Overview
Definition:
Osteomyelitis is an infection of the bone, typically bacterial, causing inflammation and potential bone destruction
In children, it most commonly affects long bones
Prompt diagnosis and treatment are crucial to prevent chronic infection and skeletal deformities.
Epidemiology:
The incidence in developed countries is estimated to be 1 in 5,000 children annually
Staphylococcus aureus is the most common causative pathogen, accounting for over 50% of cases
Streptococcus pyogenes and Streptococcus pneumoniae are also significant
Neonates may be affected by Gram-negative bacilli
Hematogenous spread is the most common route of infection.
Clinical Significance:
Untreated or inadequately treated osteomyelitis can lead to significant morbidity, including chronic bone pain, recurrent infections, limb length discrepancy, deformities, and in severe cases, sepsis and death
Early recognition and appropriate management, including a judicious switch to oral therapy, are vital for optimal outcomes and patient well-being.
Clinical Presentation
Symptoms:
Fever, often high-grade
Severe localized bone pain, aggravated by movement
Limp or refusal to bear weight on the affected limb
Irritability and malaise in younger children
Swelling, erythema, and warmth over the affected bone
In neonates, symptoms may be nonspecific, including lethargy, poor feeding, and irritability.
Signs:
Tenderness to palpation over the affected bone
Localized swelling and erythema
Reduced range of motion in the adjacent joint
Limp or inability to ambulate
Signs of systemic illness (fever, tachycardia)
In neonates, signs can be subtle, including pseudoparalysis of an affected limb.
Diagnostic Criteria:
Diagnosis relies on a combination of clinical, laboratory, and imaging findings
The modified Waldvogel criteria include definitive (microbiological proof), probable (clinical, lab, and imaging), and possible (clinical and lab findings) categories
Radiographic evidence of bone destruction or periosteal reaction is usually seen after 7-10 days of illness.
Diagnostic Approach
History Taking:
Detailed history of onset, duration, and character of pain
History of trauma, recent infections (e.g., skin, respiratory, urinary), or bacteremia
Immunocompromised status
Travel history
Recent antibiotic use
Red flags: acute onset of severe bone pain, fever, refusal to bear weight, and signs of systemic illness.
Physical Examination:
Thorough examination of the affected limb and adjacent joints
Palpation for tenderness, swelling, and warmth
Assessment of range of motion
Examination for skin lesions or signs of trauma
Assessment of vital signs and systemic examination for signs of sepsis.
Investigations:
Laboratory: Complete blood count with differential (leukocytosis, elevated ESR and CRP)
Blood cultures (essential to identify pathogen)
Bone aspiration or biopsy for Gram stain, culture, and sensitivity (gold standard)
Imaging: Plain radiographs (may show periosteal reaction, osteolysis after 7-10 days)
Ultrasound (useful for superficial bones, soft tissue collections)
Technetium-99m bone scan (highly sensitive for early detection of infection)
MRI (most sensitive and specific for early diagnosis, extent of disease, and complications like abscesses).
Differential Diagnosis:
Septic arthritis (involves the joint)
Transient synovitis
Cellulitis
Trauma (fracture, contusion)
Juvenile idiopathic arthritis
Bone tumors (e.g., osteosarcoma, Ewing sarcoma)
Hematoma
Osteoid osteoma
Rheumatologic conditions.
Management
Initial Management:
Empirical antibiotic therapy should be initiated as soon as possible after obtaining blood cultures and aspiration/biopsy specimens
Pain management with analgesics
Immobilization of the affected limb may be necessary.
Medical Management:
Antibiotic selection depends on the suspected pathogen and local resistance patterns
For suspected S
aureus, vancomycin or clindamycin is often used initially, followed by targeted therapy based on sensitivities
For Gram-positives, nafcillin or oxacillin (if MSSA) or vancomycin (if MRSA) is preferred
For Gram-negatives, ceftriaxone or cefotaxime
Initial IV therapy for at least 48-72 hours is standard
Transition to oral therapy is considered when clinical improvement is evident, fever subsides, inflammatory markers (ESR, CRP) are declining, and pain is improving
Oral agents should have high bioavailability, good bone penetration, and cover the identified pathogen
Examples: Flucloxacillin (50-100 mg/kg/day divided q6-8h), Clindamycin (10-20 mg/kg/day divided q6-8h), Cefalexin (50-100 mg/kg/day divided q6-8h), Trimethoprim-sulfamethoxazole (15-20 mg/kg/day divided q12h for MRSA coverage)
Duration of therapy is typically 4-6 weeks, but may be longer depending on clinical response and imaging findings
Oral therapy usually lasts for the remaining duration after IV course
The total duration is often guided by normalization of inflammatory markers and resolution of radiographic changes
Pediatric guidelines recommend a total course of 4-6 weeks
Oral switch is typically considered after 5-7 days of IV therapy when clinically stable.
Surgical Management:
Indications include failure to respond to medical management, presence of a large bone abscess requiring drainage, or pathological fracture
Surgical options include incision and drainage of abscesses, debridement of necrotic bone, and management of pathological fractures.
Supportive Care:
Nutritional support
Physiotherapy to maintain range of motion and prevent contractures
Psychosocial support for the child and family
Close monitoring of vital signs, pain, and inflammatory markers.
Complications
Early Complications:
Spread of infection to adjacent joints (septic arthritis)
Soft tissue abscess formation
Bacteremia and sepsis
Pathological fracture
Compartment syndrome
Osteonecrosis.
Late Complications:
Chronic osteomyelitis
Recurrent infections
Growth disturbances and limb length discrepancy
Deformity
Osteoarthritis of adjacent joints
Osteonecrosis
Persistent bone pain.
Prevention Strategies:
Prompt diagnosis and appropriate, aggressive antibiotic therapy
Effective surgical drainage when indicated
Careful monitoring for signs of treatment failure or complications
Educating parents on recognizing early signs of infection.
Prognosis
Factors Affecting Prognosis:
Age of the patient (younger children generally have better outcomes)
Delay in diagnosis and treatment
Virulence of the pathogen
Extent of bone involvement
Presence of complications (e.g., abscess, joint involvement)
Responsiveness to initial antibiotic therapy
Appropriateness of antibiotic choice and duration
Successful surgical intervention when needed.
Outcomes:
With prompt and appropriate treatment, the prognosis for pediatric osteomyelitis is generally good, with a high rate of cure and minimal long-term sequelae
However, delayed treatment or complications can lead to chronic osteomyelitis, growth disturbances, and functional impairment.
Follow Up:
Regular follow-up appointments are essential for at least 6-12 months after completion of therapy
This includes clinical assessment of pain, function, and weight-bearing
Serial inflammatory markers (ESR, CRP) should be monitored
Repeat imaging (radiographs or MRI) may be indicated if there is clinical suspicion of recurrence or if significant bone damage occurred
Monitoring for long-term skeletal growth and development.
Key Points
Exam Focus:
The transition from IV to oral therapy for pediatric osteomyelitis is a critical management decision
High-bioavailability oral agents (e.g., clindamycin, flucloxacillin, cefalexin) are preferred
Criteria for switch include clinical stability, defervescence, and declining inflammatory markers
Total therapy duration is typically 4-6 weeks
Staphylococcus aureus is the most common pathogen.
Clinical Pearls:
Always obtain blood cultures and bone aspirate/biopsy before starting antibiotics if possible
Early MRI can be invaluable for diagnosis and assessing extent of disease, especially in cases with vague presentations
Consider clindamycin for MRSA coverage and its excellent bone penetration, especially in purulent lesions
Monitor inflammatory markers closely during oral therapy to detect relapse.
Common Mistakes:
Delaying antibiotic initiation due to waiting for definitive cultures
Inadequate duration of antibiotic therapy
Using oral antibiotics with poor bioavailability for prolonged treatment
Failure to consider surgical drainage for abscesses
Misinterpreting imaging findings in early stages of infection
Not adequately considering differential diagnoses, especially bone tumors.