Infected TKA, and joint infection of knee

1. INFECTED TOTAL
KNEE
ARTHROPLASTY

2. INTRODUCTION
Arthroplasty is the surgical reconstruction of a joint
which aims to relieve pain,correct deformities and
retain movements of a joint.
Total Knee Arthroplasty (TKA) is the surgical
procedure to replace the weight bearing surfaces
of the knee joint.

3. EVOLUTION OF TKA
● Fergussen (1860) – Resection arthroplasty
● Verneuil – First interposition arthroplasty
● 1940 – First artificial implants were tried when
molds were fitted into femoral condyle
● 1950 – Combined femoral and tibial articular
surface replacement appeared as simple hinges

4. ● Frank Gunston (1971) – Developed metal on
plastic knee replacement
● John Insall (1973) – Designed what has
become prototype of current total knee
replacements. Prothesis made of three
components which would resurface all 3
surfaces of knee – the femur,tibia and patella

5. Indications of TKR
● Relieve pain caused by severe osteoarthritis
with or without significant deformity
● Indicated in older patients with more sedentary
lifestyles
● Young patients with significant functional
impairment from OA or other systemic arthritis
or osteonecrosis with subchondral collapse of
femoral condyle
● Severe pain from chondrocalcinosis and
pseudogout in elderly

6. Contraindications
● Recent/ current knee sepsis
● Remote source of ongoing infection
● Extensor mechanism discontinuity/ severe
dysfunction
● Recurvatum deformity secondary to
neuromuscular weakness
● Presence of painless, well functioning knee
arthrodesis

7. Designs of Implants
● Unconstrained
○ Cruciate retaining
○ Cruciate substituting
○ Mobile bearing
knees
● Constrained (Hinged)
● Unicondylar prosthesis
● Total condylar
prosthesis

8. Cruciate retaining
Advantages :
● More closely resembles
knee kinematics
● Bone preserving
● Improved proprioception
● Avoids post cam
impingement /
dislocation
Disadvantages :
● Tight PCL – Increased
poly wear
● Rupture PCL – Flexion
instability
Intact PCL
Varus <10 , Valgus >15

9. Cruciate stabilized
Advantages :
● Easier to balance knee
● More range of motion
Disadvantages :
● Cam Jump
● Post wear
● Patellar clunk syndrome
● Additional cut from distal
femur
Absolute indications :
● Previous patellectomy
● Inflammatory arthritis
● Deficient PCL
Cam and post mechanism
Insert more congruent/ dished

10. Mobile Bearing Design
● Poly rotates over tibial
base plate
● Reduced poly wear
● Bearing spin out

11. Constrained (Hinged) Design
● Linked femoral and tibial
components
● Tibial bearing rotates
around yoke
Disadvantages :
● Aseptic loosening
● Large amount of bone
resection
Indications :
● Global ligamentous
deficiency
● Hyperextension
instability

12. Unicondylar TKR
Advantages :
● Shorter rehabilitation
time
● Greater average post op
range of motion
● Preservation of
proprioception and
function of cruciate
ligaments
Contraindications :
● Inflammatory conditions
● Damage to articular
cartilage
● Flexion contracture >5
● Preoperative ROM <90
● Angular deformity >15
● ACL deficiency

13. Total Knee Replacement Today
Majority of TKR today are condylar
replacements which consist of :
● Cobalt-chrome alloy femoral component
● Cobalt-chrome alloy or titanium tibial
tray
● UHMWPE tibial bearing component
● UHMWPE patellar component

14. Procedure

15. Computer assisted TKA
● Optical localization using infra-
red light is currently the most
widely used method of
communication
● The tracking markers attached to
surgical instruments and
reference frames attached to
bony landmarks have light
emitting diodes (LED) which
send out light pulses to a camera
(optical localizer).

16. ● Once the skin incision is made
and the distal femur and proximal
tibia are exposed, the anatomic
landmarks critical for CAS
guided navigation are located
using probe
● The centre of the femoral head,
knee and ankle joints are
determined using a kinematic
registration technique
● Femoral and tibia resections to be
done are guided by computer
interface.

17. ● The system can be used to guide the release of tight
soft tissues medially, laterally and posteriorly if this is
necessary to establish a balanced, well-aligned knee.
● After the actual implants are inserted, the navigation
system is used to measure the final frontal and sagittal
alignment of the extremity, the final medial-lateral
stability and final range of motion.

18. Robotic TKA
● Robotic TKR uses a preoperative CT scan to create a 3D
reconstruction of the original knee. This patient model is
then used to calculate the measurement of the femoral and
tibial bone resection and select the exact size of
the implant.
● Indications :
○ Longer prosthesis lifespan because of bone
preparation accuracy
○ Adequate restoration of mechanical axis
● Contraindications :
○ Increased surgical time – Risk factor for SSI

19. Types of robotic TKR
● Robotic arm with haptic
interface :
○ Semiactive, stops the saw
when bone resection begins
to go outside predetermined
parameters.
● Handheld robotic burr :
○ Semiactive, follows the
navigation field’s burring tool
trajectory which controls
exposure and speed of burr
to protect against undesired
resection

20. ● CT based autonomous active
system :
○ The CT scan is uploaded to
software to create a three-
dimensional image, then the
surgeon plant the
surgery preoperatively and decide
the exact resection size of the
bone, prosthesis sizing, and
positioning.
● Motor-powered robotic TKR :
○ It needs a preoperative plan to
avoid mistakes while using a
conventional saw, oscillating to
ensure accurate alignment and
positioning of the prosthesis

21. Pitfalls :
● Expensive
● Needs software applications to be installed
● Increased time of operation
● Any unresolved difficulties require conversion to
conventional TKR

22. Complications
● Thromboembolism
● Infection
● Patellofemoral complications
○ Patellofemoral instability
○ Patellar fractures
○ Patellar component loosening/ failure
○ Patellar clunk syndrome
○ Extensor mechanism failure
● Neurovascular complications
● Periprosthetic fractures

23. “
PERIPROSTHETIC JOINT
INFECTION

24. Introduction
● Most dreaded complication affecting TKA
patients
● Incidence : 2-3%
● Due to higher life expectancy, lifestyle changes
in increasingly elderly populations and more
expectations for mobility in older age, the
number of implanted prosthetic joints continues
to rise.
● With a steadily increasing number of
implantations, the number of PJI cases also
rises continuously.

25. ● Longer prosthesis indwelling time is associated
with a higher cumulative risk for
haematogenous infections during the entire
implant lifetime.
● Development of modern detection methods for
microbial biofilms helps to recognize chronic
infections also.
● Management of PJI requires complex treatment
strategies including multiple surgical revisions
and long-term antimicrobial treatment.

26. ● An accurate diagnosis with identification of the
infecting micro-organism(s) and its antimicrobial
susceptibility is important for choosing the most
appropriate treatment strategy to eradicate the
infection.
● When missed or undertreated, PJI leads to
persistence of infection and multiple surgical
revisions causing poor function or disability,
considerably impairing quality of life

27. Pathogenesis
● Two thirds of cases are caused through
intraoperative inoculation of microorganisms
● Depending on microbial virulence, PJI can
manifest either early (within 4 weeks after
implantation) or with a delay (between 3 months
and 3 years)
● Patients present typically with acute onset of
clinical symptoms after a painless post-
operative period.

28. ● The search for and the elimination of the
primary focus is necessary in preventing
infection relapse.
● The most common primary foci are :
○ Skin and soft tissue infections : Staphlococcus
aureus
○ Respiratory tract infections : Streptococcus
pneumoniae
○ Gastrointestinal infections : Salmonella, Bacteroides,
Streptococcus gallolyticus
○ Urinary tract infections : E.coli,Klebsiella,
Enterobacter species
○ Stretococcus viridans – During dental procedures
○ Staphylococcus epidermidis – Infected intravascular
devices

29. ● Direct spread of infection (per continuitatem)
occurs through direct contact between
prosthesis and outer environement (Open
periprosthetic fracture) or as a spread from
nearby infectious focus (soft tissue
infection,osteomyelitis)

30. Role of microbial biofilm
● The ability to grow and persist on the implant
surface and on necrotic tissue in the form of a
biofilm represents a basic survival mechanism
by which micro-organisms resist environmental
factors.
● After the first contact with the implant, micro-
organisms immediately adhere to its surface.
● In the first hours after the adhesion multilayer
cellular proliferation, as well as cell-to-cell
adhesion, lead to formation of micro-colonies
and to initial growth of biofilm.

31. ● Mature biofilms take four weeks to develop and
represent complex 3D-communities where
micro-organisms of one or several species live
clustered together in a highly hydrated, self-
produced extracellular matrix (slime).
● Depletion of metabolic substances and waste
product accumulation cause micro-organisms to
enter a slow- or non-growing (stationary) state.
● Planktonic bacteria can detach at any time,
activating the host immune system, causing
inflammation, oedema, pain and early implant
loosening

32. ● The presence of a foreign body reduces the
minimal infecting dose of S. aureus more than
100,000-fold.
● This is caused by a locally acquired immune
defect, as granulocytes show decreased
phagocytic activity (the so-called frustrated
phagocytosis).
● Activation of granulocytes on foreign surfaces
leads to the release of human neutrophil
peptides (defensins) that deactivate the
granulocytes.

33. Definition

34. Risk factors
Patient dependent factors
● Nutrition
● Immunologic status
● Alcohol abuse
● Smoking
● Infection at remote site
● Congestive heart failure
● Depression and other
comorbidities
Surgeon dependent factors
● Prophylactic antibiotics
● Skin and wound care
● Operating environment
● Surgical technique
● Treatment of impending
infections as in open
fractures

35. ● Diabetes :
○ Hyperglycemia even in non diabetic patients is a risk
factor for developing PJI. A glucose level greater than
200mg/dl requires treatment before elective surgery
● Rheumatoid arthritis
○ Incidence of PJI is 1.6 times higher in patients with
RA compared to osteoarthritis, could be due to use of
disease modifying antirheumatic drugs.
○ It is recommended that these medications be
discontinued according to their half-life and resumed
2 weeks postoperatively

37. Classification

38. Diagnosis
● Clinical signs :
Acute infection :
○ Systemic – fever
○ Local – Pain,erythema,oedema,prolonged
post-operative wound effusion or
dehiscence,impaired joint function
Chronic infection :
○ Clinically difficult to distinguish from aseptic
failure

39. ● The only definitive clinical signs confirming
infection are the presence of a sinus tract or
visible purulence around the prosthesis

40. ● Imaging studies :
Radiographs –
○ Examination of serial
conventional radiographs may
be helpful to detect early
loosening.
○ A rapid development of a
continuous radiolucent line of
greater than 2 mm or focal
osteolysis within the first three
years after implantation are very
suggestive of an infection but
are neither sensitive nor specific
enough to distinguish between
septic and aseptic failure.

41. Computed tomography (CT) –
○ Gives good contrast resolution of bone and
surrounding soft tissue and can be useful in pre-
operative evaluation of excessive bone defects

42. Magnetic resonance imaging (MRI)
○ Displays greater resolution for soft tissue
abnormalities than CT.
○ In particular, metal artefact reduction sequence
(MARS) MRI is useful for differential diagnosis with
metallosis
Periprosthetic joint infection after TKA in 60 year old man.
Axial,sagittal,axial STIR MR images with thickening,layering or signal
hyperintensity of synovium with expansion of joint capsule

43. ● Bone Scintigraphy:
○ 99mTc has an excellent sensitivity but
specificity to diagnose PJI is low
○ Positive uptake detected by delayed
phase imaging due to increased bone
remodelling around the prosthesis is
normal in first two years
○ Use of anti-granulocyte scintigraphy
with 99mTc-labelled monoclonal
antibodies demonstrates sensitivity of
83% and specificity 79%
○ Scintigraphy with Indium-111-labeled
leukocytes in combination with
marrow imaging shows 90%
accuracy.

44. Laboratory studies :
○ WBC count, ESR,CRP or Procalcitonin – none of
them have sufficient sensitivity or specificity to
diagnose or exclude PJI.
○ CRP - Serial measurements over time are needed for
accurate interpretation

45. ● Synovial fluid analysis
○ Pre-operative joint aspiration is the most valuable
diagnostic tool and should be performed for every
painful prosthetic joint prior to the surgical revision
○ Determination of synovial fluid leukocyte count and
percentage of granulocytes represents a simple,
rapid and accurate test for differentiating between
PJI and aseptic failure.
○ Synovial fluid culture : sensitivity : 45-75% ,
specificity : 95%

46. ● Alpha defensin
○ Antimicrobial peptide released by activated
neutrophils as a response to bacterial infection that
has been used as a biomarker for detection of PJI.
○ The Alpha Defensin Lateral Flow (ADLF) test is a
qualitative test that determines the presence of alpha
defensin in synovial fluid and can be performed in the
operation theatre or immediately after the joint
aspiration within 10 minutes.
○ In the early post-operative period when synovial fluid
leukocyte count is not readable (specificity of only
60% in the first six weeks post-operatively), the ADLF
test may still be applied with a specificity of 99%

47. ● Intra-operative tissue samples
○ As a general principal, three to five intra-operative
tissue samples should be submitted for the culture.
○ The sensitivity ranges between 65% to 94%

48. ● Sonication of removed implants
○ Sonication is a method using low-frequency
ultrasound waves that pass through a liquid
surrounding the prosthesis and detach biofilm micro-
organisms from the surface.
○ The sonicate fluid can then be submitted for culture
and plated onto aerobic and anaerobic plates.
○ Inoculation in the blood culture bottles improves the
sensitivity and may reduce the cultivation time by up
to five days.
○ A cut-off of 50 colony-forming units (CFU)/ml of
sonication fluid yields a sensitivity of 79% and a
specificity of 99% for the diagnosis of PJI.

49. ● Molecular methods
○ Polymerase chain reaction (PCR) can identify
pathogens in synovial fluid with a sensitivity and
specificity of 84% and 89%, in sonication fluid of 81%
and 96%and also has high sensitivity and specificity
in patients on antibiotics

50. ● Histopathological examination
○ Histopathology of periprosthetic tissue should be
considered a standard procedure in the diagnosis of
PJI.
○ Neutrophil granulocytes can be detected through
immuno-histochemical techniques and validated
using histopathological scores.
○ The presence of PJI can be determined by the count
of neutrophils per high-power field at a magnification
of 400.
○ The definition of acute inflammation has been
variable proposed from ⩾ 1 to ⩾ 10 neutrophils per
high-power field.

51. Treatment options
● Antibiotic suppression
● Debridement with prosthesis retention
● Resection arthroplasty
● Knee arthrodesis
● One-stage or two-stage reimplantation
● Amputation
The choice between the various options depends on the
general medical condition of the patient, the infecting
organism, timing and extent of infection, the residual usable
bone stock, status of the soft-tissue envelope, and extensor
mechanism continuity.

52. ● Antibiotic suppression:
Indications :
○ Only when prosthesis removal is not feasible
○ Infecting microorganism is of low virulence and
susceptible to oral antibiotic of low toxicity
Suppression must be lifelong and limited to patients in
whom no other more successful treatment options are
available
Risks :
○ Development of resistant strains of bacteria
○ Progressive loosening
○ Extensive infection
○ Septicemia

53. ● Because the most common organisms causing
postoperative infection are Staphylococcus aureus,
Staphylococcus epidermidis, and Streptococcus species,
the usual choice of prophylactic antibiotic is a first-
generation cephalosporin, such as cefazolin.
● In patients with significant penicillin allergy, vancomycin
or clindamycin may be used.

56. Joint debridement with prosthesis
retention
● Limitations :
○ Early postoperative infection
○ Acute hemtogenous infection with well-fixed
prosthesis
● Contraindication :
○ Late chronic infection
○ Infection with S.aureus
● Debridement,Antibiotics,Implant retention (DAIR) –
Radical debridement of all necrotic
tissues,synovectomy,excision of sinus tracts and
thorough irrigation with copious volumes of sterile saline
is perfomed, combined with replacement of
mobile,exchangable prosthetic parts

57. Resection arthroplasty
● Removal of the infected
prosthesis and cement and
debridement of the synovium.
● The bone ends can be
temporarily apposed with heavy
sutures or pins and leg is
maintained in a cast for 6
months.
● Ideal for a patient with infected
TKA and severe polyarticular RA
with limited ambulation

58. Knee Arthrodesis
● Provides stable,generally painless limb
● Indications :
○ High functional demands
○ Disease involving single joint
○ Young age
○ Deficient extensor mechanism
○ Poor soft tissue coverage
○ Immunocompromised patient
○ Infection with highly virulent microorganism
● Contraindications :
○ Ipsilateral hip or ankle arthritis
○ Contralateral knee arthritis or limb amputation
○ Severe segmental bone loss

59. Exchange arthroplasty
● Offers the greatest chance of functional knee recovery
after an infected TKA
● One-stage exchange arthroplasty is performed essentially
as a revision arthroplasty with an emphasis on
debridement and surgically rendering the wound as close
to sterile as possible. The reported success rate of one-
stage exchange is approximately 89%.
● More commonly, exchange arthroplasty is done in two
stages: initial prosthesis removal and debridement
followed by a period of intravenous antibiotics and later
reimplantation. Success rates are 89% to 100%

60. ● Antibiotic-impregnated PMMA
spacers are used by many
surgeons to maintain soft-tissue
tension of the knee during the
interval between debridement
and reimplantation in two-stage
procedures
● Articulating spacers with
temporary prosthetic
components have been
advocated for two-stage
exchange to improve range of
motion, maintain functional
status of the limb during
treatment, and minimize bone
loss between stages.

61. Local antimicrobials in bone cement

62. Amputation
● Last option for treatment of infected TKA – Above knee
amputation
● Indicated only in life threatening infection or persistent
local infection with massive bone loss not suitable for
arthrodesis or resection arthroplasty

63. Treatment algorithm

65. TB and Prosthetic joint infection
● The majority of TBPJIs occur within the first two years
after surgery, 25% of all TBPJIs occur after two years
from primary procedure
Divided into 3 sources :
1. Recurrence of previous tuberculosis infection in a
native or postoperative knee
2. Dissemination of tuberculosis from the original
source in the lungs or extrapulmonary source
3. Reactivation of latent tuberculosis infection

66. Treatment strategy
● Key principles are source control, anti-tuberculosis
medications, and early diagnosis and treatment, or
empiric therapy in cases when a diagnosis might be
delayed.
● Anti tubercular medical therapy :
○ 2 months HRZE + 6-9 months HR
○ Requires not only rapid diagnosis but also no other
sites of infection,prosthetic loosening or osteolysis

67. ● Anti-tuberculosis Medical Therapy, Joint Incision and
Drainage (I&D), and Preservation of Prosthesis :
Limited to the following clinical situations:
(1) early-onset infection
(2) clinical and imaging findings consistent with an
absence of prosthetic loosening
(3) sensitivity to anti-tuberculosis medications

68. ● Anti-tuberculosis Medical Therapy, Joint I&D,
and Two-Stage Replacement Arthroplasty
○ Nearly all late-onset TBPJI, severe suppurative
infections, active sinus tract formation, signs of
periprosthetic osteolysis or prosthetic loosening,
should undergo a two-stage replacement
arthroplasty, as results have been shown to be as
effective as 90%
○ Patients must be medically fit for multiple surgeries
and have adequate bone stock, but this two-stage
revision remains the gold standard for a late-onset
joint infection following arthroplasty

69. ● Anti-tuberculosis Treatment, Removal of
Prosthesis and Arthrodesis
○ Knee arthrodesis is a procedure resulting in severe
limitation of functionality and quality of life.
○ While arthrodesis is not a first-line treatment option, it
can be a useful option for patients with persistent
infection and medical comorbidities limiting the ability
to tolerate multiple procedures

70. Prevention of PJI