# CIM Case: Chronic Osteomyelitis in Child ## Clinical Scenario **Patient:** 12-year-old girl **Presentation:** 3 months post closed reduction of proximal humerus fracture treated with hanging cast, ongoing pain and now developing intermittent discharge from anterior shoulder **Relevant history:** Initially uncomplicated fracture from netball injury, treated in ED with closed reduction and hanging cast for 6 weeks, slow to recover with persistent dull ache, low-grade fevers (37.8°C) noted at home, no antibiotic treatment previously **Examination findings:** - Sinus tract over anterolateral proximal humerus with purulent discharge - Surrounding erythema and induration - Reduced range of motion (elevation 90°, external rotation 20°) - No acute systemic sepsis - Afebrile currently - Axillary lymphadenopathy - Otherwise well, no weight loss --- ## Investigations Provided ### Laboratory Results | Test | Result | Normal Range | Interpretation | |------|--------|--------------|----------------| | Hb | 112 g/L | 115-155 g/L | ↓ Mild anaemia (chronic infection) | | WCC | 10.2 ×10⁹/L | 4-11 ×10⁹/L | Normal (common in chronic infection) | | Platelets | 380 ×10⁹/L | 150-400 ×10⁹/L | Upper normal (reactive) | | CRP | 42 mg/L | <5 mg/L | ↑ Elevated | | ESR | 65 mm/hr | <10 mm/hr | ↑ Significantly elevated | | Albumin | 32 g/L | 35-50 g/L | ↓ Low (chronic inflammation) | ### Imaging **Image 1: AP and Lateral Radiographs of Right Humerus** **Radiological features:** - Fracture healed in acceptable alignment - Periosteal reaction with cortical irregularity around proximal metaphysis - Central area of lucency with sclerotic rim (Brodie's abscess/sequestrum) - New bone formation laterally (involucrum) - Cloaca visible (draining tract through cortex) - No pathological features of tumour **Image 2: MRI of Right Proximal Humerus** **MRI findings:** - 3cm intramedullary abscess in proximal humeral metaphysis - Cortical breach with soft tissue extension - Surrounding bone oedema on STIR sequences - Sinus tract extending to skin surface - No joint involvement - Physis appears intact ## Questions & Model Answers **Diagnosis:** Chronic post-traumatic osteomyelitis of the proximal humerus **Definition of Chronic Osteomyelitis:** - Bone infection persisting >6 weeks OR - Presence of sequestrum, sinus, or necrotic bone **Pathophysiology of Chronic Osteomyelitis:** **Sequence of Events:** | Stage | Pathological Process | |-------|---------------------| | **Acute infection** | Bacteria enter bone (haematogenous or direct inoculation) | | **Ischaemia** | Raised intraosseous pressure compromises blood supply | | **Necrosis** | Avascular bone dies, forms sequestrum | | **Walling off** | Fibrous tissue and new bone (involucrum) form around dead bone | | **Drainage** | Cloaca forms through involucrum, sinus to skin develops | | **Chronicity** | Bacteria protected within dead bone and biofilm | **Key Pathological Features:** | Feature | Description | |---------|-------------| | **Sequestrum** | Dead, avascular bone harbouring bacteria | | **Involucrum** | New reactive bone surrounding sequestrum | | **Cloaca** | Opening in involucrum allowing drainage | | **Sinus tract** | Channel from bone to skin surface | | **Biofilm** | Bacterial community protected from antibiotics and immune system | **Why This Patient Developed Chronic Osteomyelitis:** - Fracture haematoma = nidus for infection - May have had subclinical contamination at time of injury - Alternatively, haematogenous seeding of fracture site - Early signs (low-grade fever, slow healing) were missed - Without early treatment, progressed to chronic infection **Common Organisms:** | Organism | Features | |----------|----------| | **Staphylococcus aureus** | Most common (70-80%), biofilm-forming | | **MRSA** | Increasing, consider if risk factors | | **Streptococcus species** | Less common, more indolent | | **Kingella kingae** | Young children (<5 years) | | **Gram-negative organisms** | Pseudomonas (puncture wounds), Salmonella (sickle cell) | > **Consultant Tip:** Once a sequestrum forms, antibiotics alone won't work. The dead bone protects bacteria and must be surgically removed. **Cierny-Mader Classification:** **Anatomic Type (based on bone involvement):** | Type | Description | This Patient | |------|-------------|--------------| | **I** | Medullary (endosteal only) | - | | **II** | Superficial (cortical surface) | - | | **III** | Localised (full thickness, stable bone) | ✓ Most likely | | **IV** | Diffuse (circumferential, unstable) | - | **Physiologic Host Class:** | Class | Description | This Patient | |-------|-------------|--------------| | **A** | Normal host, no compromise | ✓ Most likely | | **B-local** | Local compromising factors (scarring, venous stasis) | - | | **B-systemic** | Systemic compromise (diabetes, immunosuppression) | - | | **B-combined** | Both local and systemic | - | | **C** | Treatment worse than disease | - | **This Patient: Cierny-Mader Type III-A** (localised, normal host) **Investigation Strategy:** **Laboratory:** | Test | Purpose | |------|---------| | FBC | Anaemia of chronic disease, WCC often normal | | CRP | Acute phase marker, follows treatment response | | ESR | Chronic inflammation marker, slower to change | | Albumin | Nutritional status, affects healing | | Cultures (deep) | Organism identification, sensitivities | | Blood cultures | Usually negative in chronic OM | **Imaging:** | Modality | Findings | |----------|----------| | **X-ray** | Sequestrum, involucrum, cloaca, periosteal reaction | | **MRI** | Gold standard - bone marrow oedema, abscess, soft tissue extent, guides debridement | | **CT** | Bony anatomy, sequestrum mapping (surgical planning) | | **Nuclear medicine** | WBC scan or PET-CT if diagnosis unclear | **Tissue Diagnosis:** | Investigation | Importance | |---------------|------------| | **Deep tissue culture** | NOT swab - obtain at debridement | | **Multiple samples** | 3-5 samples from different areas | | **Histopathology** | Confirms chronic infection, excludes tumour | | **Hold antibiotics** | 2 weeks before sampling if possible | > **Consultant Tip:** Never rely on superficial swab cultures. Deep tissue samples at surgery are essential for accurate organism identification. **Principles of Chronic Osteomyelitis Surgery:** **The "5 D's" of Management:** 1. **Diagnosis** - Tissue culture, histology, identify organism 2. **Debridement** - Remove ALL dead and infected tissue 3. **Dead space management** - Fill defects, prevent reinfection 4. **Drug delivery** - Antibiotics (local and systemic) 5. **Definitive soft tissue coverage** - Achieve wound healing **Surgical Debridement Technique:** **Approach:** - Extensile approach to visualise all infected bone - Excise sinus tracts completely (send for culture) - Consider staged procedure if extensive **Debridement Steps:** | Step | Technique | |------|-----------| | 1. Expose infection | Wide surgical exposure | | 2. Remove sequestrum | Identify and excise all dead bone | | 3. Debride to bleeding bone | "Paprika sign" - punctate bleeding indicates viable bone | | 4. Lavage | High-volume pulse lavage (minimum 6-9 litres) | | 5. Take samples | 3-5 deep tissue cultures, histology | | 6. Address dead space | Beads, cement, or leave open | **The "Paprika Sign":** - After excision, drill multiple holes in remaining cortex - Viable bone bleeds from drill holes (like paprika sprinkled on white surface) - If no bleeding, bone is avascular and must be removed - Continue until all remaining bone shows punctate bleeding **Dead Space Management Options:** | Method | Indication | |--------|------------| | **Antibiotic beads** | Temporary spacer, local antibiotic delivery | | **PMMA cement with antibiotics** | Larger defects, load-bearing areas | | **Antibiotic-impregnated calcium sulphate** | Biodegradable, single stage | | **Muscle flap** | Vascularised coverage, fights infection | | **Bone graft (staged)** | After infection controlled | **This Patient's Surgical Plan:** 1. Extensile anterior approach to proximal humerus 2. Excise sinus tract 3. Unroof abscess cavity 4. Debride to paprika sign 5. Multiple tissue samples 6. Antibiotic bead insertion 7. Wound vacuum or delayed closure > **Consultant Tip:** The paprika sign is your guide. If bone doesn't bleed, it won't heal. Be aggressive with debridement - underdebridement is the commonest cause of treatment failure. **Antibiotic Principles in Chronic Osteomyelitis:** **Key Concepts:** - Culture-directed therapy is ESSENTIAL - Empiric treatment only until cultures return - Prolonged duration required (6+ weeks minimum) - Consider biofilm penetration **Empiric Antibiotic Selection (Pre-culture):** | Scenario | Regimen | |----------|---------| | **Standard** | Flucloxacillin 50mg/kg/dose QID + Rifampicin 10mg/kg BD | | **Penicillin allergy** | Vancomycin + Rifampicin | | **MRSA risk** | Vancomycin + Rifampicin | | **Gram-negative suspected** | Add gentamicin or ciprofloxacin | **Culture-Directed Therapy:** | Organism | First Line | Alternative | |----------|------------|-------------| | **MSSA** | Flucloxacillin + Rifampicin | Cephalexin, clindamycin | | **MRSA** | Vancomycin + Rifampicin | Daptomycin, linezolid | | **Streptococcus** | Penicillin or ceftriaxone | Vancomycin | | **Gram-negative** | Ciprofloxacin (if sensitive) | Ceftazidime, meropenem | **Why Rifampicin?** - Excellent biofilm penetration - Good bone concentration - **Must be combined** with another agent (resistance develops rapidly if used alone) - Side effects: hepatotoxicity, drug interactions **Duration of Therapy:** | Phase | Duration | |-------|----------| | **IV therapy** | 2-4 weeks (until clinical improvement) | | **Oral therapy** | 4-8 weeks (total 6-12 weeks minimum) | | **Monitoring** | CRP weekly, clinical review | **Oral Agents with Good Bone Penetration:** - Fluoroquinolones (ciprofloxacin, moxifloxacin) - Rifampicin - Clindamycin - Linezolid (expensive, side effects with prolonged use) - Trimethoprim-sulfamethoxazole **Monitoring Treatment Response:** | Parameter | Expected Response | |-----------|-------------------| | CRP | Falls 50% by 1 week, normalises by 3-4 weeks | | ESR | Slower to fall, may take months | | Clinical | Pain improves, sinus heals | | Imaging | MRI at 6-8 weeks (oedema may persist) | > **Consultant Tip:** Rifampicin is key for biofilm penetration but NEVER use alone. Always combine with another active agent. In children, fluoroquinolones are increasingly used despite traditional concerns about cartilage. **Dead Space Management:** **Why Dead Space Matters:** - Empty cavity fills with haematoma - Haematoma = ideal bacterial culture medium - Leads to reinfection if not addressed **Options for Dead Space:** **1. Antibiotic Beads (PMMA + Antibiotics):** **Technique:** - Mix antibiotic powder into bone cement (PMMA) - Form beads on wire or thread - Pack into cavity after debridement - Remove at 2-4 weeks (second stage) **Antibiotic Choices for Beads:** - Gentamicin (4.8g per 40g cement) - most common - Vancomycin (4g per 40g cement) - for MRSA - Tobramycin - alternative **2. Antibiotic Cement Spacer:** - For larger defects - Custom-moulded to fit cavity - Maintain space for later bone grafting **3. Bioabsorbable Antibiotic Carriers:** - Calcium sulphate beads with antibiotics - Resorb over 4-8 weeks - Single-stage procedure possible - No second surgery for removal **4. Muscle Flap Transfer:** - Vascularised tissue fills dead space - Brings blood supply (fights infection) - Options: local rotational flaps, free flaps - Proximal humerus: pectoralis major, latissimus dorsi **Soft Tissue Coverage Options:** | Method | Indication | |--------|------------| | **Primary closure** | Small wounds, healthy tissue | | **Delayed primary closure** | Moderate contamination, observe first | | **VAC (negative pressure)** | Large wounds, promotes granulation | | **Split-thickness skin graft** | Granulating bed, non-weight-bearing | | **Local flap** | Moderate defects, nearby tissue available | | **Free flap** | Large defects, poor local tissue | **This Patient's Options:** - After debridement: Antibiotic beads + VAC - Return at 48-72 hours for inspection - If clean: Remove beads, consider calcium sulphate beads - If granulating well: Delayed primary closure or skin graft - Rarely needs flap for proximal humerus (good soft tissue) > **Consultant Tip:** VAC therapy has revolutionised wound management in osteomyelitis. It promotes granulation tissue formation and can convert a wound that needs a flap into one that can be grafted. **Complications of Chronic Osteomyelitis Treatment:** **Early Complications:** | Complication | Prevention/Management | |--------------|----------------------| | **Persistent/recurrent infection** | Adequate debridement, culture-directed antibiotics | | **Fracture (through weakened bone)** | Protect limb, may need fixation | | **Wound breakdown** | Tension-free closure, VAC if needed | | **Antibiotic toxicity** | Monitor renal function, hepatic function | | **Growth disturbance** | Risk if physis involved (this patient's physis appears intact) | **Late Complications:** | Complication | Notes | |--------------|-------| | **Recurrence** | Up to 30% at 2 years if inadequate debridement | | **Chronic pain** | May persist even after cure | | **Joint stiffness** | From scarring, prolonged immobilisation | | **Leg length discrepancy** | If physis affected in growing child | | **Malignancy (Marjolin's ulcer)** | SCC arising in chronic sinus - rare, after decades | | **Amputation** | Last resort for refractory cases, life-threatening sepsis | **Prognostic Factors:** | Favourable | Unfavourable | |------------|--------------| | Normal host (Cierny A) | Compromised host (B or C) | | Localised disease (Type I-III) | Diffuse disease (Type IV) | | Single organism | Polymicrobial | | Sensitive organism | MRSA, resistant organisms | | First presentation | Recurrent after treatment | | Good soft tissue | Poor soft tissue coverage | | Child (healing potential) | Adult/elderly | **This Patient's Prognosis:** - Cierny-Mader III-A (localised, normal host) - FAVOURABLE - Child with good healing potential - First presentation - Good soft tissue - Expected success rate: 80-90% with adequate treatment **Follow-up Protocol:** | Time | Assessment | |------|------------| | 2 weeks | Wound check, CRP trending down | | 6 weeks | Clinical assessment, X-ray, CRP/ESR | | 3 months | Clinical and radiographic review | | 6 months | Ensure no recurrence | | 12 months | Final assessment | | Long-term | PRN if symptoms recur | **Markers of Cure:** - Healed wound/no sinus - No pain - Normal CRP - No radiographic progression - Functional limb > **Consultant Tip:** Quote 80-90% cure rate for localised disease in normal hosts treated surgically. The key determinant of success is adequacy of initial debridement. Underdebridement leads to recurrence. --- ## Key Teaching Points ### Pattern Recognition **This pattern suggests Chronic Osteomyelitis:** - Prior bone insult (fracture, surgery, haematogenous) - Prolonged symptoms >6 weeks - Draining sinus tract - Low-grade systemic features (mild anaemia, raised ESR/CRP) - Imaging showing sequestrum, involucrum, cortical irregularity **Distinguish from Acute Osteomyelitis:** | Feature | Acute | Chronic | |---------|-------|---------| | Duration | <2 weeks | >6 weeks | | Systemic symptoms | High fever, toxic | Low-grade, may be afebrile | | WCC | Elevated | Often normal | | Imaging | Soft tissue swelling, later periosteal reaction | Sequestrum, involucrum, cloaca | | Treatment | Antibiotics often sufficient | Surgery almost always required | ### Critical Management Points 1. **Deep tissue culture is essential** - never treat on swab alone 2. **Debride to paprika sign** - all remaining bone must bleed 3. **Rifampicin for biofilm** - but never as monotherapy 4. **Manage dead space** - beads, cement, or flap 5. **Prolonged antibiotics** - 6-12 weeks minimum 6. **CRP tracks response** - ESR slower to change 7. **Second-look if needed** - don't hesitate to re-debride --- ## Common Examiner Follow-ups **Q: "What is the role of hyperbaric oxygen therapy?"** Hyperbaric oxygen therapy (HBOT): - Adjunctive therapy for refractory chronic osteomyelitis - Increases tissue oxygen tension - Enhances neutrophil bacterial killing - Promotes angiogenesis in ischaemic tissue - Potentiates some antibiotics - Evidence mixed but may be considered for: - Refractory cases after multiple debridements - Compromised hosts (diabetes, vascular disease) - Extensive involvement - Not first-line treatment --- **Q: "How would you manage a growth disturbance from physeal involvement?"** If physis is involved and damaged: - Monitor for growth arrest with serial X-rays - Compare limb lengths clinically and radiographically - If bar forms: Consider bar excision if <50% physis and 2+ years growth remaining - If significant LLD predicted: Contralateral epiphysiodesis or limb lengthening - For this patient: Physis appears intact on MRI - monitor but low risk --- **Q: "What if this patient had a pathological fracture through the infected bone?"** Management of pathological fracture through osteomyelitis: - **Priority:** Treat infection AND stabilise bone - **Debridement** as usual - **Stabilisation options:** - External fixation (preferred - keeps hardware outside infection) - Plate fixation with antibiotic cement coating - Antibiotic-coated intramedullary nail (newer) - **Bone grafting** after infection controlled (staged) - **Avoid standard internal fixation** without addressing infection - May need longer antibiotics and multiple stages --- **Q: "What is the role of PET-CT in osteomyelitis?"** FDG PET-CT role: - Differentiates infection from tumour (both can be hot) - Detects extent of infection not seen on MRI - Useful when MRI contraindicated (metalwork, pacemaker) - Can detect multifocal disease - Monitors treatment response - Limitations: radiation exposure, availability, cost, less anatomical detail than MRI --- ## Related Topics - Acute Paediatric Osteomyelitis - Brodie's Abscess - Septic Arthritis - Prosthetic Joint Infection - Antibiotic Bone Penetration - Negative Pressure Wound Therapy