Periprosthetic infection involving the joint prosthesis and adjacent tissue
Aetiology
Risk factors
Presence of comorbidities e.g. rheumatoid arthiritis, diabetes, malignancy
Use of corticosteriods, TNF inhibitors
Prior arthroplasty or prior infection at surgical site
Prolonged duration of sugery
Postoperative complications
Staph. aureus bacteraemia (from another cause)
Causative organisms
Most commonly staph. aureus and staph. epiderdimis
Cutibacterium acnes - upper limb prostheses
Rarely strep. sp and enterococcus sp.
Gram negatives e.g. E. coli, psudomonas aeruginosa
Very rarely - fungi, mycobacteria sp.
Pathophysiology
Mechanism
Direct inoculation at time of surgery
Manipulation of joint at time of surgery
Seeding of joint at a later time (from bacteraemia)
Classification
Early (within 2-3 weeks) - aquired during sugery or right after
Staph. aureus, coagulase-negative staph (particularly S. epidermis)
Chronic (3 weeks +) - most common, symptoms can be subtle
CoNS (particularly S. epidermis), cutibacterium, corynebacterium, S. aureus
Haematogenous (chronic-late) - abrupt onset, patient can be systemically unwell
S. aureus, GNB
Planktonic vs sessile bacteria
Planktonic bacteria: resposible for most symptoms, bacteraemia
Sessile bacteria: phenotypic transformation of planktonic bacteria to form a biofilm encased in an extracellular matrix (Quorum sensing)
In chronic deep infections the infecting bacteria adhere to the foreign surfaces and form a biofilm which prevents the patient’s immune system attacking
Removal of the infected implants and all foreign material is usually required - DAIR is not enough (need to remove prosthesis)
Clinical presentation
Fever
Joint pain of affected joint
Minimal swelling
Investigations
Culture - perioperative tissue (multiple samples)
If same organism grows from multiple samples this increases significance
Frail patients with chronic infection - Stage 1 exchange
Removal of joint and antibiotics
For frail patients with chronic infection
Chronic infection - Stage 2 exchange
Removal of joint and 6 weeks of aggressive antibiotic therapy
Patient left without a joint for the 6 weeks
Once the infection is under control (wound healed, clean and dry, CRP reduced) a revision joint replacement is performed with more complex joint replacement components
Rifampicin
Rifampicin PO should be added to antibiotics if culture is positive for rifampicin-sensitive staphlococci
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