Infected Total Hip Arthroplasty

Husam DarwishSeyon Sathiaseelan

Dr. P. KimDecember 13th 2006

History

• The modern era of arthroplasty is about 30 years old

• Initial series showed infection rates around 9%

• Improvements in air quality in the OR, prophylactic antibiotics, and patient selection have greatly decreased those rates

Economics

• US figures indicate that average cost of revision is $50 000 to $60 000

• 3500 – 4000 infected THA per year• Total cost $150 -$200 million per year

Incidence of Infection

• Reports in the literature range from:– 0.3% (British Medical research council trial)– 2.2% (US Medicare data 1986-1989)

• Some evidence that dedicated institutions with large numbers of THA yearly have lower infection rates ~ 1%

Incidence

• Mayo Clinic data – 1969-1996

THA % Infection rates

Primary 1.3

Revision 3.2

Overall 1.7

Incidence

• Patient factors• OR environment• Surgical factors and technique• Perioperative care

Patient Factors

• Rheumatoid arthritis• Diabetes • Sickle cell anemia – increase rate by 23%• Psoriasis – superficial infection 9.1% deep

infection 5.5%• Renal or liver transplantation – 19%• ESRD on dialysis – 13%• Poor nutrition has been implicated in delayed

wound healing but has not been correlated with deep infection

Surgical Factors

• Increased incidence after revision surgery – 3.2% vs 1.3% in Mayo clinic study for THA

• Any previous surgery– 2.3% vs 0.9% for THA

• Revision for aseptic loosening – 2.5%• Revision with previous infection – 4%• Revision with structural femoral allograft – 5%• Conversion of arthrodesis to THA – 10-13%

Surgical Factors

• Operative time• Avoid dead space and hematoma formation• Minimize tissue trauma

– exposes collagen and basement membrane proteins to the bloodstream which enhances bacterial binding to fibronectin (esp S. aureus)

Peri-operative Care

• Systemic antibiotics• Hill et al – double blind RCT on 2137 THA showed

reduction in infection from 3.3% (placebo) vs 0.9% (5 days cefazolin)

• Nelson et al – demonstrated equal efficacy for 1 day vs 7 days of antibiotics in a randomized trial of 358 patients– Many other similar studies but power is an issue

• Classen et al – large prospective trial showed lowest rate of wound infections with antibiotics given 2 hrs before incision vs just after incision or more than 2 hrs before incision

Recommendations

– ancef 1 g iv 15-30 minutes preop followed by 2-3 postoperative doses

– Further doses intraoperatively if blood loss >2L or >4hrs operative time

– Vancomycin 1g iv for anaphylactic penicillin allergy only followed by one postoperative dose

To drain or not to drain?

• Drains– Willett et al – prospective study of 120 THA

• Drain removed at 24, 48 or 72 hours• 90.9% of total blood loss in first 24 hours• Seven positive deep wound cultures all in

pts with drain removed at 48 or 72 hrs• All deep cultures had growth of identical

organisms on pts skin

– Beer et al – prospective study of bilateral THA (24) and TKA (76)• No difference in swelling or persistent

wound drainage– Kim et al – prospective study of 96 bilateral

THA • Significant increase in wound drainage

and erythema in the undrained hips• No difference in infection rates or

functional outcomes at 1 year

Recommendations

If using a drain, remove at 24 hrs in most situations

Perioperative Care

• Persistant wound drainage– No evidence to support use of prolonged

antibiotics with persistant serous drainage– Permits overgrowth of antibiotic resistant

organisms• Recommendations

– Avoid prolonged postoperative Abx– Compressive bandages and minimize activity to

allow wound to seal– If drainage persists >5-7 days wound debridement

and tissue samples for culture allow for possible prosthesis retention if due to infection

Perioperative Care• Urinary Retention

– Wroblewski et al reported 6.2% deep infection rate in 195 men with postoperative urinary retention vs overall rate of 0.5%

– 59% of those who required catheterization received antibiotic coverage

• Foley removed 24-48 hrs post op has been shown to decrease urinary retention while not increasing UTI

• Recommendations– Pts with urologic symptoms should have them treated

prior to THA– Antibiotic prophylaxis should be given for urinary tract

manipulation in the postoperative period

Routes of Infection

• Direct contamination during OR• Direct or contiguous spread• Hematogenous spread• Reactivation of previous infection

Routes of Infection

• Operating Room Environment– Horizontal laminar air flow – 93% reduction in

airborne bacteria• Clinically decreased infection rates in one

series from 1.4% to 0.9% in THA but increased infection rates from 1.4% to 3.9% in TKA.

– Body exhaust suits – no difference in bacterial counts when used with laminar air flow but 80% reduction vs regular scrubs

Routes of Infection

• Operating Room Environment– Face masks – wearing a surgical face mask in the

sterile core and/or the OR had no effect on the bacterial counts in either the core or the OR

– Head cover – no statistically significant difference between no head cover, caps or hoods

– Contaminated gloves (29%), suction tips (33%), skin blades(9%), needles(10%), surgical gowns(17%), light handles(14%)

– UV light – infection rate of 0.5% for 2389 hips but all OR personnel must be protected from burns

Routes of Infection

• Direct Spread– Organisms migrate to the hip joint from a more

superficial infection • Schmalzried et al – series of 3051 hips with 47

deep infections – 2/47 by direct spread from superficial infection

• Surin et al – series of 803 hips with 34 deep infections – increased risk (3.2X) if there was increased postoperative wound drainage

• Gaine et al – series of 301 hips had no deep infections despite 56 superficial infections

Routes of Infection

• Hematogenous spread– Skin infections – remote from incision– Dental infections– Dental manipulation– Urinary tract infections

• Reactivation– Reactivation of infection in a previously

infected hip or knee

Antibiotic Prophylaxis• Case reports of hematogenous seeding of THA

following dental procedures• Current recommendations of the AAOS

– Prophylactic Abx recommended 1 hour prior to dental procedures during the first two years after surgery

– Immunocompromised pts, RA, SLE, diabetes, hx of infected THA, malnourishment, hemophilia are candidates for lifelong prophylaxis

– Amoxicillin 2 g po or ancef 1 g iv (or clindamycin 600mg po/iv if penicillin allergic) 1 hour prior to dental procedure

Classification of Periprosthetic Hip Infections

• Fitzgerald et al

1. Stage I – acute fulminant infection

2. Stage II – delayed sepsis

3. Stage III – late hematogenous

– Stage I – acute fulminant infection• Within 3 months of surgery• Present with systemic symptoms –

fever, chills, sepsis and unremitting pain even at rest

• Wound drainage, erythema, swelling or abscess

– Stage II – delayed sepsis• Indolent infection within 2 years of

surgery• May originate at time of OR but

presentation delayed due to small inoculum or low virulence of infecting organism

• Most common and most difficult to treat

– Stage III – late hematogenous• Metastatic infections caused by

hematogenous spread• Symptoms of acute infection similar to

stage I in a previously asymptomatic THA

• Seeding can occur regardless of status of fixation of the components

Bacteria

• Infecting organisms can be divided into – Planktonic – individual free floating cells

• Usually early after inoculation • Easier to eradicate

– Sessile – biofilm of glycocalyx • Can adhere to and survive on synthetic surfaces and are

protected from antibiotics, complement activation and ingestion by neutrophils

• Most bacteria in the correct environment can form a biofilm

• Requires time to form after inoculation• Stable prostheses covered with living tissue are less

vulnerable to adherence and biofilm formation

Bacteria

• Biofilm producers– S. aureus– S. epidermidis– pseudomonas

• Poor Biofilm producers– Gram negatives (except pseudomonas)

Bacteria

• S. aureus (27%) and S. epi (28%) are the most common infecting organisms

• Wide range of gm +ve and –ve organisms have been identified including anaerobes and fungus

• S. aureus predominant in early infections• Skin flora bacteria (s. epi, propionobacterium,

peptostreptococci) more common in delayed infections

Virulence and Resistance

• Gram negative bacilli and Group D strep (enterococci) are considered more virulent organisms

• S. epi is generally considered low virulence but may be difficult to eradicate due to glycocalyx - also this species is demonstrating increased antibiotic resistance

• MRSA , VRE, methicillin resistant S. epi infections are becoming increasingly common

Susceptibility to Infection

• Foreign bodies produce an inflammatory and necrotic tissue response

• Response is greater with articulated implants and increases with high levels of wear debris

• Polymethylmethacrylate has been shown to reduce chemotaxis, phagocytosis and killing ability of PMNs

Diagnosis of Infection

• History– Risk factors– Persistent drainage or delayed wound

healing– Constant pain

• Physical– Inflammation, swelling, warmth, erythema,

tenderness– Drainage or persistent sinuses

Laboratory Investigations

• ESR– Measurement of red blood cells that have been caused

to agglutinate by acute phase proteins– ESR>30mm/h - sensitivity 82%, specificity 85% (PPV –

58%, NPV 95%) for the diagnosis of infection– Elevated by other factors including concomitant

infection, inflammatory arthritis, collagen vascular disease, recent surgical intervention (up to 12 months), malignancy

– ESR>30mm/hr 6 months after a two stage revision has a 62% chance of indicating persistent infection

– May be useful as a monitoring tool

Laboratory Investigations

• CRP– Acute phase protein which contributes to

an elevated ESR– Returns to normal within 3 weeks of

surgery with peak levels 2-3 days post op– CRP>10mg/L sensitivity 96% specificity

92% (PPV – 74% and NPV – 99%)• Normal ESR and CRP can reliably rule out

infection • Abnormal ESR and CRP indicate 83%

probability of infection

Laboratory Investigations

• WBC– Rarely elevated in chronic infection– WBC > 11

• Sensitivity 20%• Specificity 96%• PPV 50%• NPV 85%

Radiographic Investigations

• Plain xrays– Often normal in the early stages of infection– Subtle findings may be present

• Periostitis• Localized osteopenia• Endosteal scalloping• Ring osteolysis around wires and cables• Loosening may or may not be associated

with infection

• Periosteal new bone formation

• Focal osteolysis at tip• Faint periosteal

elevation

Radiographic Investigations

• MRI– Presence of signal loss adjacent to the metal

components– Titanium less ferromagnetic than Co-Chromium– Can show periprosthetic abscesses or intrapelvic

extension• US

– Can also be used to detect abscesses and for US guided aspiration of hip/abscess for diagnosis

– Thickened capsule may indicate infection

Radiographic Investigations

• Radionuclide Scans– Tc 99m bone scan is sensitive but not specific– Normal scan should rule out infection or loosening– Abnormal in both infection, loosening, for up to 1

year post operatively, heterotopic ossification, inflammatory conditions, fractures and tumours

– In labelled WBC scans are sensitive at diagnosing conditions with increased vascularity and WBC uptake but can be negative in chronic infection due to poor uptake

• PPV – 54-63%, NPV – 95%

Invasive Diagnostic Tests

• Aspiration– Can confirm the presence of infection and identify

the organism(s) involved and antibiotic sensitivities– Should be done prior to administration of

antibiotics or two weeks since last dose– Sensitivity 92%, specificity 97%, accuracy 96%– Gram stain, cell count, glucose, protein, lactic

acid?– If cell count >25 000 leukocytes/ml and >25 %

PMNS infection suspected– Allows arthrogram at the same time

Hip Arthrogram

• Deep delayed infection in 84 yo man

• Acetabular migration• Long sinus tract extending

posterior to femoral shaft

Emerging Molecular Biological Techniques

• Interleukin-2 and gamma interferon• PCR of aspirate to detect remnants of

bacterial DNA or RNA– Difficult to determine whether bacteria are

live or dead• Serologic markers for specific infections

Intraoperative Tests• Grossly abnormal tissues at time of revision surgery

despite a negative workup - sensitivity 70% and specificity 87%

• Send immediate gram stain – Sensitivity 19%, specificity 98%, PPV 63%, NPV 89%

• Culture of synovial fluid• Frozen section of inflamed tissue >5 PMNs per hpf

– Sensitivity 80-100% specificity 94-96%• Intraoperative Cultures

– Gold standard - sensitivity 94%, specificity 97%, PPV 77%, NPV 99%

– At least 3 tissue samples – Swab cultures from the removed inplant are less

sensitive

Algorithm for Infection• High index of suspicion• History and physical and xrays• ESR and CRP

– If normal – no further tests– If abnormal – hip aspiration under flouroscopy

• Aspirate – If normal but high index of suspicion

• Repeat aspirate with arthrogram or US or biopsy• If all tests normal but high index

– May resort to intraoperative methods– If frozen section negative – may proceed with revision

Treatment

• Consists of one or more of the following

– Incision and drainage– Antibiotic therapy– Excision arthroplasty– One or two stage revision

Treatment

• Incision and drainage– Often used as initial treatment in acute early or late acute

hematogenous infections• Retention rates in early acute infection – 26-71%• Retention rates in late acute hematogenous infection –

26-50%• Duration of symptoms correlates with success rates

– Brandt et al – 56% retention if treated within 2 days – 13% retention if treated after 2 days of symptoms

• All components must be well fixed, any loose components must be removed

• Poly exchange– In chronic periprosthetic infection failure rate is 95-100%

Treatment

• Antibiotic suppression– Small series involving patients who were deemed

to be unsuitable for reconstruction or who had refused reconstruction – 37% revision rate

– May be an option for pts who refuse OR or are medically unsuitable

• Infection should not produce systemic symptoms, prosthetic components should be well fixed, organism should be sensitive to po Abx

Treatment

• Excision Arthroplasty– Most predictable procedure to eradicate infection– Bourne et al – 1/33 reinfection rate– Functional outcome is very poor including

decreased active range of motion and strength– Oxygen consumption higher than an above knee

amputation for THA– May allow for some ROM at knee but severely

limits walking ability– Salvage procedure to provide some pain relief in

patients not suitable for reconstruction

Reimplantation

• Two Stage Exchange Arthroplasty– Provides a better environment for

eradication of infection– Organisms may be cultured from tissue

samples which allows for further microbiological assessment and adjustment of antibiotics

– Goal is to prevent a complex reconstruction in the presence of unresolved sepsis

Two Stage Revision• First stage is essentially an excision arthroplasty

– May use antibiotic loaded cement as a temporary spacer• Allows some function and reduces soft tissue

contracture• Minimum 6 weeks of antibiotics

– Response to treatment is assessed by ESR, CRP• Mont et al proposed use of aspiration biopsy to confirm

eradication– May rarely require second debridement

• Second procedure is the reimplantation– Again send tissue for C&S and frozen section (specificity

– 98% sensitivity – 25%)

Revision

• Use same operative approach • Dislocate hip joint to facilitate removal of all

infected and necrotic tissue• Components examined for loosening• Components and all cement are removed • Check cement mantle carefully for any

retained cement• May require intra-pelvic approach if cup and

cement mantle have protruded into pelvis

Prostalac

• Prosthesis of antibiotic loaded acrylic cement• Most recent version consists of a constrained

cemented acetabular component and a modular femoral component that are covered intraoperatively with antibiotic loaded cement using a series of molds

• Acetabular component is loosely cemented and femoral component is press fit for ease of removal

Antibiotic Impregnated Bone Cement

• To preserve the biomechanical properties of bone cement the antibiotics are added in powder form

• Up to 2 g of oxacillin, cefazolin, or gentamicin in a single batch of cement does not significantly alter the compressive or tensile strength of the cement

• Aqueous gentamicin interferes with the early prepolymerizing process during mixing and significantly reduces the strength

• Doses > 4.5 g of gentamicin powder per cement batch decreased the compressive strength below 70 MPa

• Recommendations

– not currently recommended for prophylaxis in primary THA

– benefit in revision surgery

Antibiotic Impregnated Cement

• Choice of Antibiotic– Tobramycin

• Predictable elution from cement at bactericidal levels

– Vancomycin• Erratic elution from cement• May be combined with tobramycin

– Gentamicin• Predictable elution from cement

– A combination of two antibiotics may improve the elution of both agents

Antibiotic Beads

• Cement beads may be used between stages of 2 stage revision

• 8-9 g of antibiotic powder per cement package may be used

• May be extremely difficult to remove

Antibiotic Impregnated Bone Cement

• Josefsson et al – prospective study comparing systemic antibiotics vs gentamicin impregnated cement– At 10 yrs – 1.6% vs 1.1%

• Scandinavian Hip Registry – gentamicin cement had lowest risk ratio for revision

• Norwegian hip review – 10 611 THA for OA – failure rate ratio for infection – Systemic Abx + Abx bone cement – 1.0– Systemic Abx alone – 4.3– Abx bone cement alone – 6.3– No prophylaxis – 11.5

• Lynch et al – retrospective review of 1542 THAs showed 4% infection rate for revision arthroplasty with plain cement vs 1.8% with antibiotic cement

Two Stage Revision

Results of Two Stage Revision

• Timing of second stage is controversial– Must be no further evidence of infection

• Some evidence to suggest that earlier reimplantation may have better results– Coyler – 22%(2 of 9) reinfection with

reimplantation at 22 weeks vs 14%(4 of 28) within 6 weeks

• 82% success without antibiotic cement vs 90% with (Hanssen and Rand)

Two Stage Revision of an Uncemented Prosthesis

• uncemented fixation avoids the challenging reoperation of the long stem cemented prosthesis

• Results are generally inferior to cemented • Average infection rates 12-18% • Forfeit the benefit of antibiotic impregnated

cement

Two Stage Revision of Uncemented Prosthesis

Reimplantation

• Single Stage Exchange Arthroplasty– Indications based on a series by Salvati et al

• Subacute sepsis caused by a sensitive bacteria in an immunocompetent patient who has good soft tissue and bone stock to assure a successful biomechanical reconstruction

• 5-10% recurrence rate• Meticulous debridement is critical • Antibiotic loaded cement (success rate of 83%

with and 60% without)• iv antibiotics for a minimum of 6 weeks

– May also be indicated for elderly pts who could not tolerate a two stage procedure

One vs Two Stage

• Advantages– Less morbidity– Reduction in cost– Technically easier– Quicker rehabilitation

• Disadvantages– Unable to direct antibiotic in

cement to specific organism– Unable to observe pts

response to therapy– Higher reinfection rate– Only one debridement– Able to eradicate distant sites

of infection– Informed decision whether

disability from resection justifies risks of revision

Bone Allograft

• Chronic infection may produce significant femoral and or acetabular bone loss

• Bone graft could act as a sequestrum • Increased infection rates in primary THA with bone

grafting – Could be related to confounding factors such as

complexity of OR, increased OR time, disease transmission by the graft

• Reported reinfection rates range from 7.5-11%• May be able to use morcellized bone graft as a carrier

of antibiotics

Treatment

• Positive intraoperative cultures at the time of revision without any preceding evidence of infection– Tsukuyama et al reported on 31 pts treated with 6

weeks of iv antibiotics• 5/31 (16%) had recurrence of infection at 2

years– Dupont 6/15 (40%) recurrence without additional

antibiotics

Treatment of Reinfection after Reimplantation

• Very poor prognosis– Series by Pagnano et al – 38% reinfection rate for further

reconstruction– Pts who underwent reconstruction and had

reinfection had the worst functional outcomes

• Excision arthroplasty is the preferred treatment

Prevention of Infection

• Principles– Augment the host response– Optimize the wound environment– Decrease the bacterial load introduced into

the surgical wound

Thank you