Infectiology & Orthopedics & Internal Medicine
Osteomyelitis | Omicron Clinic, Quebec
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Osteomyelitis is an infection of the bone - bone cortex, bone marrow and periosteum - usually of bacterial origin, more rarely of fungal or mycobacterial origin, characterized by destructive inflammation of bone tissue that can progress to necrosis (formation of avascular bone sequestration), skin fistulization and chronicity if treatment is inadequate or delayed. It is classified according to its mode of contamination - hematogenous (bacterial dissemination via the bloodstream, predominant in children) or by contiguity (extension from an adjacent infectious site - traumatic wound, diabetic foot ulcer, bone surgery) - and according to its evolution - acute (less than 2 weeks), sub-acute (2 weeks to 3 months) or chronic (beyond 3 months). Staphylococcus aureus is the pathogenic agent responsible for 40 to 70 % of all osteomyelitis cases, regardless of age or mode of contamination, due to its multiple virulence factors favoring adhesion to the bone matrix (protein A, teichoic acid, fibronectin-binding proteins) and biofilm formation on bone sequestrates and prosthetic material - staphylococcal biofilm being particularly difficult to eradicate by antibiotics and host immune mechanisms. In newborns and infants, group B streptococci and enterobacteria (Escherichia coli, Klebsiella) are frequent agents. In sickle-cell patients, Salmonella spp. is a specific and important cause of osteomyelitis. MRSA (methicillin-resistant Staphylococcus aureus) infections are a growing concern, particularly in nosocomial osteomyelitis and infections on prosthetic material. Diagnosis is based on a combination of suggestive clinical signs, biological inflammatory syndrome and, above all, imaging - MRI being the reference method - and microbiology by guided bone biopsy, which is essential to obtain a precise bacteriological diagnosis enabling targeted antibiotic therapy. Treatment involves prolonged antibiotic therapy (4 to 6 weeks, sometimes up to 3 to 6 months in chronic forms) and surgical debridement of necrotic tissue in complicated forms.
Classification, contamination routes and pathogens
| Clinical form | Population and context | Main pathogens |
|---|---|---|
| Acute hematogenous osteomyelitis in children | Children 2 to 12 years old + preferentially affects the metaphyses of long bones with strong vascularization (distal femur + proximal tibia + proximal humerus) + transient bacteremia (often after minor trauma) → septic emboli in metaphyseal capillaries (sinusoidal vascular loops with low flow → bacterial retention) | S. aureus (50-70 %) + Streptococcus pyogenes (Group A) + (Group B) Streptococcus agalactiae (group B - infant) + Haemophilus influenzae (unvaccinated child < 5 years - rare since Hib) + Kingella kingae (child < 5 years - increasing) |
| Hematogenous osteomyelitis in adults | Adult + primary infectious focus identifiable in 50 % of cases (endocarditis + urinary tract infection + catheter + IV access in IVDU) + vertebrae +++ (spondylodiscitis - see differential diagnosis) + long bones less frequent than in children | S. aureus (40-60 %) + Streptococcus spp. + enterobacteria (E. coli + Klebsiella) in elderly or urological patients +. Pseudomonas aeruginosa (IVDU + heroin addicts) + Candida spp. (immunocompromised) |
| Contiguous osteomyelitis - diabetic foot ulcer | Most common form in adults in Western countries + peripheral neuropathy + obliterative arteriopathy + chronic plantar ulcers + preferential involvement of foot bones (metatarsals + phalanges + calcaneus) + diagnosis often delayed by absence of pain (neuropathy) | Polymicrobial in 50-75 % of cases: S. aureus (dominant) + streptococci + enterobacteria (Proteus + E. coli) + anaerobic (Bacteroides + Peptostreptococcus) + Pseudomonas aeruginosa (chronic wound + water exposure) |
| Post-traumatic or post-surgical osteomyelitis | Open fractures + orthopedic surgery (osteosynthesis + joint prostheses) + intraoperative contamination or traumatic wound + surgical material (plates + nails + prostheses) favors bacterial biofilm formation | S. aureus (dominant) + coagulase-negative staphylococci (S. epidermidis - biofilm ++ on material) + Gram-negative (Pseudomonas + enterobacteria) |
| Osteomyelitis in the immunocompromised and special forms | Sickle cell disease: Salmonella spp. (specific cause - bone marrow ischemia + bacteremia) + HIV : Mycobacterium avium + fungi + Bartonella + bone tuberculosis (Pott's disease - tuberculous spondylodiscitis) | Depending on the terrain : Salmonella (sickle cell anemia) + Mycobacterium tuberculosis (bone tuberculosis) + (bone tuberculosis) Aspergillus + Candida (immunocompromised) + (immunocompromised) + (immunocompromised) + (immunocompromised) Bartonella henselae (HIV) |
Clinical presentation
- Acute hematogenous osteomyelitis in children: often abrupt onset + high fever (39-40°C) + intense localized bone pain + refusal to support or mobilize the affected limb (lameness + pseudo-paralysis in infants) + exquisite point of pain on palpation of the metaphysis + erythema + local heat + edema within a few hours to days + without treatment → subperiosteal abscess + spontaneous drainage + skin fistula + passage to chronicity
- Adult osteomyelitis - diabetic foot : chronic non-healing plantar ulcer + often painless (neuropathy) + palpable bone at the bottom of the ulcer (positive stylet sign - sensitivity 89 %, specificity 85 %) + erythema + oedema + local warmth + characteristic odour if anaerobic + purulent drainage + absence of pain should not be reassuring - neuropathic diabetics may have advanced osteomyelitis with no pain complaints.
- Chronic osteomyelitis : chronic bone pain, dull + intermittent + exacerbated during relapses + skin fistula with chronic purulent drainage (pathognomonic of chronic osteomyelitis) + bone sequestrum (necrotic, avascular bone fragment visible on imaging) + absence of fever outside acute relapses + inflammatory biology less disturbed than in acute phase
- Biology : hyperleukocytosis with neutrophilic polynucleosis (especially in acute phase) + elevated CRP (often > 50-100 mg/L) + accelerated VS + elevated PCT (procalcitonin) in bacteremic forms + positive blood cultures in 50-60 % of acute hematogenous osteomyelitis in children + less often positive in adult and contiguous forms
Imaging diagnosis
| Imaging | Diagnostic signs and performance | Indications and limitations |
|---|---|---|
| MRI - reference method | Sensitivity 90-100 % + specificity 79-90 % + T2 hypersignal and STIR of bone marrow (infectious medullary edema) + T1 hyposignal replacement of medullary fat + contrast enhancement after gadolinium + visualization of subperiosteal abscess + extent of infection in soft tissue + bone sequestrum (area of non-contrast enhancement) | Examination of choice for early diagnosis (positive from D3-J5 of infection) + preoperative evaluation + monitoring under treatment + limitations: cost + availability + artifacts on metallic material (prostheses + osteosynthesis) |
| Standard radiography | Normal in the first 7 to 14 days of infection (time to visible bone destruction) + late signs: focal osteolysis + periosteal reaction + cortical irregularity + sequestrum (densification in an area of osteolysis) + involucrum (peripheral bone neoformation) | First examination carried out + not very sensitive in the early acute phase but useful for differential diagnosis (fracture + tumour) and long-term follow-up + essential before any other imaging. |
| Technetium-99m bone scan | Sensitivity 80-90 % + specificity 70-80 % + hyperfixation in the 3 phases (vascular + tissue + bone) as early as D2-J3 of infection + exploration of the entire skeleton in a single acquisition (useful if multiple or unknown focus). | Useful if MRI is not available or if multiple foci are being sought + less effective than MRI for delineating local extension + many false positives (fractures + tumors + non-infectious inflammation) + SPECT-CT improves specificity |
| PET scan (18F-FDG) | Sensitivity 96 % + specificity 91 % + carbohydrate hypermetabolism of the infection site + particularly effective for chronic osteomyelitis + infections on prosthetic material and spondylodiscitis | Better performance than scintigraphy for chronic infections and on material + limited availability and high cost in Quebec + reserve for complex or discordant cases |
| Ultrasound | Detection of subperiosteal abscess (periosteal fluid collection) + associated joint effusion + soft tissue collection + guides punctures and biopsies | Useful especially in children to detect incipient subperiosteal abscesses + guides bone biopsy or abscess puncture + no information on bone marrow (unlike MRI). |
ℹ️
Bone biopsy with microbiological culture is essential before prolonged antibiotic treatment of osteomyelitis - except in cases of sepsis requiring urgent empirical treatment. Without precise identification of the pathogen and its antibiogram, treatment is likely to be inadequate, favoring the selection of resistance and the transition to chronicity. In adults with diabetic foot osteomyelitis, bone biopsy by clean surgery (not through the infected wound) is the diagnostic standard recommended by IDSA guidelines.
Antibiotic treatment
- General principle - documented antibiotic therapy : start empirical IV antibiotic therapy as a matter of urgency if sepsis or severe acute osteomyelitis + after microbiological sampling (blood cultures + bone biopsy) + then adapt according to the antibiogram as soon as possible + total duration: 4 to 6 weeks for acute forms (including 1 to 2 weeks IV followed by oral relief for uncomplicated forms) + 6 weeks to 6 months for chronic forms
- Osteomyelitis S. aureus meticillin-sensitive (SAMS) : flucloxacillin 2 g IV every 4 hours (Canada + Europe) + or cefazolin 2 g IV every 8 hours (well-tolerated equivalent + SC route possible) + oral relief: cloxacillin + cefalexin + or amoxicillin-clavulanate depending on sensitivity + duration 4 to 6 weeks
- MRSA (methicillin-resistant Staphylococcus aureus) osteomyelitis: vancomycin IV (target AUC/CMI ≥ 400-600) + or daptomycin 6 mg/kg/d IV + oral relief if well tolerated and bioavailable: linezolid 600 mg × 2/d + or cotrimoxazole + rifampicin (synergistic combination for biofilm) + duration 6 weeks minimum
- Osteomyelitis multiforme (diabetic foot) : piperacillin-tazobactam IV + or ertapenem + or ampicillin-sulbactam + anaerobic coverage mandatory + adaptation according to bone biopsy cultures + rifampicin may be added for its activity on biofilm + duration 6 weeks after the last surgical debridement
- Tuberculous osteomyelitis (Pott's disease) : standard quadruple anti-tuberculosis therapy (isoniazid + rifampicin + pyrazinamide + ethambutol × 2 months + then dual therapy × 4 months) + specialist infectious diseases opinion + surgical stabilization if vertebral instability
- Rifampicin in combination : active on staphylococci in biofilm phase (stationary) + NEVER as monotherapy (rapid selection of resistance) + always in combination + numerous drug interactions (CYP3A4 enzyme inducer) + to be initiated after the active bacteremia phase to avoid selection of resistance
Surgical treatment
- Formal indications : collected subperiosteal or intraosseous abscess + bone sequestrum (avascular necrotic bone tissue inaccessible to antibiotics) + failure of antibiotic therapy alone after 48-72 hours + associated septic arthritis (urgent joint drainage) + vertebral instability (complicated spondylodiscitis) + infected hardware (prosthesis + osteosynthesis hardware)
- Surgical techniques : bone curettage (removal of infected and necrotic tissue) + sequestrectomy + fistulectomy + irrigation-drainage + bone reconstruction (bone graft + musculocutaneous flaps to fill loss of substance) + removal of infected material + two-stage prosthetic replacement (removal + antibiotic therapy + reimplantation after infectious eradication)
- Treatment of the diabetic foot with osteomyelitis : surgical debridement of necrotic tissue + resection of infected bone (resection arthroplasty + radius or transmetatarsal amputation if necessary) + revascularization if severe arteriopathy limits healing + strict unloading of the foot (full-contact cast + wheelchair)
Situations requiring urgent medical assessment
Call 911 or go immediately to emergency if severe localized bone pain is accompanied by high fever + chills + or signs of sepsis (hypotension + tachycardia + confusion) - acute hematogenous osteomyelitis with bacteremia can progress to septic shock within hours, and requires urgent IV antibiotic therapy after blood cultures. In the case of a child presenting with refusal of support or mobilization of a limb associated with fever, osteomyelitis or septic arthritis must be suspected and evaluated in the paediatric emergency department without delay - the functional prognosis of the joint depends on early drainage if septic arthritis is associated.
For diabetic patients presenting with a foot ulcer that has not healed for more than 2 weeks, a rapid medical consultation is recommended to assess the presence of underlying osteomyelitis by clinical examination (stylet test + MRI of the foot) and initiate multidisciplinary management (infectiology + vascular surgery + podiatry). To book an appointment at one of our points of service in Quebec or via telemedicine, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's specialized physicians and nurse practitioners (SPNs) ensure early diagnosis of osteomyelitis through clinical assessment, prescription of biological workup (CBC + CRP + PCT + blood cultures) and MRI, and urgent referral to specialized infectious diseases and orthopedic surgery teams for bone biopsy, targeted antibiotic therapy and surgical treatment of complicated forms. Consultations are available at several points of service in Quebec, as well as via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is provided for information purposes only and does not replace the advice of a physician, infectious disease specialist or orthopedic surgeon. Osteomyelitis is a serious infection requiring specialized medical and surgical management to avoid chronicity and irreversible complications.
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