Khalil Allah. Nazem Feb 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.

 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

 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.)

 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 culture II. Histologic III. 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

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

 Variables that must consider before treatment include: I. Deep or superficial II. Duration from T.K.A III. Host factors IV. Soft tissues (extensor mechanism) V. Implant is loose or fixed VI. Pathogens responsible VII. Ability of surgeon VIII. Patient's expectations

 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

I. 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 feasible II. Microorganism has low virulence and susceptible to an oral antibiotic III. The antibiotic can be tolerated without serious toxicity IV. The prosthesis is not loose V. 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

II. Debridement with prosthesis retention This 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 symptoms II. Susceptible gram-positive organism III. Absence of prolonged postoperative drainage or sinus tract IV. 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 2weeks II. Existence of sinus tract III. Hinged prosthesis IV. Immune compromised hosts  Arthroscopy is not suitable surgical method for debridement and retentions

 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

 Advantages: excellent potential for resolving infections alleviating pain, providing stable knee  Disadvantage: elimination of knee motion  Indications: I. high functional demands II. Single joint disease III. Young patients IV. Extensor mechanism disruption V. Poor soft tissue VI. Systemic immunocompromise VII. Bad micro organism Arthrodesis:  Relative contraindication: I. Bilateral knee disease II. Ipsilateral hip or ankle disease III. Over segmental bone loss IV. Contralateral limb amputation

I. IM nailing II. External fixation III. 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

 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

 Is currently the primary accepted method of treatment for infected T.K.A  contraindications: I. persisted or recalcitrant infection II. medical conditions III. extensor mechanism disruptions IV. Poor soft tissue envelope  Reimplantation can be performed as a direct exchange technique or two stages

I. Infection by gram positive II. Absence of sinus formation III. Use of antibiotic cemented IV. 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

 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

 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.

I. Simple tibiofemoral block II. Molded arthrodesis block III. Articulating mobile spacers IV. Medullary dowels

 Usually 4-6 weeks  One of the most important issues is the determination of when it is safe and appropriate to proceed with reimplantation.

 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.