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The management of prosthetic joint infection (PJI) following total hip (THA) remains challenging.
PJIs are associated with significant morbidity and socioeconomic burden

The incidence of PJI is set to rise.This relates in part to 
  • Changes in patient related factors(more comorbidities)
  • Changes in microbiology(increased virulence,more resistant strains emerging)
  • Improved diagnostic methods
  • Use of different and new definitions

Until recently there was no single accepted set of diagnostic criteria for PHI. Various definitions had been proposed; however, none were widely adopted. Furthermore, some of these definitions disagree with each other. Therefore, a workgroup convened by the Musculoskeletal Infection Society (MSIS) analysed the available evidence to propose a new definition for PJI.

Major criteria -diagnosis can be made when 1 major criteria exists
1.Sinus tract communicating prosthesis
2.Pathogen isolated by culture from 2 separate tissue/fluid samples obtained from the  affected prosthetic joint

Minor criteria -diagnosis can be made when 4 out of 6 criteria exist:
1.Elevated ESR(>30mm/h) and CRP(>10mg/L)
2.Elevated synovial leukocyte count
3.Elevated synovial neutrophil percentage (PMN%)
4.Presence purulence affected joint
5.Isolation of a microorganism in one culture of periprosthetic tissue or fluid
6.Greater than 5 neutrophils per high-power field in 5 high-power fields observed from histologic analysis of periprosthetic tissue at ×400 magnification.

Rationale DAIR procedure

  • Retain the implant and avoid further more invasive/complex surgery
  • Reduces the infective organism  load
  • Less complicated than revision arthroplasty
  • Reduced morbidity,length of stay and costs
  • Attractive elderly or infirm  patient
  • Aiming for a complete debridement of all infected,dead and non viable tissue around a solidly fixed prosthesis which is cleaned as best as possible to remove and prevent production biofilm by infecting organisms

In the case of a modular total knee arthroplasty, removal of the polyethylene tibial insert is very important in order to gain access to posterior aspect of the joint. Choi et al. showed that not exchanging the polyethylene insert was an independent risk factor for failure. Based on this, patients with an all polyethylene tibial component might not be good candidates for implant retention

When to use DAIR

  • Especially for acute post operative period within 4 weeks of surgery(ideally 1 week)
  • Acute haematogenous infection within 2 weeks of onset
Greater infection eradication with DAIR when used in early PJI.
Best results seen with an interval less than a week between onset of symptoms and exchange of modular components with the DAIR procedure 


Outcomes following a single-stage procedure are affected by many factors based on the immunological status of the patient, the local soft-tissue and bony characteristics, and the microbiological profile.
Promising infection-free outcomes have been reported when strict criteria for the selection of patients are applied
Early experience of single-staged exchange arthroplasty by Buchholz et al in 1981, reported an overall success rate of 77% in a series of 583 patients.They noted that the microbiological profile was important in determining outcome, with polymicrobial infections and atypical and gram-negative organisms being associated with a higher failure rate.
Jackson et al, in 2000, in a review of the literature concluded that in addition to these factors, infection with MRSA or MRSE resistant organisms was associated with a poor outcome.

Advantages
As it involves fewer surgical procedures
It is  more cost-effective, with a shorter period of hospitalization and reduced use of antibiotics.

Disadvantages 
Aggressive debridement of bone and soft tissue with removal of components and cement may be required, that  can result in significant bone loss requiring expert reconstructive surgery.

Considered the "Gold standard" to eradicate periprosthetic joint infection.

Single-stage revision has become more popular in recent years, following the publication of a number of studies reporting comparable,if not better, outcomes of single stage compared with two-stage procedures with an associated reduction in morbidity, mortality, and financial and sociological burden

CASE BASED DISCUSSIONS

Case Based Dicussion :PJI

Have an agreed definition for PJI worked out beforehand for the exam.

Question:What is DAIR
DAIR involves 
  • Withholding antibiotics and aspiration of the joint
  • Removal of skin margins and excision of any sinus tracks
  • Subcutaneous space and fascia is opened,tissues are debridement and sent for microbiology
  • Intra-articular space is opened with radical debridement all infected and necrotic tissue. Synovectomy performed.More tissue samples are sent for microbiology
  • Exchange of ALL removable implants
  • Thorough lavage(use of 0.05% gluconate/ betadine) of the joint.
  • Suction drain is left in situ until minimal drainage then removed

Question :What are the advantages of DAIR

  • Less complicated than revision arthroplasty
  • Avoids the removal solidly fixed implant loss bone stock & risks perioperative fracture
  • Reduced morbidity,length of stay and costs

Question :What are the pitfalls with DAIR

  • Not arthroscopic as this does not allow adequate debridement or exchange of the PE insert
  • Repeated DAIR is not recommended
  • If the implant is radiologically loose  needs to be managed with a staged revision

Question:Which patients are not candidates for DAIR

  • Persistence of a sinus
  • Immunocompromised patient
  • Acute infections better chance of success (31-100%) than late chronic infection (28-62%)

Question:What do you mean by late chronic 

By late chronic the implant has been in years and the infection has been present for several weeks

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QUESTION 1 OF 1

A 69-year-old woman is seen as an emergency add on to the orthopaedic clinic. She underwent cemented total hip arthroplasty 10 days previously. Her wound has been persistently draining since she was discharged from hospital. She is well within herself, apyrexia with minimal hip pain.
The next most appropriate course of action is to

QUESTION ID: 1170

1. A. Aspirate the hip
2. B. DAIR hip
3. C. Discontinue anticoagulation treatment
4. D. Start oral antibiotics
5. E. Swab the wound

References

  • 1. Parvizi J, Zmistowski B, Berbari EF, Bauer TW, Springer BD, Della Valle CJ, Garvin KL, Mont MA, Wongworawat MD, Zalavras CG. New definition for periprosthetic joint infection: from the Workgroup of the Musculoskeletal Infection Society. Clin Orthop Relat Res. 2011 Nov;469(11):2992-4.