OSTEOMYELITIS. If it occurs in adults, then the axial skeleton is the usual site.

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1 OSTEOMYELITIS Introduction Osteomyelitis is an acute or chronic inflammatory process of the bone and its structures secondary to infection with pyogenic organisms. Pathophysiology Osteomyelitis may be acute or chronic. Acute: There are two recognized types: 1. Acute hematogenous osteomyelitis: Is characterized by an acute infection of the bone caused by the seeding of the bacteria within the bone from a remote source. This condition is most commonly seen in children. The most common site in children is the rapidly growing and highly vascular metaphysis of long bones, especially the tibia and femur. If it occurs in adults, then the axial skeleton is the usual site. Acute hematogenous osteomyelitis, despite its name, may have a slow clinical development and insidious onset. 2. Direct inoculation (or contiguous-focus) osteomyelitis: Is an infection in the bone secondary to the inoculation of organisms from direct penetrating trauma, or following a surgical procedure. Clinical manifestations of direct inoculation osteomyelitis tend to be more localized than those of hematogenous osteomyelitis and more often involve multiple organisms. Chronic osteomyelitis: Chronic osteomyelitis persists or recurs, regardless of its initial cause and/or mechanism and despite aggressive intervention.

2 Organisms: 1. Staphylococcus aureus is the most frequent causative organism in all types of osteomyelitis. 2. Streptococcus. 3. Hemophilus influenzae In diabetics, immunocompromised, nosocomial and chronic infections: 4. Gram negative, enterobacteria 5. Pseudomonas aeruginosa 6. Mycobacterium tuberculosis Predisposing Factors: 1. Penetrating trauma. 2. Compound fractures 3. Surgical procedures 4. Foreign bodies within bone, including surgical prostheses 5. Dead bone, (ischemic necrosis of bone results in the separation of devascularised fragments known as sequestra) 6. Peripheral vascular disease, especially in association with diabetes. Involvement here is usually seen in the feet. 7. Immunosuppression Complications: 1. Bone abscess. 2. Bacteremia. 3. Pathological fracture 4. Loosening of the prosthetic implant 5. Overlying soft-tissue cellulitis, including gas forming infections. 6. Chronic draining soft-tissue sinus tracts

3 Clinical Features 1. Fever, may or may not be present. 2. Local pain and tenderness. 3. In children, reluctance or non use of a limb may be the presenting feature. 4. Chronic osteomyelitis may be associated with nonhealing ulcers and sinus tract drainage. Investigations Blood tests: FBE CRP U&Es / glucose. Blood cultures. Plain X-rays: X-ray evidence of acute osteomyelitis first is suggested by overlying soft-tissue edema at 3-5 days after infection. Bony changes are not evident for at least days and initially manifest as periosteal elevation followed by cortical or medullary lucencies. Approximately 40-50% focal bone loss is necessary to cause detectable lucency on plain films. Bone scan: A 3-phase bone scan with technetium 99m is the imaging modality of choice, where the plain X-ray results are not helpful. CT scan: Can detect evidence of osteomyelitis before any plain X-ray changes. CT scans can depict abnormal calcification, ossification, and intracortical abnormalities. It probably is most useful in the evaluation of spinal vertebral lesions.

4 MRI; Can detect evidence of osteomyelitis before any plain X-ray changes. The MRI is effective in the early detection of osteomyelitis. It may detect it even before bone nuclear medicine scanning or CT scanning. Sensitivity ranges from %. Microbiology; If there is any sinus discharge, this may be sent for micro and culture, although results from this may be misleading in chronic infections. On occasions only the histopathological examination of a bone biopsy specimen will permit the accurate diagnosis of osteomyelitis. This is especially the case for vertebral infections. If all cultures are negative, tuberculosis or malignancy needs to be considered. Making the diagnosis Diagnosis requires 2 of the 4 following criteria: Purulent material on aspiration of affected bone. Positive findings of bone tissue or blood culture. Localized classic physical findings of bony tenderness, with overlying soft-tissue erythema or edema. Positive radiological imaging study. Management 1. Attend to any immediate ABC issues, if the patient is unwell. 2. IV access, take bloods. 3. Give analgesia as clinically indicated 4. Antibiotic therapy: 1 Empirical therapy should be with flucloxacillin. Cefotaxime should be added for children less than 5 years not immunized against Haemophilus Influenzae type B, or if gram negative sepsis is suspected.

5 For patients allergic to penicillin, clindamycin or lincomycin should be used. Antibiotic treatment will need to be continued for a minimum of 4-6 weeks. In chronic osteomyelitis, many months may be required. The exact timing of the institution of antibiotics in cases of suspected osteomyelitis, as for cases of suspected, osteomyelitis, is problematic. In general terms antibiotics should not be given until an orthopedic review or opinion has been obtained. This is because it is important to obtain a microbiological specimen for culture and sensitivity testing before any antibiotics are given. In certain cases empiric antibiotics should be given, however. These cases include: The patient appears septic / unwell. The patient has significant underlying immunocompromise, (such as febrile neutropenia or recent chemotherapy) There is a suspicion of meningococcus infection. The diagnosis is unclear, especially if the patient is unwell or has immunological risk factors. There will be a significant delay before an orthopedic consultation can be obtained. The amount of acceptable delay will need to be judged on a case by case basis. If unsure discuss the case with the ED consultant. 5. Osteomyelitis in association with surgical prostheses is extremely difficult to treat. 1 The best chance of cure is in those patients who present within 2 weeks of surgery. Cure rates of less than 50% have been reported for the more chronic infections if the prosthetic material is not removed. If prosthesis removal is not possible, a cure is ultimately unlikely and suppression of infection with long term antibiotics will be necessary. 6. All cases of suspected osteomyelitis must be referred o the orthopedic unit.

6 References: 1. Antibiotic Therapeutic Guidelines, Version 12, Lew DP, Osteomyelitis, NEJM vol 336 (14) April , p Dr J Hayes Mr Miron Goldwasser, Head Orthopedics Unit Northern Hospital. Reviewed 6 February 2006