Diagnosis and Treatment of Infection Following Total Hip Arthroplasty

1
Diagnosis and Treatment of Infection Following
Total Hip Arthroplasty

• ICL 34 35

2
Introduction

• In the 1960s, Charnley reported a rate of
  infection of 9.5.
• More recently, authors have reported that
  infection causes failure after 1-2 of primary
  THAs.
• In the US, the cost per year to treat the
  3,500-4,000 infections following THA is between
  150 and 200 million dollars.

3
Introduction

• Infection following THA can present a diagnostic
  challenge
• No test is 100 sensitive and 100 specific.
• The diagnosis then relies heavily upon the
  surgeons judgement of the clinical presentation,
  the findings on PE, and the interpretation of the
  results of previous investigations. Misdiagnosis
  can be critical.

4
Clinical Presentation

• A thorough HP are of paramount importance in the
  Dx of infection.
• Coventry and later Fitzgerald and assoc.
  described the most common system for the
  classification of infection after THA.
• Type-I
• Type-II
• Type-III

5
Type-I Infections

• These occur immediately in the postop
  period--usually during the first month.
• Systemic signs include fever, chills, sweating,
  and continuous pain.
• Wound appears erythematous, swollen, fluctuant,
  and tender, and if drainage is present it is
  usually purulent.
• Caused by infected hematomas or superficial
  wounds spreading below the fascia.

6
Type-II Infections

• These are also believed to begin at the time of
  surgery.
• Usually seen between 6 and 24 months after
  procedure
• Hallmark is a gradual deterioration in function
  and an increase in pain.
• Often, the only clue to infection is early
  loosening of the components.
• Systemic Sxs are not part of the presentation.

7
Type-III Infections

• These are the least common and are caused by a
  hematogenous spread to a previously asymptomatic
  hip, usually 2 years or more after arthroplasty.
• Generally, there is an acute febrile episode
  followed by a sudden , rapid deterioration of the
  hip.
• Dx can usually be made on the basis of the HP.

8
Type-III Infections

• These are likely to occur in patients who are
  immunosuppressed, have recurrent bacteremia, such
  as IVDAs, or those who need repeat urinary
  catheterization.
• Other factors with type-III are dental
  manipulation, respiratory infections, open skin
  lesions, and endoscopy.

9
Preoperative Investigations

• White Blood-Cell Count
• Erythrocyte Sedimentation Rate
• C-Reactive Protein Level
• Plain Radiography
• Radionuclide imaging
• Other Imaging Modalities
• Hip Joint Aspiration
• Molecular Analysis

10
White Blood-Cell Count

• WBC is rarely abnormal in patients who have
  infection following THA--studies show
  approximately 15.
• If the patient does have an abnormal count, the
  systemic infection is usually clinically obvious
  and is either type-I or type-III.

11
Erythrocyte Sedimentation Rate and C-Reactive
Protein Level

• The ESR and the CRP level are the most useful
  screening labs for the diagnosis of a potential
  infection following THA.
• RBCs have negative charges and acute phase
  reactants have positive charges.
• An elevated ESR is an indirect indicator of an
  abundance of acute-phase reactants.
• Values of gt 30 or 35 mm /hour are generally
  considered to be abnormal.

12
C-Reative Protein Levels

• Synthesized in the liver and is found only in
  trace amounts under normal conditions.
• It rises in a nonspecific manner as a result of
  infectious, inflammatory, or neoplastic
  disorders.
• It reaches its maximum values within 48 hours
  after surgery, then returns to trace amounts in
  aprox. 2-3 weeks. Therefore, it is a more
  sensitive indicator of infection.

13
Plain Radiography

• Plain radiographs should be made for all patients
  who have a failed arthroplasty, even though they
  are of limited value as an investigative tool for
  the dx of infection.
• Many radiographic findings are found in both
  septic and aseptic failure.
• Periosteal new bone formation, with/without
  loosening of a component, has been considered
  pathognomonic of deep infection.

14
Plain Radiography

• Early loosening and rapidly progressive
  radiolucent lines are also suggestive of
  infection.
• Evidence of loosening of the femoral component
  involves radiolucency along the stem-cement
  interface, fracture of the cement mantle or the
  stem, or migration of the prosthesis.

15
Plain Radiography

• Acetabular loosening is indicated by migration of
  the socket or the cement mantle, protrusio
  acetabuli, or acetabular fracture.
• Athrography can improve the accuracy in
  diagnosing loosening especially on the acetabular
  side.

16
Radionuclide Imaging

• Technetium-99m bone scans are sensitive but not
  specific.
• A negative bone scan can rule out infection.
• Many conditions can result in increased uptake
  for as long as one year after an uncomplicated
  THA and as long as 2 years after insertion of a
  prosthesis without cement.

17
Radionuclide Imaging

• Gallium-67 citrate is an isotope that accumulates
  in areas of inflammation.
• It is also non-specific as any process resulting
  in reactive bone formation may cause increased
  uptake.
• Indium-111-labeled white blood cells are useful
  for the dx of conditions of increased vascularity
  and white blood-cell uptake. This has been used
  in combination with technetium and had higher
  sensitivities and specificities.

18
Radionuclide Imaging

• Radiolabeled immunoglobulin-G has been used for
  the investigation of musculoskeletal infections.
• One advantage is that the patient does not have
  to have phlebotomy before the scan is made.
• Until additional studies are performed, the
  routine use of In-IgG scans cannot be recommended.

19
Radionuclide Imaging

• Currently, the use of sequential Tc-99 and
  In-111-WBC scans is being recommended, however,
  the use of radiolabeled IgG may supersede the use
  of sequential scans provided they prove to be
  superior for the dx of infection in THA.

20
Other Imaging Modalities

• MRI can be of value after an infection has been
  diagnosed . MRI can be used to determine the
  extent of the cement mantle within the femur and
  the pelvis so that the revision procedure can be
  planned appropriately.
• Ultrasound can be used to measure the thickness
  of the joint capsule, which indicates infection.
  Also soft -tissue abscesses can be evaluated.

21
Hip Joint Aspiration

• This is perhaps the most useful investigative
  tool for definitive confirmation of the presence
  or absence of infection.
• Now most authors favor a more limited role, with
  aspiration being used to confirm a clinical
  suspicion of infection.
• It can also support or negate the findings of
  other labs such as ESR and CRP that may be
  falsely elevated in connective-tissue dx.

22
Aspiration

• An additional benefit is the ability to identify
  the organism and its antibiotic-sensitivity
  profile, which may influence preoperative
  planning.
• The reported rates of sensitivity and specificity
  have varied widely. This suggests that
  aspiration is better for ruling infection in than
  for ruling it out.
• All ABX should be discontinued for 2-3 weeks
  before the aspiration.

23
Aspiration

• Local anesthetics should be used only for the
  skin and not in the joint as they are
  bacteriostatic.
• Three samples are taken and if all three are
  positive a dx of infection is made.

24
Intraoperative Investigations

• Intraoperative Frozen Sections--if ten or greater
  PMNs are found in the high-power field, this is
  evidence of a probable infection.
• Gram Stain--these may be specific, but it lacks
  any acceptable level of sensitivity.

25
Intraoperative Cultures

• Preoperative Abx should be withheld until
  specimens have been obtained
• Clean instruments that have not been used on the
  skin should be used to obtain the specimens.
• Samples should be taken close to the prosthesis
  and from inflamed tissue.
• A minimum of three tissue specimens should be
  sent fresh for immediate processing.

26
Molecular Analysis

• Molecular technology may be used to diagnose the
  presence of bacterial DNA and RNA.
• Polymerase Chain Reaction (PCR) enables to
  production of large amounts of specific sequences
  of target DNA from small quantities of starting
  material.
• It is susceptible to contamination because of its
  extremely high sensitivity to any bacterial
  particles.

27
Protocol for the DX of Infection

• Following a careful HP, both the ESR and CRP
  level should be determined.
• If both results are normal and there is no
  suggestion of infection clinically, no additional
  investigations are needed.
• If the ESR or CRP level is elevated for any
  reason or there is clinical suspicion of
  infection, then an aspiration of the hip joint
  should be performed.

28
Protocol--continued

• A dx is made if the clinical suspicion in high
  the ESR or the CRP level, or both, are elevated
  for no other known reason and the cultures of
  the aspirated fluid are positive.
• If the ESR or the CRP level, or both, are falsely
  elevated, an intraoperative frozen section may be
  used to confirm the dx.
• A sequential indium bone scan may be used
  preoperatively if the frozen section will not be
  available.

29
Conclusion

• The single most important factor in determining
  the treatment options for a patient in whom a THA
  has failed is the exclusion of a dx of infection.

30
Treatment of Infection at the Site of THA

• It is estimated that 200,000 THA will be
  performed this year in the US and that more than
  4,000 new cases of periprosthetic hip infections
  will need treatment.
• There are considerable financial implications
  also involved in revision THA.
• A longer stay in the hospital, longer OR time,
  greater blood loss, higher rate of complications,
  as well as a higher cost of the implants. It is
  estimated that the cost of tx of an infected THA
  is 50,000.

31
Surgical Treatment Options for Infected Total Hip
Prosthesis

• Debridement with retention of the prosthesis
• An immediate one-stage exchange arthroplasty
• An excision arthroplasty-either as a definitive,
  permanent procedure or as the first of a two or
  even three-stage reconstructive procedure.

32
Antibiotic Usage

• Antibiotics may be used as an adjunct to surgery
  either systemically or locally ( with the use of
  bone cement as the vehicle), or both.
• They may be used either to eradicate the
  infection or to chronically suppress the
  infection without surgical intervention.

33
Microbiologic Considerations

• Staphylococcus aureus and Staphylococcus
  epidermidis are the most common infecting
  organisms. These are followed by a wide range of
  gram- positive and gram negative bacteria.
• More than 95 of the S aureus are sensitive to
  oxacillin and therefore a cephalosporin, however,
  S epidermidis has up to a 30 resistance to
  oxacillin.

34
Micro Considerations

• Recent attention has been focused on the ability
  of an infecting organism to produce a slime
  layer, or glycocalyx. This layer takes time to
  form.
• Bacteria that exist within this biofilm are at
  least 500 times more resistant to antibiotics
  than the planktonic forms. They are also
  resistant to complement activation and neutrophil
  injestion.

35
Surgical Considerations in Revisions

• 1. Old healed incisions should be used to gain
  access to the hip provided that the surgical
  exposure is not compromised.
• 2. Antibiotics should be withheld until the
  hip-joint capsule has been incised and specimens
  have been obtained.

36

• 3. The choice of surgical approach should be
  based on the need to remove all foreign material
  and dead tissue, including bone, while at the
  same time avoiding devascularization of the
  tissue.
• 4. When all necrotic tissue and foreign material
  have been removed, the wound should be copiously
  irrigated with saline solution.

37
Treatment Protocols

• Antibiotics Without Surgery
• Debridement with Retention of the Prosthesis
• Girdlestone Arthroplasty
• Single-Stage Exchange Arthroplasty
• Two-Stage Exchange Arthroplasty

38
Antibiotics without Surgery

• Most commonly used in the form of suppressive
  therapy when the patient is unfit to undergo
  major surgery or simply refuses further surgical
  treatment.
• The infecting organism must be known as well as
  the sensitivity and MIC.
• The antibiotic must be well tolerated by the
  patient or noncompliance will result.

39
Debridement with Retention of the Prosthesis

• There is little argument about the necessity to
  remove a loose prosthesis from a chronically
  infected joint, however, removal of a well-fixed
  total hip implant carries the risk of causing
  major damage to the remaining bone stock.
• Tsukayama and associates emphasized the
  importance of limiting this tx to infections that
  developed less than 1 month postop.

40

• This did not allow the organisms to produce the
  resistant slime layer and could therefore be
  controlled.
• The primary difficulty appears to be the lack of
  accuracy with which acute infections can be
  distinguished from chronic ones.
• This procedure can only be implemented if the
  history of the infection can be accurately
  identified.

41
Girdlestone Arthroplasty

• The general consensus is that the procedure is
  highly effective in controlling infection and
  reducing pain however, it usually is associated
  with a considerable loss of function. Patients
  walk poorly and almost always need walking aids.
• Limb shortening may range from 3-11cm but most
  typically ranges from 4-6 cm.

42

• This may be appropriate for patients who are
  mentally impaired and who are unable to cooperate
  with the postoperative restrictions.
• Excision arthroplasty is the treatment of choice
  for patients who have an infection and a history
  of intravenous drug abuse.

43
Single-Stage Arthroplasty

• The major advantage of a single-stage exchange
  procedure is the avoidance of additional surgical
  procedures , especially those with medical
  problems that the risks of additional surgeries
  are too high.
• The potential benefits must be weighed against
  the slightly lower rates of eradication of
  infection when compared to the two-stage
  procedures.

44

• Furthermore, the insertion of implant with cement
  is not appropriate in many revision procedures,
  particular when bone stock is deficient.

45
Two-Stage Exchange Arthroplasty

• In North America, periprosthetic infection of the
  hip are most commonly treated with a two-stage
  procedure.
• The principles of the two-stage procedure is to
  remove the implant as well as all of the cement,
  and the necrotic tissue. Then to undergo
  prolonged IV antibiotics, and then to eventually
  reimplant a new prosthesis.

46

• Most protocols have included 6 weeks of
  intravenous antibiotics. There is some evidence
  that the use of IV Abx for less than 4 weeks is
  associated with a higher rate of recurrence when
  the infection is caused by a more virulent
  organism.
• Lieberman and assoc. reported that
  reimplantation after 6 weeks of tx did not differ
  than those patients who were reimplanted after 1
  year.

47
The Authors Protocol

• They use the prosthesis of antibiotic-loaded
  acrylic cement (PROSTALAC), 4-6 weeks of
  antibiotic tx, followed by repeat aspiration of
  the joint at a minimum of 4 weeks after
  discontinuation of the Abx.
• They then proceed with reimplantation if the
  culture is negative and the clinical appearance,
  ESR and CRP level are indicative of resolution of
  infection.

48
Other Surgical Options

• Arthrodesis of the hip should be reserved for
  young, males who have strenuous functional
  demands.
• These usually function well but develop a
  limb-length discrepancy mean of 4.6 cm.

49
Conclusion

• It is necessary to carefully evaluate each
  patient with a periprosthetic infection. First,
  to best determine what stage infection is
  present, then to customize an appropriate
  treatment plan that will first and foremost
  control the infection, then provide the patient
  with best possible functional outcome without
  jeopardizing the patients health and well-being.