The infected T.K.R

Khalil Allah. NazemFeb 2013

In the face of an increasing prevalence of TKA, intensified efforts at infection prevention seem logical to reduce the overall burden of PJI.

As an over view, prevention of PJI relies upon Augmentation of the host response Optimization of the wound

environment Reduction of bacterial contamination

in the pre-intra and post operation times

In addition to prevention, a thorough understanding of the principle of diagnosis and treatment is essential

Although the incidence rates of infection following TKR appear to have fallen over the past several decades, the reported incidence varies in many studies

Many inherent patient risk factors are known to predispose toward post operative deep infection. Host factors include a diagnosis of RA, skin ulcers, D.M ,history of malignancy, obesity, smoking, renal or liver transplantation, HIV positive, prior open knee surgery or periarticular Fx, prior septic arthritis or osteomyelitis.

Risk factors related to surgeon: Increased INR after operation

hematoma require reoperation early wound healing complications

Recent intra articular injection of corticosteroide .

Prolonged operative time

Proper use of AnB prophylaxis represents the single most effective method of reducing infection in TKR.

Optimization of surgical environment. Use low dose ABLC in high risk patients

and revision surgery. Frequent irrigation. Carful surgical technique. Excellent wound closure is important

variables under the surgeon control

Risk factors related to surgeon:

Hematogenous infection of TKR in early postoperative period or many years after operation is often influenced by the surgeon through education efforts made with arthroplasty patients. (Oral- genitourinary- gastrointestinal)

In general invasive procedures that potentially cause bacteremia should simply avoided in the first 3-6 months.(Dental procedures greater than 75 minute in DM and RA are at higher risk). AAOS no longer has published guidelines for the use of prophylactic AnB for high risk patients (Antibiotic prophylaxis for bacteremia in patients with joint replacement.)

Diagnosis

No criteria for the definitive diagnosis of PJI have attained universal agreement

It is well recognized that some true PJI have negative culture (up to 19%)

Current definition of PJI includes a combination of clinical sign and symptom, histologic analysis of tissue and results of cultures

The diagnosis of definitive PJI is made if evaluation established at least one of the following criterion

I. Two or more positive cultureII. HistologicIII. Gross purulent is observed IV. Actively discharge sinus tract

It seems reasonable to identify offending organism and enacting directed treatment strategies

In most series gram positive , may polymicrobial (9%), in current era many resistant organism

MRSA and MRSE have emerged as common nosocomial pathogens often requiring complex AnBs and potentially inferior treatment outcome

Resistant Infections definitely need two staged operations

Fungal PJI are rare and needs two staged treatment

Identification and diagnosis of biofilm organisms is difficult

I. Culture independent molecular method (detection of 16s ribosomal deoxy ribonucleic acid)

II. Culture samples obtain by sonication of prosthesis

Timing of the clinical presentation is a critical factor in diagnosis

These various clinical presentation is critical factor and classified as a useful guide to selecting the most appropriate treatment option

Classification System of Prosthetic Joint Infection: Time to Onset of Infection Dictates Treatment

Classification System of Prosthetic Joint Infection: Time to Onset of Infection Dictates Treatment

Treatment

Variables that must consider before treatment include:

I. Deep or superficialII. Duration from T.K.AIII. Host factorsIV. Soft tissues (extensor mechanism)V. Implant is loose or fixedVI. Pathogens responsibleVII. Ability of surgeonVIII.Patient's expectations

Treatment goals

Eradication of infection, alleviation of pain, maintenance of function

When confronted with an infected T.K.A, the treating physician should start by considering the question prosthesis retain or removal

Treatment methods where the prosthesis is retainedI. Antibiotic suppression:This method alone will not

eliminate deep infection but can be used as suppression treatment when the following criteria are met

I. Prosthesis removal is not feasibleII. Microorganism has low virulence and susceptible to an

oral antibioticIII. The antibiotic can be tolerated without serious toxicityIV. The prosthesis is not looseV. Other prosthesis or cardiac valvular prosthesis are not

present Success rates are 16-24% Rifampin with a quinolone has been reported to be more

successful

Treatment methods where the prosthesis is retainedII. Debridement with prosthesis retentionThis method indicated only in infections in early post operative

period or acute hematogenous with fixed and functional prosthesis and patient has this criterion

I. Short duration of symptomsII. Susceptible gram-positive organism III. Absence of prolonged postoperative drainage or sinus tractIV. No prosthesis loosing V. No other arthroplasty or cardio vascular prosthesis

Success rates are 19-32% Factors that worsen the results are

I. Post operative drainage longer then 2weeksII. Existence of sinus tractIII. Hinged prosthesisIV. Immune compromised hosts

Arthroscopy is not suitable surgical method for debridement and retentions

Treatment methods where by the prosthesis is removed Resection arthroplasty:

The ideal candidate is a patient with polyarticular RA with limited ambulatory demands, which allow the patient to sit more readily than is feasible with a knee arthrodesis. The primary disadvantage is mobility and pain during transfer or ambulation

Treatment methods where by the prosthesis is removed

Advantages: excellent potential for resolving infections alleviating pain, providing stable knee

Disadvantage: elimination of knee motion Indications:

I. high functional demandsII. Single joint diseaseIII. Young patientsIV. Extensor mechanism disruption V. Poor soft tissueVI. Systemic immunocompromiseVII. Bad micro organism

Arthrodesis:

Relative contraindication:I. Bilateral knee diseaseII. Ipsilateral hip or ankle

diseaseIII. Over segmental bone lossIV. Contralateral limb

amputation

Method of Arthrodesis:

I. IM nailingII. External fixationIII. Dual plate fixation IM nailing appears to show a higher

trend toward success union but has a higher risk of recurrent infection compare to ext fixation

Amputation

Is rarely indicated except in cases if life threatening systemic sepsis or persistent local infection associated with massive bone loss.

Factors must commonly leading to amputation include multiple revisions sever bone loss, intractable pain

Reimplantation

Is currently the primary accepted method of treatment for infected T.K.A

contraindications:I. persisted or recalcitrant infectionII. medical conditionsIII. extensor mechanism disruptionsIV. Poor soft tissue envelope

Reimplantation can be performed as a direct exchange technique or two stages

Factors associated with successful direct exchange:

I. Infection by gram positiveII. Absence of sinus formationIII. Use of antibiotic cementedIV. A prolonged 12week course of AB

therapy This method indicated only in

groups of patients highly selected by arthroplasty surgeons familiar with the treatment of prosthetic infection

Two stage reimplantation

This protocol consist of soft tissue debridement and removal of infected prosthesis and cement, followed by 6weeks IV antibiotics and subsequent reimplantation

The success rate is 85-95% Use of adjunctive antibiotic delivery

provided by the ABLC gradually lead to decrease AB duration and shorter time delays prior to reimplantation

Antibiotic cement spacers Low dose ABLC (<2g per 40g) should be used for

prophylaxis in reimplantation or primary T.K.As in high risk patients or for prosthetic fixation at reimplantation

The higher dose rations should be reserved for treatment of active infection with spacer

AB elution increase by prosity of cement and mixing with another AB 3.6 gr of tobramycin + 1gr vancomycin in 40gr cement are good

The primary function of block spacer include delivery of local AnB and maintenance of collateral ligament length

Potential disadvantages include presence of a foreign body and bone loss incurred.

Different types of block spacers:

I. Simple tibiofemoral blockII. Molded arthrodesis blockIII. Articulating mobile spacersIV. Medullary dowels

Molded arthrodesis block

Time period between resection and reimplantation

Usually 4-6 weeks One of the most important issues is

the determination of when it is safe and appropriate to proceed with reimplantation.

Guidelines:

C.R.P, ESR Open biopsy or aspiration It is preferable to utilize intraoprative

decision making based on the appearance of the knee joint supplemented by analysis of frozen section

If concern arises about the presence of persistent infection, it is prudent to perform other debridement inserted new ABLC spacers, closed the wound, and await the results of culture and sensitivity testing.