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Introduction
  • Epidemiology 
    • incidence   
      • primary joint replacement
        • 1-2% TKA vs. 0.3-1.3% THA
      • revision joint replacement
        • 5-6% TKA vs. 3-4% THA
    • risk factors 
      • pre-operative
        • active infection
          • local cutaneous, subcutaneous, deep-tissue or joint infection 
          • systemic septicemia
        • previous local surgery/prior local infection 
      • postoperative
        • immune suppression
          • immunosuppressant drugs
            • anti-TNF agents (e.g. infliximab, etanercept, adalimumab, certolizumab, golimumab)
            • antimetabolites (e.g leflunomide)
            • corticosteroids
          • immunosuppressive conditions (dysplasia or neoplasia)
            • poorly controlled diabetes mellitus (HBA1c >7)
            • chronic renal disease
            • acute liver failure
            • malnutrition (eg. albumin <3.5; total serum leukocytes <800)
            • HIV (CD4 counts <400)
        • inflammatory arthropathy
          • rheumatoid arthritis
          • psoriasis
          • ankylosis spondylitis
        • lifestyle factors
          • morbid obesity
          • smoking
          • excessvice alcohol consumption
          • intravenous drug use
          • poor oral hygiene 
  • Pathophysiology
    • most common bacterial organism include
      • staphylococcus aureus 
      • staphylococcus epidermidis
      • Coagulase-negative Staphylococcus (chronic infections)
    • most common fungal pathogen 
      • Candida species (e.g. Candida albicans)
  • Prophylaxis
    • screening
      • screen and optimize risk factors
      • nasal mupirocin for decolonization of nasal MSSA/MRSA
      • routine urine cutures NOT warranted pre-operatively, unless history or symptoms of UTI
      • stop DMARDs 4-6 weeks prior to surgery  
      • revision joint replacement 
        • normalized ESR, CRP off antibiotics
    • operatively
      • pre-operative skin cleansing with antiseptic wash
      • systemic antibiotics 
        • administered within 30 minutes to incision, and >10 minutes prior to tourniquet
        • continued for 24 hours after surgery 
      • operative room
        • vertical laminar airflow systems 
        • limit hospital personal OR traffic in-and-out of room
    • post-operatively
      • antibiotics prior to dental work is dependant on host risk factors 
Classification
  • Time of onset
    • Acute infection
      • infection within 3-6 weeks from surgery
        • CDC definition < 90 days from date of joint replacement
      • biology
        • usually confined to joint space
        • no invasion into prosthetic-bone interface
        • no biofilm production
      • S. aureus commonly associated with acute THA PJIs
    • Chronic infection
      • infection more than 3-6 weeks from surgery
        • CDC definition > 90 days from date of joint replacement
      • biology
        • biofilm created by all bacteria forms on implant within four weeks
          • composition
            • 15% cells and 85% polysaccharide layer (glycocalyx) 
            • glycocalyx allows biofilm to adhere to prosthesis and sealoff infection and protect bacteria from host immune system
          • consequence
            • no method exists to safety remove biofilm and eradication is difficult
            • prosthetic explant indicated with infection >4 weeks due to biofilm
          • infection has invaded prosthetic-bone interface
        • S. epidermidis most common organism in chronic THA PJIs
  • Source of infection
    • Direct invasion
      • sinus tract into joint capsule
      • wound dehiscence
    • Hematogenous infection
      • infection in a longstanding infection-free joint secondary to another infection (eg. dental work, infected gallbladder)
Presentation
  • History
    •  may have history of the following
      • recent or active bacteremia
      • multiple local surgeries
      • skin/epithelial tissue penetration (eg. IV drug use, colonoscopy, dental work, ulceration, wound complication)
  • Symptoms
    • persistent pain and stiffness at site of arthroplasty is associated with infection in >90% of patients
    • acute onset with swelling, tenderness, and drainage 
    • chronic infections show pain and more subtle symptoms
      • function deteriorates over time
      • pain worsens over time
  • Physical exam
    • inspection
      • sinus tract to the joint is a definite infection
      • warmth, redness, or swelling  
      • low grade fever
    • motion
      • limited by pain and swelling
Imaging
  • Radiographs
    • findings  
      • periosteal reaction 
      • scattered patches of osteolysis
      • generalized bone resorption without implant wear
      • transcortical sinus tracts
      • implant loosening
  • Bone scan
    • modalitity
      • Tc-99m (technetium) detects inflammation and In-111 (indium) detects leukocytes
      • triple scan can differentiate infection from fracture or bone remodeling
    • indications
      • if infection is suspected, but cannot be confirmed by aspiration or blood work
    • sensitivity and specificity
      • 99% sensitivity and 30% to 40% specificity
  • Positron emission tomography (PET)
    • indication
      • may help to identify areas of high metabolic activity using fluorinated glucose
    • sensitivity and specificity
      • 98% sensitivity and 98% specificity
MSIS Criteria
  • Musculoskeletal Infection Society (MSIS) analyzed the available evidence to propose a new definition for prosthetic joint infections
    • Major criteria (diagnosis can be made when [1] major criteria exist)
      1. sinus tract communicating with prosthesis, or
      2. pathogen isolated by culture from 2 separate tissue/fluid samples from the affected joint
    • Minor criteria (diagnosis can be made when [4/6] of the following minor criteria exist)
      1. elevated ESR (>30mm/h) or CRP (>10mg/L)
      2. elevated synovial WBC (>1,100cells/ul for knees, >3,000cells/ul for hips)
      3. elevated synovial PMN (>64% for knees, >80% for hips)
      4. purulence in affected joint
        • this finding alone is insufficient
          • fluid from metal-metal articulation, gout, etc. can resemble pus
      5. pathogen isolation in 1 culture
      6. >5 PMN per hpf in 5 hpf at x400 magnification (intraoperative frozen section of periprostehtic tissue)
Studies
  • Labs
    • Blood panel
      • WBC
        • not specific or sensitive
    • ESR and CRP  
      • CRP
        • physiology
          • peaks 2-3days after surgery
          • returns to normal at 21 days (3 weeks)
        • normal range
          • acute (< 6 weeks from surgery) = <100 mg/L
          • chronic (> 6 weeks from surgery)= <10 mg/L
      • ESR 
        • physiology
          • peaks 5-7 days after surgery
          • returns to normal 90 days (3 months)
        • normal range
          • acute (< 6 weeks from surgery) = no consences
          • chronic (> 6 weeks from surgery)= <30 mm/hr
    • Serum interleukin-6 (IL-6, normal <10pg/mL)
      • physiology
        • peaks 8-12h after surgery
        • returns to normal 48-72h after surgery (3 days)
        • less commonly followed, but can monitor and follow the progress of infection
      • outcomes
        • has been shown to have the highest correlation with periprosthetic joint infection
        • sensitivity 100%, specificity 95%
        • false positives
          • RA
          • multiple sclerosis
          • AIDS
          • Paget's disease of bone
  • Joint aspiration
    • indications
      • whenever there is a strong suspicion in order to confirm the diagnosis 
    • lab order request
      • cell count and differential
      • crystals
      • gram stain
      • cultures and specificity
    • outcomes
      • cell count and differential
        • lowest serologic values suggestive of infection   
          • synovial WBC >1,100 cells/ul and PMN >64% in knees
            • synovial WBC >27,800 cells/ul in the first 6 weeks after TKA suggestive of infection
          • WBC >3,000 cells/ul and PMN >80% for hips
      • gram stain  
        • stain for bacteria in sample
        • specificity > sensitivity
          • positive test would be indicative of infection, however a negative test does not rule out infection
      • repeat aspiration 
        • indicated in cases of inconclusive aspirate and peripheral lab data  
    • other tests
      • alpha-defensin immunoassay test 
      • leukocyte esterase colorimetric strip test
  • Peri-operative analysis
    • microbiology
      • definitive diagnosis can be made if the same organism is obtained by repeat aspirations or at least 3 of 5 periprosthetic  specimens obtained at surgery
        • complications
          • false-positive rate is 8%
          • tissue sample better than swabs
    • histology
      • Intraoperative frozen section
        • indications
          • equivocal cases with elevated ESR and CRP or suspicion for infection
          • sensitivity 85% and specificity 90% to 95%  
          • >5 PMNs/hpf x 5 hpf is probable for infection
Treatment
  • Nonoperative
    • chronic suppressive antibiotic therapy
      • indications
        • unfit for surgery 
        • refuse surgery
        • systemic spread and maintain joint motion with symptomatic relief
      • outcomes
        • 10% to 25% success rate of eradication
        • 8% to 21% complication rate
  • Operative
    • polyethylene exchange with component retention, IV abx for 4-6 weeks 
      • indications
        • acute infection (<3 weeks after surgery)
        • acute hematogenous infection (weak literature, ideally <48-72hrs from symptom onset)
      • techniques
        • thorough tissue debridement and irrigation with large-volume of irrigant
      • outcomes
        • 50% to 55% success rate
        • implants must be removed if reinfection documented
        • Dependant of bacteria speciation  
    • one-stage replacement arthroplasty
      • indications
        • used more commonly in Europe for infected THA
        • no sinus tract, healthy patient and soft tissue, no prolonged antibiotic use, no bone graft
        • low-virulence organism with good antibiotic sensitivity
      • technique
        • use antibiotic-impregnated cement
      • advantages
        • lower cost and convenience with single procedure
        • earlier mobility
      • disadvantages
        • higher risk of continued infection from residual microorganisms
      • outcomes
        • variable success of 75-100%
    • two-stage replacement arthroplasty 
      • indications 
        • gold standard for an infected joint >4 weeks after arthroplasty
        • must be medically fit for multiple surgeries
        • requires adequate bone stock
        • requires confirmation of microbial eradication
          • benign clinical exam
          • normal labs (WBC, ESR, and CRP)
          • negative aspiration cultures
            • obtain repeat cultures at least two weeks after planned antibiotic course has been completed
      • techniques (see section below)
        • prosthesis removal, antibiotic spacer, IV antibiotics for 4-6 weeks and delayed reconstruction
      • outcomes
        • bilateral TKA resection arthroplasty followed by 6 weeks of antibiotics and bilateral reimplantation has excellent results at 2-year follow-up 
        • early reimplantation within 2 weeks has 35% success rate
        • delayed reimplantation >6 weeks has a 70-90% success rate
        • cementless reimplantation in the hip has better outcomes than cemented
    • resection arthroplasty
      • indications
        • poor bone and soft tissue quality
        • recurrent infections with multi-drug resistant organisms
        • medically unfit for multiple surgeries
        • failure of multiple previous reimplantations
        • elderly nonambulatory patients
      • disadvantages
        • short limb, poor function, and patient dissatisfaction
      • technique
        • remove all infected tissue and components with no subsequent reimplantation
      • outcomes
        • total knee success rate is 50% to 89%
        • total hip success rate is 60% to 100%
    • arthrodesis 
      • indications
        • reimplantation is not feasible due to poor bone stock 
        • recurrent infections with virulent organisms
      • outcomes
        • 71% to 95% success rate with bony fusion and infection eradication
    • amputation 
      • indications
        • total knee infections recalcitrant to other options
        • severe pain, soft tissue compromise, severe bone loss, or vascular damaged
      • technique
        • AKA
Techniques
  • Surgical debridement and polyethylene exchange
    • debridement
      • modular parts should be removed to remove fibrin layer between plastic and metal parts which acts as a nidus of infection
    • polyethylene exchange
      • be sure component available
  • Two-stage replacement arthroplasty
    • prosthetic explant
    • surgical debridement
      • must debride bone implant interface and soft tissues
    • antibiotic spacer and IV antibiotics
      • advantages of spacers
        • reduce joint dead space, provide stabilty, and deliver high dose antibiotics
      • disadvantages of spacers
        • potential local or systemic allergic reactions
        • increased chance of developing antibiotic-resistant organisms
        • only heat-stable antibiotics can be added to cement
      • static or dynamic (articulating) spacers can be used
      • advantages of static spacers
        • allow delivery of higher doses of antibiotics (not premade)
        • better wound healing (no joint motion)
      • advantages of articulating spacers  
        • decreased reimplantation exposure time
        • better maintenance of joint space and motion
        • decreased quad shortening
        • better patient satisfaction
        • both spacer types have equivalent functional outcomes and rate of infection recurrence
      • spacer antibiotics
        • each 40 g bag of cement should have 3 g of vancomycin and 4 g of tobramycin added
          • gentamycin may be substituted for tobramycin
        • elution of antibiotics depends on cement porosity, surface area (beads increase area), and antibiotic concentration 
        • must use heat stable antibiotics (vancomycin, tobramycin, gentamicin)
      • IV antibiotics
        • wait to administer intraoperatively until aspiration  and cultures taken
        • must be administered for 4 to 6 weeks after explant
        • initial empiric regimen
          • first-generation cephalosporin
          • vancomycin (if any of the following are true)
            • true allergic sensitivity to penicillin
            • prior history of or documented exposure to MRSA
            • unidentified organism
        • tailor the regimen based on microorganism and susceptibility testing
    • reimplantation
      • send tissue specimens for culture and frozen section pathology
      • implant only if all preoperative and intraoperative measures are acceptable
      • if intraoperative frozen section demonstrate acute inflammation, debride the wound, reapply cement spacer, and return later
      • when using cement, use antibiotic-impregnated cement
Local Antibiotics 
  • Properties
    • active against the organism
    • can be incorporated into delivery vehicle (PMMA)
    • thermo stable (will not denature during exothermic polymerisation reaction)
  • Choices
    • aminoglycosides (gentimicin, tobramycin)
      • effective against gram-negative bacilli
      • synergistic against gram-positive cocci (Staphylococcus, Enterococcus)
      • low risk of systemic toxicity
    • Vancomycin
      • effective against gram-positive cocci
      • excellent elution properties
  • Doses
    • low dose = 2g antibiotics:40g of cement
      • commercial antibiotic cement is low dose
        • Cobalt G-HV (Biomet)
        • Palacos R+G (Zimmer)
        • Simplex P (Stryker)
        • Cemex Genta (Exactech)
        • SmartSet GMV (Depuy)
        • VersaBone AB (Smith & Nephew)
    • high dose ≥ 3.6g antibiotics:40g of cement
      • highest doses without systemic toxicity
        • 12.5g tobramycin:40g cement
        • 10.5 vancomycin:40g cement
    • practical dose
      • vancomycin is 1g per vial, tobramycin is 1.2g per vial
      • use 3g vanco and/or 3.6g tobramycin in 40g cement
        • use extra liquid monomer (1.5-2 ampoules monomer : 1 bag cement)
  • Elution properties
    • rapid release in initial 24h
    • followed by rapidly decline in release rate
      • combination dosing (both tobramycin+vancomycin) increases release rate of antibiotics (more than if each were used alone)
    • low levels at 5 weeks
    • experimental models do NOT show difference in elution/concentrations in conventional wound closure vs negative-pressure wound therapy (NPWT)
  • Mixing
    • vacuum mixing 
      • removes air bubbles
      • enhances mechanical properties
      • may increase/decrease antibiotic elution rates
    • hand mixing
      • may lead to uneven distribution of antibiotics within cement and inconsistent release
    • sequence of ingredients
      • adding vancomycin powder after cement powder + liquid monomer mixed for 30s results in greater elution
  • Newer techniques
    • vancomycin powder directly into wounds (mostly in spine literature)
    • antibiotic cement coated IM nails
    • local antibiotics bonded to implant surface
Complications
  • Failure to eradicate infection
 

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Questions (54)
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(OBQ09.45) A 65-year-old male presents with a painful right total knee arthroplasty, which was performed ten years ago. CRP is 15 mg/L. Knee aspiration reveals a purulent fluid with 3,100 WBC's with 83% PMN's. Culture results are pending. Which of the following is the best management option? Review Topic

QID: 2858
1

Physical therapy, ice, and follow-up evaluation in 2 weeks

5%

(114/2418)

2

Repeat aspiration if cultures are positive

11%

(266/2418)

3

Oral antibiotics

0%

(6/2418)

4

Intravenous antibiotics

3%

(65/2418)

5

Surgical explant of components

81%

(1959/2418)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5
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(OBQ06.184) Which of the following total hip arthroplasty patients appropriately meets the criteria for a surgical debridement with isolated femoral head and polyethylene liner exchange? Review Topic

QID: 370
1

Prosthesis infection of 4 months duration

0%

(10/2438)

2

Prosthesis infection 8 weeks following implantation

10%

(237/2438)

3

Prosthesis infection 3 days following a systemic infection

87%

(2121/2438)

4

Acetabular component loosening due to osteolysis

2%

(40/2438)

5

Vancouver Type A periprosthetic fracture.

1%

(21/2438)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3
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(OBQ11.46) A 68-year-old woman underwent a right total knee arthroplasty 5 years ago and has increasing right knee pain over the past 2 months. Radiographs are seen in Figures A and B, respectively. Laboratory studies demonstrate a C-reactive protein of 10 mg/dL (normal < 2.0 mg/dL) and an erythrocyte sedimentation rate of 50 mm/h (normal < 20 mm/h). Knee aspiration shows white blood cell count of 3,400/mm3 with 90% polynuclear cells. The patient's gram stain and cultures are negative. What is the most appropriate next step in management? Review Topic

QID: 3469
FIGURES:
1

Irrigation and debridement with polyethylene spacer exchange

4%

(123/2897)

2

One-stage revision

1%

(42/2897)

3

Two-stage revision

91%

(2650/2897)

4

One-stage revision with antibiotic impregnated cement

2%

(59/2897)

5

One-stage revision with direct antibiotic infusion into knee joint via hickman catheter

0%

(11/2897)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(OBQ04.121) A 58-year-old man has significant pain and stiffness after undergoing right total knee arthoplasty 6 months ago. A current radiograph and bone scan are shown in Figures A and B. Labs show an ESR of 45mm/hr (normal 0-20) and a CRP of 13.5 mg/l(normal <10). Knee aspiration reveals a WBC count of 850 cells/mm(3) with 70% polymorphonuclear cells and no growth on culture. What is the next most appropriate step in management? Review Topic

QID: 1226
FIGURES:
1

Two-stage component removal, antibiotic spacer placement and subsequent revision

17%

(324/1856)

2

Observation with repeat ESR and CRP in one week

17%

(309/1856)

3

Surgical debridement and polyethylene exchange only

4%

(75/1856)

4

Repeat aspiration and culture

59%

(1088/1856)

5

One-stage irrigation and debridement with exchange of all components

3%

(51/1856)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(OBQ10.54) A 64-year-old female underwent a total knee arthroplasty 4 years ago and has increasing pain for the past 6 months. Knee aspiration reveals 4,000 leukocytes with 80% polymorphonucleocytes and a 2-stage revision arthroplasty is planned. When comparing articulating cement spacers to static spacers following resection, all of the following are potential advantages of articulating spacers EXCEPT Review Topic

QID: 3142
1

Decreased quadriceps shortening

1%

(20/2227)

2

Decreased rate of infection recurrence

87%

(1933/2227)

3

Increased knee range of motion for duration of cement spacer implantation

4%

(91/2227)

4

Better maintenance of joint space

2%

(43/2227)

5

Decreased exposure time during reimplantation

6%

(136/2227)

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PREFERRED RESPONSE 2
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(OBQ05.165) A 64-year-old woman with osteoarthritis underwent bilateral total knee replacement 3 years ago. Current radiographs are shown in Figure A. She reports a 3-month history of bilateral knee pain while at rest and increasing swelling in the knees. Her ESR and CRP are elevated and bilateral knee aspiration cultures reveal Staphylococcus aureus. What is the most likely outcome if the patient undergoes simultaneous, bilateral knee resection arthroplasty with cement spacer and a course of intravenous antibiotics? Review Topic

QID: 1051
FIGURES:
1

Prosthesis reimplantation with need for multiple surgical debridements at 2-year follow-up

5%

(45/877)

2

20% risk of above knee amputation

5%

(41/877)

3

Retention of antibiotic cement spacer and low chance of successful prosthesis reimplantation at 2-year follow-up

9%

(76/877)

4

50% rate of conversion to knee fusion following resection arthroplasty

5%

(44/877)

5

Successful prosthesis reimplantation at 2-year follow-up with less than 20% revision rate

76%

(668/877)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

(OBQ12.263) Increasing the porosity of a cement spacer for an infected total knee arthroplasty leads to which of the following? Review Topic

QID: 4623
1

Increased strength

1%

(22/2564)

2

Increased elution of antibiotics

91%

(2328/2564)

3

Increased cement density

1%

(24/2564)

4

Improved cement-prosthesis bonding

4%

(115/2564)

5

Increased reinfection rate

3%

(66/2564)

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PREFERRED RESPONSE 2

(OBQ05.176) A 72-year-old male presents 2 years status post fixation of an impending pathologic right femur fracture due to metastatic renal cell carcinoma. He is minimally ambulatory due to pain. Despite radiation therapy, there has been progression of the lesion with extensive cortical bone loss, which is shown in Figure A. A proximal femoral replacement arthroplasty is performed without complications, and is demonstrated in Figure B. Which of the following is true regarding this patients post-operative course?
Review Topic

QID: 1062
FIGURES:
1

Deep prosthetic infection is the most common complication

49%

(408/830)

2

Mean Harris Hip score will likely not improve

5%

(43/830)

3

The patient will most likely continue to be minimally ambulatory

28%

(229/830)

4

Aseptic failure rate at 5 years is >50%

16%

(129/830)

5

Pre-operative radiation decreases the risk of infection post-operatively

2%

(14/830)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(OBQ10.147) A 65-year-old woman complains of worsening left knee pain 7 months following total knee arthroplasty. She reports good pain relief for the initial 5 months following surgery. Physical exam is notable for a stable knee with range of motion from 0-115 degrees. Radiographs are provided in Figures A and B. Which of the following is the most appropriate next step in management? Review Topic

QID: 3235
FIGURES:
1

Nuclear bone scan

0%

(10/2349)

2

One stage revision total knee arthroplasty

0%

(9/2349)

3

Knee MRI

1%

(13/2349)

4

CRP, ESR, WBC

97%

(2273/2349)

5

Physical therapy with focus on range of motion and quadriceps strengthening

2%

(38/2349)

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PREFERRED RESPONSE 4

(OBQ08.164) A 65-year-old male who had a total knee arthroplasty 8 years ago comes into the office with worsening knee pain. The orthopaedic surgeon is concerned about infection and aspirates the knee. Which of the following are the lowest laboratory values from a synovial aspirate suggestive of infection? Review Topic

QID: 550
1

WBC of 500 cells/ml and PMN 25%

1%

(16/1931)

2

WBC of 1,000 cells/ml and PMN 25%

2%

(45/1931)

3

WBC of 1,500 cells/ml and PMN 70%

85%

(1644/1931)

4

WBC of 5,000 cells/ml and PMN 70%

8%

(164/1931)

5

WBC of 25,000 cells/ml and PMN 70%

3%

(58/1931)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(OBQ11.195) A 50-year-old woman underwent cemented total knee arthroplasty 3 weeks ago. She reports that she has 1 week of drainage the size of a quarter on a gauze pad that she places over the incision three times daily. Her body mass index is 53 and her medical problems include hypertension and type 2 diabetes. Blood work shows a CRP of 1.1mg/L (normal 1-3mg/L). Knee aspiration yields WBC of 673 cells/mm(3) with 30% polymorphonucleocytes, and a negative gram stain. There is no surrounding erythema but there is a 1cm area at the inferior aspect of the wound that has a large amount of serous drainage able to be expressed. She has a painless range of motion is 0° to 117°. What would be the next most appropriate step in management? Review Topic

QID: 3618
1

Removal of all components with antibiotic spacer placement and staged revision

3%

(56/2170)

2

One-stage irrigation and debridement with removal of components to a cementless prosthesis

1%

(15/2170)

3

Empiric oral antibiotics for 4 weeks and steri-strips over the area of drainage

11%

(230/2170)

4

Surgical exploration with debridement and possible polyethylene exchange

83%

(1804/2170)

5

Bone scan and repeat aspiration with empiric intravenous antibiotics for 4 weeks

3%

(55/2170)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(OBQ11.60) A 72-year-old man reports persistent, progressively worsening pain in his hip after undergoing a total hip arthroplasty 15 months ago. A current AP hip radiograph is shown in Figure A. What is the next most appropriate step in the care of this patient? Review Topic

QID: 3483
FIGURES:
1

IV Antibiotics

0%

(6/2343)

2

Obtain serum metal ion values

1%

(23/2343)

3

Obtain ESR, CRP, and WBC

95%

(2230/2343)

4

Obtain CT and MRI of the hip

1%

(24/2343)

5

Urgent debridement and component explantation

2%

(51/2343)

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PREFERRED RESPONSE 3

(OBQ05.235) A 67-year-old diabetic male presents 4 months status post right total knee arthroplasty (TKA) complaining of pain and stiffness for the last four weeks. A clinical photograph is shown in Figure A. Radiographs and a bone scan are shown in Figures B, C and D. Blood work shows an ESR of 14mm/hr (normal 0-12mm/hr) and a CRP of 2mg/L (normal 1-3mg/L). Knee aspiration yields WBC of 1000, 30% PMNs, and a negative gram stain. He finished a 14-day course of antibiotics prescribed to him by his primary care physician one week ago. Which of the following is the most appropriate next step in management? Review Topic

QID: 1121
FIGURES:
1

Broad-spectrum, empiric oral antibiotics

2%

(19/904)

2

Repeat aspiration after one week

75%

(674/904)

3

Irrigation and debridement of the right knee with a polyethylene liner exchange

7%

(61/904)

4

One-stage irrigation and debridement of the right knee with a component exchange

4%

(35/904)

5

Two-stage component removal, antibiotic spacer placement and subsequent revision

12%

(110/904)

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PREFERRED RESPONSE 2
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