Summary Osteomyelitis is the infection of bone characterized by progressive inflammatory destruction and apposition of new bone. Diagnosis requires careful assessment of radiographs, MRI and determining the organism via biopsy and cultures. Treatment is often a combination of culture-directed antibiotics and surgical debridement of nonviable tissue. Epidemiology Incidence the exact incidence is unknown Location spine and ribs in dialysis patients medial or lateral clavicle in IV drug abusers foot and decubitus ulcers in diabetics Risk factors recent trauma or surgery immunocompromised patients illicit IV drug use poor vascular supply systemic conditions such as diabetes and sickle cell peripheral neuropathy Etiology Pathophysiology mechanism of spread hematogenous originated or transported by blood may be due to bacterial or viral systemic illness most common etiology in children vertebrae are the most common hematogenous site in adults S. aureus is the most common organism contiguous-spread associated with previous surgery, trauma, wounds, or poor vascularity can be bacterial (most common), mycobacterial, or fungal in nature direct-inoculation penetrating injuries open fractures surgical contamination pathobiology planktonic stage bacteria attach to an inert substrate and undergo apoptosis to create a matrix for biofilm biofilm formation biofilm is characterized by bacteria entering a no-growth, or sessile, phase, which makes them even more resistant to antibiotics that depend on replication to carry out their effect biofilm is then made of an extracellular polymeric substance or exopolysaccharide antibiotics are less effective due to difficulty penetrating the biofilm and bacteria lowering their metabolic rate Associated conditions orthopaedic manifestations septic arthritis abscess medical conditions immunosuppression dialysis IV drug use diabetes poor nutrition vascular disease Organism (see table below) organism varies by age of the patient S. aureus is most common in adults Osteomyelitis Organism Table Newborns (younger than 4 mo) S. aureus, Enterobacter species, group A and B Streptococcus species Children (aged 4 mo to 4 y) S. aureus, group A Streptococcus species, Kingella kingae, and Enterobacter species Children, adolescents (aged 4 y to adult) S. aureus (80%), group A Streptococcus species, H. influenzae, and Enterobacter species Adult S. aureus and occasionally Enterobacter or Streptococcus species Unusual Osteomyelitis Organism Table Salmonella Sickle cell anemia patients (S. aureus is still most common) Pseudomonas IV drug use with AC or SC joint infection or puncture wound through rubber soled shoes Bartonella HIV/AIDS patient following cat scratch or bite Fungal osteomyelitis Immunosuppressed, long-term IV medications, or parenteral nutrition Tuberculosis Manifestations include Potts disease Classification Timing classification acute within 2 weeks subacute within one to several months chronic after several months Cierny-Mader classification Cierny-Mader Classification of Osteomyelitis (describes anatomic involvement, host, treatment, prognosis) Anatomic Location Stage 1 Medullary Stage 2 Superficial Stage 3 Localized Stage 4 Diffuse Host type Type A Normal Type BL Locally compromised Type BS Systemically compromised Type C Treatment is worse to the patient than infection Presentation History duration prior treatments characterize host immunocompromised Symptoms pain fever more common in acute osteomyelitis Physical exam vital signs fever, tachycardia, and hypotension suggest sepsis inspection erythema, tenderness, and edema are commonly seen draining sinus tract more common in chronic osteomyelitis if able to probe bone through sinus, chronic osteomyelitis is present motion limp and/or pain inhibition with weight-bearing or motion may be present assess the joints above and below the area of concern neurovascular assessment of vascular insufficiency locally or systemically Imaging Radiographs recommended views orthogonal plain radiographs of the affected extremity findings acute imaging findings lag behind by 2 weeks bone loss must be 50% before evident on plain films chronic bone lucency, sclerotic rim, osteopenia, periosteal reaction, and lysis around hardware sequestrum: devitalized bone that serves as a nidus for infection involucrum: formation of new bone around an area of bony necrosis Brodie's abscess sensitivity and specificity is variable CT indications assist in diagnosis and surgical planning by identifying necrotic bone sensitivity and specificity may be affected by hardware artifact and scatter MRI indications assists in the diagnosis and surgical planning best test for diagnosing early osteomyelitis and localizing infection views T2 sequences will show bone and soft tissue edema findings penumbra sign T1 - dark central abscess with bright internal wall and dark external sclerotic rim sensitivity and specificity if negative rules out osteomyelitis if positive may overestimate the extent of osteomyelitis Nuclear medicine technetium bone scan indications when radiographs are normal and MRI is not an option sensitivity and specificity highly sensitive but not specific if negative rules out osteomyelitis gallium scan indications diabetic foot or if MRI is not an option sensitivity and specificity cellulitis may cause false positive if negative rules out osteomyelitis Studies Laboratory analysis leukocyte count (WBC) only elevated in 1/3 of acute osteomyelitis erythrocyte sedimentation rate (ESR) usually elevated in both acute and chronic osteomyelitis (90%) a decrease in ESR after treatment is a favorable prognostic indicator C-reactive protein most sensitive test with elevation in 97% of cases decreases faster than ESR in successfully treated patients blood cultures often negative, but may be used to guide therapy for hematogenous osteomyelitis Microbiology sinus tract cultures not reliable for guiding antibiotic therapy culture of bone gold-standard for guiding antibiotic therapy Histology acute osteomyelitis live osteocytes with numerous acute inflammatory cells (neutrophils) chronic osteomyelitis no nuclei in osteocytes with fibrosis of marrow and chronic inflammatory cells (lymphocytes) Differential Key differential benign tumor biopsy all infection, cultures all tumors malignant tumor biopsy all infection, cultures all tumors healing fracture Treatment Goals success in the treatment is dependent on various factors patient factors immunocompetence of patient nutritional status injury factors the severity of the injury as demonstrated by segmental bone loss infection location metaphyseal infections heal better than mid-diaphyseal infections other factors affecting prognosis and treatment include: residual foreign materials and/or ischemic and necrotic tissues inappropriate antibiotic coverage lack of patient cooperation or desire Nonoperative Treatment suppressive antibiotics indications when operative intervention is not feasible hyperbaric oxygen therapy indications can be used as adjunct in refractory osteomyelitis Operative treatment irrigation and debridement followed by organism specific antibiotics indications acute osteomyelitis that fails to improve on IV antibiotics subacute osteomyelitis abscess formation chronic osteomyelitis draining sinus amputation indications chronic infection with pervasive wound or bone damage that is unable to be salvaged Techniques Antibiotic therapy technique antibiotics should be tailored to a specific organism, preferably after a bone biopsy is obtained chronic suppressive antibiotics may be useful in patients who are immunocompromised or in whom surgery is not feasible high rates of recurrence if suppressive antibiotics are discontinued Irrigation & debridement soft tissue all devitalized and necrotic tissue should be removed extensive debridement is essential to eradicate the infection bone work sequestrum must be eliminated from the body, or infection is likely to recur debride bone until punctate bleeding is seen - "paprika sign" hardware removal any non-essential hardware should be removed dead space management goal is to replace dead bone and scar tissue with vascularized tissue options include vascularized bone grafts local tissue flaps or free flaps antibiotic-impregnated acrylic beads (PMMA) vacuum-assisted closure improves wound healing and dead space closure in multiple ways remove interstitial fluids eliminate superficial purulence or slime allow arterioles to dilate, which allows granulation tissue to proliferate decrease in capillary afterload to promote inflow of blood mechanical force on wound edges draws them in instrumentation bony stability is required for successful eradication of infection external fixation preferred to internal fixation surgical fixation techniques antibiotic-impregnated acrylic (PMMA) Intramedullary nail peak antibiotic elution is 24 hours after placement duration of antibiotics elution is generally up to 4 months Ilizarov technique intramedullary nail with or without external fixation Masquelet technique in situ reconstruction mechanism is thought to be related to improved angiogenesis outcomes often requires staged approach with multiple debridements and delayed soft tissue coverage when combined with postoperative antibiotics tailored to a specific organism, treatment is often successful Amputation technique amputation at the level that will eradicate infected tissue to healing tissue with capacity to heal Complications Persistence or extension of infection Amputation Sepsis Malignant transformation incidence 1% in chronic osteomyelitis most commonly squamous cell carcinoma (Marjolin's ulcer) risk factors chronic draining sinus treatment wide surgical resection Prognosis Despite surgical debridement and long-term antibiotics, recurrence rate of chronic osteomyelitis in adults is 30% Poor prognosis in patients with major nutritional or systemic disorders