- Over 100,000 knee and hip replacements are performed in the UK each year
- Most are carried out with few complications
- Infections is an uncommon but devastating complication
- Occurs in approximately 1% cases
- Results in major morbidity and considerable cost
- Risk can be reduced by:
- Excluding patients who have active infection
- Antibiotic prophylaxis
- Careful theatre technique
Microbiology
- Commonest organisms identified are:
- Coagulase-negative staphylococcus (45%)
- Staph. aureus (35%)
- Streptococci (10%)
- Gram-negative bacteria (<5%)
- Early infection results form intraoperative contamination
- Late infection usually results from haematogenous spread
- Bacteria adhere to prosthetic material and produce a biofilm
- Biofilm isolates the bacteria from host defences and antibiotics
- Significant infection can result from small bacterial inoculum
- A low-grade inflammatory process then occurs
- This leads to bone erosion and loss of bone stock
Clinical features
- Acute infection presents with sign of a wound infection
- A purulent discharge from the wound is often present
- Chronic infection presents more insidiously
- Pain is often the prominent symptom
- The diagnosis of chronic infection can be difficult
Investigation
- The following investigations should be considered
- Microbial culture
- Inflammatory markers
- Plain radiography
- Bone scan
- Histology
- Molecular methods
- Diagnosis depend on identification of bacteria from fluid around joint
Management
- Antibiotics should be started once diagnosis is considered
- Rarely eradicate establish infection
- Antibiotic choice should be based on culture results
- If cultures are negative or unavailable then vancomycin is the organism of choice
Surgery
- In acute infection joint debridement and washout may be appropriate
- In chronic infection with a loose joint, implant should be removed
- Revision surgery can be performed as a one-stage or two-stage procedure
- If insertion of new prosthesis is impossible consider:
- Excision arthroplasty
- Joint fusion
- Complications following revision joint surgery include:
- Massive bone loss
- Periprosthetic fracture
- Recurrence of infection
Bibliography
Gillespie W J. prevention and management of infection after total joint replacement. Clin
Infect Dis 1997; 25: 1310-1317.
Nelson C L. Primary and delayed exchange for infected total knee arthroplasty. Am J Knee Surg
2001: 14; 60-64.
Kaltas D S. Infection after total hips arthroplasty. Ann R Coll Surg Engl 2004;
86: 267-271. |