Discussion

 Osteomyelitis is defined as an inflammation of the bone caused by an infecting organism  The infection may be limited to a single portion of the bone or may involve numerous regions, such as the marrow, cortex, periosteum, and the surrounding soft tissue.  The infection generally is due to a single organism, but polymicrobial infections can occur, especially in the diabetic foot.

 Traditional System (accdg. to time of onset)  Acute: 2 weeks  Subacute: weeks to months  Chronic: 3 months

 Waldvogel System (accdg. to etiology and chronicity)  Hematogenous  Arising from contiguous infection (no vascular disease present)  Vascular disease present  Chronic

 Cierney and Mader System (accdg. to anatomic extent of infection and physiologic status of host)  1: Medullary only (acute hematogenous)  2: Superficial cortex (contigous spread or soft tissue trauma)  3: Localized (cortical and medullary, mechanically stable)  4: Diffuse (cortical and medullary, mechanically unstable)

 Cierney and Mader System (accdg. to anatomic extent of infection and physiologic status of host)  A: Healthy host  B: Compromised host ▪ Bs: due to systemic factors ▪ Bl: due to local factors ▪ Bls: due to local and systemic factors  C: Treatment worse than disease

 Difficult to eradicate completely  Though systemic symptoms may subside, foci in the bone may contain infected material, infected granulation tissue or a sequestrum  Intermittent acute exacerbations may occur and responds to rest and antibiotics  Hallmark: infected dead bone within a compromised soft-tissue envelope

 The infected foci within the bone are surrounded by sclerotic, relatively avascular bone covered by a thickened periosteum and scarred muscle and subcutaneous tissue  This avascular envelope of scar tissue leaves systemic antibiotics essentially ineffective

 Secondary infections are common  Sinus tract cultures usually do not correlate with cultures obtained at bone biopsy  Multiple organisms may grow from cultures taken from sinus tracks and from open biopsy specimens of surrounding soft tissue and bone

 Generally requires aggressive surgical excision combined with effective antibiotic treatment  Surgery is not always the best option, however, especially in compromised patients

 The diagnosis of chronic osteomyelitis is based on clinical, laboratory, and imaging studies  Gold standard: biopsy specimen for histological and microbiological evaluation of the infected bone  Staphylococcal in most causes, especially posttraumatic  Anaerobes and gram-negative bacilli may also be seen

 Physical examination:  Integrity of skin and soft tissue  Determine areas of tenderness  Assess bone stability  Evaluate neurovascular status of limb

 Laboratory studies:  Generally nonspecific and give no indication of severity ▪ Elevated ESR and CRP ▪ Elevated WBC in 35%

 Radiologic studies:  Plain radiographs ▪ Soft tissue edema and loss of fascial planes (earliest signs of bone infection) ▪ Cortical destruction (7 to 10 days) ▪ Periosteal reaction (2 to 6 weeks) ▪ Sequestrum: dead bone (6 to 8 weeks) ▪ Involucrum: sheath of periosteal new bone (6 to 8 weeks)

 Cortical penetration and accumulation of inflammatory exudates  periosteal stripping  inner layer stimulated to form bone  later infected  “barrier” is formed  cortex and spongiosa deprived of blood supply  necrosis  sinus tract formation in some case  Small sequestra may be resorbed or may be extruded through sinus tract

 Radiologic studies:  Technetium-99m Scanning ▪ Increased uptake in areas of increased blood flow and osteoblastic activity  Gallium Scanning ▪ Increased uptake in areas of leukocyte and bacteria accumulation (can therefor be used to monitor response to surgery)

 Radiologic studies:  CT Scan ▪ Provides excellent definition of cortical bone and a fair evaluation of the surrounding soft tissues and is especially useful in identifying sequestra  MRI ▪ Provides a fairly accurate determination of the extent of the pathological insult by showing the margins of bone and soft-tissue edema ▪ May reveal a well-defined rim of high signal intensity surrounding the focus of active disease (rim sign)

 Generally cannot be eradicated without surgical treatment  Debridement  Curettage  Sequestrectomy  Goal: eradicate infection by achieving a viable and vascular environment  Reconstruction after adequate surgery and appropriate antibiotic therapy

 Limb is splinted until wound is healed  Will also prevent pathologic fractures  Antibiotic regimen is continued from prolonged period and should be monitored by IDS

 Polymethylmethacrylate Antibiotic Bead Chains  Delivers levels of antibiotics locally in concentrations that exceed the minimal inhibitory concentrations  Antibiotic is leached from the PMMA beads into the postoperative wound hematoma and secretion, which act as a transport medium  Aminoglycosides are the most commonly employed antibiotics for use with PMMA beads  Can be used in the treatment of osteomyelitis if soft- tissue coverage is impossible after initial débridement

 Biodegradable Antibiotic Delivery Systems  A second procedure is not required to remove the implant  Soft Tissue Transfer  Fills dead space left behind after extensive débridement  Ilizarov Technique  Allows radical resection of the infected bone  Hyperbaric Oxygen Therapy