical or laboratory evidence of infection, the patient is submitted to joint aspiration and arthroscopic biopsy for collection of specimens for culture and antibiotic sensitivity testing. When test results are negative, one may consider the placement of the definitive orthesis. Antibiotic therapy must be maintained for six months in cases of chronic infection⁽⁵⁾.

In case joint aspiration or arthroscopic biopsy is positive, surgical debridement must be repeated and the spacer with cement impregnated with antibiotic must be replaced. Systemic antibiotic therapy must be maintained. Six weeks following debridement, joint aspiration and arthroscopic biopsy are repeated to reevaluate infection control.

Salvage Procedures

Treatment for infection following KJA is not successful in all cases. In immunocompromised patients or in those who develop an extensive involvement of soft tissues or bones due to delay in initiating treatment for infection, the prosthesis must not be maintained or replaced. In these cases, salvage procedures are indicated and aim to partially preserve the function of the leg.

Arthrodesis: it is the most widely used procedure of salvage and consists of the bony union of femur and tibia; plates and screws can be used, as well as intramedullary rods or external fixators, as the authors prefer to do.

Resection arthroplasty: no stabilization method is used. Local fibrosis is expected to produce some joint stability. The use of a leg orthosis is needed.

Amputation: used only in dramatic cases where infections threatens patient's life. Surgery is followed by rehabilitation with the use of an orthosis.

CONCLUSION

Constant efforts have been made in an attempt to reduce infection rates and resulted in the development of treatments offering a painless and stable joint with an acceptable movement range.

The review of worldwide literature shows that the diagnosis and treatment protocol recommended by the authors is associated with the better rate of success since therapy duration is shorter and a lower reinfection rate has been seen, in association with better functional preservation of the joint.

The present study aims to standardize the treatment for infections following total knee joint arthroplasty and is underway. Preliminary results corroborate the results reported in literature.

REFERÊNCIAS BIBLIOGRÁFICAS

Trabalho recebido em 01/12/2003.

Aprovado em 12/08/2004

Work performed at the Orthopedics and Traumatology Department of the University of Sao Paulo School of Medicine.

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Publication Dates

• Publication in this collection
  01 Mar 2005
• Date of issue
  Dec 2004

History

• Received
  01 Dec 2003
• Accepted
  12 Aug 2004