Osteomyelitis can arise from bacteria circulating in the bloodstream due to joint replacement, an infection near the bone, or a traumatic inoculation. In this video, you'll find out which organisms are usually responsible for these infections in various populations, the clinical findings that suggest chronic (versus acute) osteomyelitis, and how to manage both conditions.
[00:00:00] Osteomyelitis or bone infection can arise from bacteria circulating in the bloodstream hematogenously from organisms in infections present near bones, contiguous infections, from traumatic inoculation or as a result of complication of joint replacement. 80% of bone infections are caused by Staphylococcus aureus but there are other organisms
[00:00:30] linked to the age of the patient and predisposing conditions. In children under the age of two years. Kingella kingae, a Gram-negative aerobic coccus is one of the most common causes of bone and joint infections. Older Persons who have more frequent hospitalizations and more intravenous infusions, bladder and intro vascular catheters are more susceptible to staphylococcal bacteremia and Gram-negative rod bacteria which
[00:01:00] can infect bones. Patients with sickle cell anemia develop multiple infarcts in bones which are susceptible to colonization by bacteria in the bloodstream. Salmonella bacteria is more common in these patients compared to others. Dog and especially cat bites may be directly associated with osteomyelitis caused by Pasteurella Multocida. Acute osteomyelitis is most common in infants
[00:01:30] and children and is hematogenous in origin. Staphylococcus aureus is the most common organism involved but streptococci or Haemophilus influenzae can cause the disease as well. In infants, the nearby joint is often involved because the joint capsule surrounds the epiphysis and diaphysis. Concomitant joint infections are not common in older children and adults because the joint capsule is outside the epiphysis.
[00:02:00] Acute osteomyelitis generally presents with fever, with or without chills, focal pain, redness, and tenderness over the involved bone. The white blood cell count is moderately high with a predominance of neutrophils and bands, a rapid erythrocyte sedimentation rate, and elevated C-reactive protein. X-ray imaging shows radiolucencies and occasionally an elevated periosteum.
[00:02:30] Magnetic resonance imaging or MRI show areas of enhancement in bone marrow. Vertebral osteomyelitis like acute osteomyelitis in children is usually hematogenous in origin and may result from an infected intravenous access, urosepsis or from dental abscesses. Thus, the microbiology often involves Staphylococcus aureus, enteric bacteria or mixed mouth flora.
[00:03:00] Fewer than half of the patients are febrile but focal pain and tenderness of the spine is characteristic. Bone infections are difficult to eradicate and any microbial therapy is necessarily prolonged, therefore, it is crucial to biopsy involved bone to make an exact microbiologic diagnosis to tailor antimicrobial therapy to the best regimen. Biopsies must be performed
[00:03:30] prior to any microbial treatment and can be done via a needle or open biopsy. For acute osteomyelitis in infants, empirical therapy with vancomycin to cover Gram-positive organisms including MRSA plus cefepime to cover Gram-negatives is preferred. For older children, the bone biopsy should be sent for cultures and Gram stain. If Gram-positive organisms
[00:04:00] are present, vancomycin should be begun empirically. If cultures yield methicillin-susceptible Staphylococcus aureus, intravenous nafcillin or oxacillin should be substituted for vancomycin. In children, three weeks of antibiotic treatment is usually sufficient. Debridement of bone is rarely necessary unless there is antibiotic failure. Moreover, once the infection
[00:04:30] is clearly improved, therapy may be switched to oral antibiotics. Chronic osteomyelitis often follows a traumatic wound with fractures requiring open reduction and internal fixation. Symptoms may be subtle since patients are left with residual chronic symptoms from the original injury. Signs of infection may come and go with overlying redness, pain, increased warmth
[00:05:00] and tenderness over the underlying bone. Purulent drainage through fistula's tracts may emerge from the area. Overall, Staphylococcus aureus is the most common cause in upper or lower extremities but Gram-negative organisms may be found especially in lower extremity infections. Imaging of bone often shows lucencies and periosteal elevation and a frank abscess and bone may occur called Brodie's
[00:05:30] abscess. Treatment of chronic osteomyelitis first involves surgical debridement of all dead bone and if the remaining defect is large, covering of the wound with skin and or muscle flaps. Four to six weeks of antibiotic therapy is usually required and it's based upon the results of cultures from the debrided tissue. Drugs with long half-lives such as ceftriaxone and ertapenem
[00:06:00] are often chosen because they can often be given once daily as outpatients. However, broad-spectrum agents use for a long time when not absolutely necessary increase the risk of multidrug-resistant bacteria. So it's best to de-escalate treatment based on the culture results when possible. Many surgeons place antibiotic-impregnated polymethylmethacrylate beads into the wound as part of local therapy especially if the wound contains
[00:06:30] large areas of dead space after surgery. Procedures are mainly a surgical decision and antibiotics have to be adapted to cultures and to remaining defects in the infected bone.