Orthopedic Infections, Complications, and Perioperative Care
What this domain tests
Osteomyelitis classification, septic arthritis, prevention bundles, venous thromboembolism, fat embolism, transfusion, and perioperative medical optimization.
Core rules
- Cierny-Mader classifies osteomyelitis by anatomy (I medullary, II superficial, III localized, IV diffuse) and host (A normal, B compromised, C unsuitable for surgery). Host status drives prognosis as much as the bone lesion.
- Native joint septic arthritis is an emergency: arthrocentesis for cell count, Gram stain, and culture, then empirical intravenous antibiotics and prompt washout, usually within 24 hours. Do not delay drainage waiting for culture results.
- Surgical site infection prevention: preoperative chlorhexidine skin preparation, appropriate weight-based antibiotic prophylaxis within one hour of incision, normothermia, glucose control, and avoidance of unnecessary shaving.
- Venous thromboembolism prophylaxis after major arthroplasty follows risk stratification; aspirin, low-molecular-weight heparin, and factor Xa inhibitors are all accepted options, with duration typically 14-35 days.
- Fat embolism syndrome: hypoxemia, neurologic change, and petechiae after long-bone fractures; treatment is supportive, with early stabilization reducing incidence.
Worked example
A 68-year-old with persistent wound drainage ten days after knee arthroplasty has a CRP of 90 mg/L, synovial white cells of 12,000/µL, and Staphylococcus aureus on culture. Because the presentation is within four weeks of implantation, the implant is stable, and the organism is susceptible, debridement with exchange of modular components plus targeted intravenous antibiotics is appropriate; a chronic presentation would require staged exchange.
Traps that cost marks
- Assuming negative cultures rule out infection after antibiotics have been given.
- Choosing debridement and implant retention for a late chronic infection.
- Ignoring host status (Cierny-Mader) when planning treatment.