This document discusses the diagnosis and treatment of infected total knee arthroplasty. It begins by outlining the challenges and costs associated with this complication. Risk factors are then examined including patient characteristics, surgical factors, and postoperative management. Diagnostic tools are explored such as aspiration, hematologic and radiographic studies. The optimal diagnostic thresholds for various tests are provided. Microbiology patterns and differential diagnosis are covered. The document concludes by classifying infections based on timing and clinical presentation and outlining the basic treatment options.

1. Diagnosis of
Infected total knee arthroplasty
Warakorn Jingjit, MD
Orthopaedic Department, Faculty of Medicine
Chiang Mai University

2. One of the most devastating & challenging complication
Immense financial & psychological burden
Cost of treatment 15,000 - 60,000 $ / TKA
Hebert CK, CORR, 1996
Sculco TP, Orthopedics, 1995

3. Incidence
• 0.39% in primary TKA
• 0.97% in revision TKA

4. Projection of the TKA & THA number
Kurtz S, JBJS, 2008

5. Projection of the TKA & THA infection
Kurtz S, JBJS, 2007

6. Risk factors
1.
2.
3.
4.
Patient / host
Surgical environment
Surgical technique
Postoperative management

7. Risk factors
Patient / host
• Immunocompromise
•
– RA (4.4%)
– Steroid therapy
– DM (7%)
– Poor nutrition
• Albumin <3.5g/dl: 7-fold
• Lymphocyte <1,500 cells/mm3: 5-fold
•
– HIV
– Organ transplant
•
•
•
•
Hypokalemia
Tobacco use
Obesity
•
•
•
Debilitation
–
–
–
–
–
Advanced age
Alcoholism
Renal failure
Cirrhosis
Prolonged pre-op
hospitalization
Hypothyroidism
Previous surgery
Psoriasis
Previous infection
Concurrent infection

8. Risk factors
Surgical environment
• Personnel
• Clean air
Laminar air flow, UV light
• Surgical attire
• Operative site preparation
Ritter MA, CORR,1988
Ritter MA, Orthop Clin North Am,1989
Berg M, JBJS (Br), 1991
Ritter MA, CORR, 1999
Peersman G, CORR, 2001

9. Risk factors
Surgical technique
•
Surgical time
Operative time > 2.5 hrs
Peersman, CORR, 2001

10. Risk factors
Surgical technique
Prophylactic antibiotic
Single most effective method of ↓ infection
1st gen. cephalosporin
Allergy  vancomycin / clindamycin
30-60 min before incision
(peak serum bone conc. within 20 min)
 Repeat every 4 hrs & bleed >1,000 ml
 Discontinue 24 hrs after surgery





11. Risk factors
Surgical technique
Prophylactic antibiotic bone cement
•
High risk 1o TKA, revision TKA

12. Risk factors
Surgical technique
Implant
• Hinged prosthesis
• Infection rate at 10 yrs ~ 15%
• Bengtson S, Acta Orthop Scand, 1991
• Hanssen AD, CORR, 1995
• Schoifet SD, JBJS, 1990

13. Risk factors
Post operative management
• Bacteremia: oral > GI > GU procedure
• Avoid in first 3-6 mo (high incidence)
AAOS & ADA 1997
• First 2 yrs, specific risk factor for all pts  ATB prophylaxis
• After 2 yrs  consider in high risk pts
Recommended regimens (before procedure 1 hr)
• Cephalexin, cephradine, amoxicillin 2 g. oral
• Cephalosporin 1 g / ampicillin 2 gm IV / IM
• Clindamycin 600 mg oral (allergy to penicillin)
• Clindamycin 600 mg IV / IM (allergy to penicillin)
Advisory statement. J Am Dent Assoc, 1997

14. Potential risks of hematojenous
total joint infection
• All patients for the first 2 years after joint replacement
• lmmunocompromised / immunosuppressed patients
- Inflammatory arthropathies
- Drug-induced immunosuppression
- Rheumatoid arthritis
- Radiation-induced immunosuppression
- Systemic lupus erythematosus
• Patients with comorbidity conditions
- Previous prosthetic joint infections - HIV infection
- Poor nutrition
- Insulin-dependent diabetes
- Hemophilia
- Malignancy
Advisory statement. J Am Dent Assoc, 1997

15. Microbiology
Predominant organisms
Goldman RT, CORR, 1996

16. Microbiology
• Fungal infection = rare
 Candida = predominant
• Mycobacterium tuberculosis = rare

17. Microbiology
• Mucopolysaccharide biofilm
• Protect from antibodies, phagocytes, ATB.,
• ↑ virulence

18. Microbiology
• Methicillin-resistant organism  vancomycin
Ries MD, J Arthroplasty, 2001
• Rifampicin = good biofilm & tissue penetration
 improve success when use ĉ other synergistic agent
Zimmerli W, JAMA, 1998

19. Differential diagnosis
A painful knee is infected until proved otherwise
Insall, 1981
•
•
•
•
Periprosthetic fx
PF problem
Aseptic loosening
Soft tissue disruption
•
•
•
•
Instability
RSD
HO
Arthrofibrosis

20. Diagnosis
Fundamental of diagnosis
* * * High index of suspicion * * *
Clinical history Physical examination Radiography Aspiration Hematologic
studies
Radionuclide studies
Pathology

21. Diagnosis
History
• Pain = most common presenting symptom
• Typical = rest / night / persistent / progressive pain
• Progressive stiffness
• Hx of prolong postop drainage, ATB treatment
Physical examination
• Swelling, effusion, warmth, erythema, tenderness
• Painful range of motion
• Persistent wound drainage
 strongly suggestion  early aggressive Rx

22. Diagnosis
• Swab wound  not recommend
• Empirical ABO for wound drainage  mask symptoms,
affect subsequent C/S, predispose for drug resistant
• Diagnosis in early postop period
– ESR, CRP  limit value
– Typically by arthrocentesis

23. Aspiration
• Leucocyte count & differentiation
• Gram strain (sens 97%, spec 26%) (
• Culture for aerobic & anarobic bacteria
>1,700/ml3, PMN > 65% (sens 94-97%, spec 88-98%)
Trampuz A, Am J Med, 2004
• Ongoing ATB  stop for several wks before aspiration

24. Mark Coventry Award Paper
Diagnosis of early post-operative infection following TKA:
The utility of synovial fluid cell count and differential
“Synovial WBC count is an excellent test for diagnosing
infection within 6 wks after 1oTKA
with an optimal cut-off 27,800 cells/mm3 and 89% PMN”
Sens 84%, spec 99%, PPV 94%, NPV 98%
Craig J. Della Valle
Presented at the Knee Society Specialty Day Meeting
March 13, 2010, New Orleans

25. Hematologic studies
For chronic infection
ESR
– Positive > 30 mm/hr (sens 80%, spec 62.5% )
– False positive: infection elsewhere, inflammation,
CNT dis, neoplasm, recent operation (< 3 mo)
– False negative: prior antibiotics
CRP
– Positive > 10 mg/L (sens & spec 85%)
– Return to normal within 3 wks after operation
ESR + CRP: PPV 83%, NPV 100%
Barrack RL, CORR, 1997
Swanson KC, The adult knee, 2003

26. Guideline for ESR & CRP
1. Normal ESR & CRP reliable for the absence of infection
2. CRP more useful than ESR for monitoring
3. Use with other tests for the diagnosis of infection
Spangehl MJ, JBJS, 1999

27. PCR
•
•
•
•
•
Molecular genetic diagnosis
Identify 16S RNA gene
Expensive
Time-dependent
False positive
Remain experimental modality !!!
Mariani BD, CORR, 1996

28. X-ray
Sequential plain radiographs
• Progressive radiolucencies
• Focal osteopenia / osteolysis of subchondral bone
• Periosteal new bone formation
Morrey BF, CORR, 1989
• Bone destruction – infection present > 10-21 days
• Lytic lesion – destroy 30-50% of bony matrix
Early infection – no abnormal finding !!!

29. Radioisotope scan
Occasionally helpful in chronic infection
• Tc-99m MDP
• In-111 leukocyte scan
• Tc-99m sulfur colloid

30. Radioisotope scan
Occasionally helpful in chronic infection
Isotope
Sensitivity Specificity Accuracy
Tc 99m
95%
20%
54%
Indium 111
77%
75%
90%
Tc 99m + In111
100%
97%
97%
Palestro CJ, Radiology, 1991

31. Intraoperative tissue frozen section
• Widely use
• Result depend on
 Adequate & representative tissue obtaining
 Accurate interpretation by skilled pathologist
> 5 PMN/HPF at least 5 fields  Sens 100%, spec 96%
>10 PMN/HPF at least 5 fields  Sens 25%, spec 98%
Feldman DS, JBJS, 1995
Della Valle CJ, JBJS 1999

32. Intraoperative tissue frozen section
Reliable predictor for infection
• >10 PMN/HPF: sens 84%, spec 99%, PPV 89%, NPV 98%
• 5-10 PMN/HPF: need other test to differentiate
• <5 PMN/HPF: infection was highly unlikely
Lonner Jh et al, JBJS,1996

33. Intraoperative gram strain
• Unreliable
• Low sensitivity = 0-14.7%
Atkins BL, J Clin Microbiol, 1998
Della Valle CJ, J Arthroplasty, 1999

34. Intraoperative culture
Gold standard
Sample: fluid & tissue
 Joint capsule
 Synovial lining
 IM tissue
 Granulation tissue
 Bone fragments
• False +ve: contamination
• False -ve: prior ATB, transport system, lab
- Duff GP, CORR, 1996
- Bauer TW, JBJS, 2006

35. Definite diagnosis
At least one of the following
1. Same organism from c/s ≥ 2 specimens by aspiration /
deep tissue from surgery
2. Intraarticular tissue histopathology = acute inflammation
3. Gross purulence at the time of surgery
4. Actively discharging sinus tract
Hansen, CORR, 1994

36. Definite diagnosis
At least one of the following
1. Open wound / sinus tract communicate ĉ joint
2. Systemic signs / symptoms ĉ pain & purulent fluid
3. At least 3 of 5
 ESR > 30 mm/hr
 CRP >10 mg/L
 Frozen section > 5 PMN/HPF
 Preoperative aspiration c/s ≥ 1 +ve
 Intraoperative c/s ≥ 1 +ve
Spangehl MJ, JBJS, 1999

38. Segawa &Tsukayama classification
“Classify on the basis of clinical presentation”
Type1
Timing
Definition
Type2
Type3
Type4
Positive
intraop C/S
Early
postoperative
infection
Acute
hematogenous
infection
Late (chronic)
infection
Same
Occurring within
organism
first month after
≥2 from C/S
surgery
Hematogenous
Chronic
seeding of
indolent
previously
clinical course;
well-functioning
present >1
prosthesis
month
* * * Guide to treatment * * *

39. Treatment
Basic treatment options
1.
2.
3.
4.
5.
6.
Antibiotic suppression
Debridement ĉ prosthesis retention
Resection arthroplasty
Arthrodesis
Amputation
Reimplantation - one / two stage