Authors: Zac Crenshaw, DO (EM Resident Physician, Mizzou – Columbia, MO); Jessica Pelletier, DO, MHPE (Assistant Professor of EM/Assistant Residency Director, Mizzou – Columbia, MO) // Reviewed by: Sophia Görgens, MD (EM Physician, BIDMC, MA); Cassandra Mackey, MD (Assistant Professor of Emergency Medicine, UMass Chan Medical School); Alex Koyfman, MD (@EMHighAK); Brit Long, MD (@long_brit)
Welcome to EM@3AM, an emDOCs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.
A 2-year-old female with a past medical history of failure to thrive presents to the ED with her mother for evaluation of right arm pain. The mother states that the patient was recently started on mupirocin for a spot on her right forearm the day prior. Since then, the mother states she has noticed a “hard spot” on the patient’s right clavicle. Mother denies any recent trauma or falls and also reports a temperature at home of 37.8° C. Per chart review, the patient was recently discharged a week prior after a 6-day admission for failure to thrive.
Initial vital signs include temperature 37.0° C, HR 136 bpm, RR 32 breaths/minute, and blood pressure of 99/57 mmHg. The head is atraumatic and normocephalic. Auscultation of the heart reveals a regular rate and rhythm, and lungs are clear to auscultation bilaterally. Physical exam is notable for guarding of the right upper extremity with induration overlying the proximal right clavicle with minimal surrounding erythema. There are no step-offs or bruising throughout the bilateral upper extremities. The patient has 2+ bilateral radial pulses. There is decreased active range of motion of the right shoulder which appears to be secondary to pain. She has full range of motion of all other joints.
X-ray shows the following:
Question: What is the likely diagnosis?
Answer: Pediatric Osteomyelitis
Background:
- Osteomyelitis is defined as bone inflammation secondary to microbial infection typically involving the metaphysis1
Etiology:
- Osteomyelitis can be divided into 3 sub-categories based on time frame2
- Acute (less than two weeks)
- Subacute (between two weeks and three months)
- Chronic (more than three months)
- Osteomyelitis has three common mechanisms of infection3
- Pathogen’s dissemination via the blood (hematogenous)
- Hematogenous spread is most frequently seen in children
- Extension by contiguity
- Penetration of the infectious agent (traumatic)
- Pathogen’s dissemination via the blood (hematogenous)
- A common microbiological agent of osteomyelitis is Staphylococcus aureus, a Gram-positive coccus that commonly colonizes the airways and skin2
Epidemiology:
- Incidence of pediatric osteomyelitis is estimated between 1.2 and 13 cases per 100,00 children per year1
- Osteomyelitis more commonly affects children younger than 5 years of age with boys being affected nearly twice more commonly than girls. This is thought to be secondary to increased microtrauma for boys1
- In pediatric patients long bones (femur, tibia) are more commonly infected nearing 75% of the time. Short, non-tubular bones, and vertebrae are involved only 25% of the time1
- Staphylococcus aureus, mainly methicillin-sensitive strains (MSSA), are responsible for up to 70-90% of pediatric cases3
- Infections caused by K. kingae have shown to be milder, with fewer laboratory alterations and less systemic involvement2
- Pseudomonas infections are typically seen in trauma to the plantar aspect of the foot, more commonly when shoes are penetrated2
Clinical Presentation:
- Osteomyelitis typically presents with acute non-traumatic bony pain, which is often accompanied by fever
- Pain is the most commonly reported symptom upon presentation (94.3%)5
- Patients also commonly report functional limitations (83.9%), focal tenderness (73.5%), and swelling (52.1%)5
- Fever (>38.0 C) is seen in 76.3%5
Evaluation:
- Physical examination
- Visualization looking for erythema
- Palpation looking for pain/point tenderness or step-off
- Range of motion of all joints
- Pulses in all extremities
- Vital signs, specifically looking for systemic signs of infection (fever)
- Pain on palpation of involved bone is the most sensitive finding (seen in 81% of cases) but is not specific4
Diagnosis:
- Workup involves a thorough physical exam, labs including ESR, CRP, CBC, and blood cultures
- CRP has a higher sensitivity than ESR
- CRP >0.8mg/dL sensitivity of 92.9, CRP >1.0 sensitivity of 91.5%, CRP >2.0 sensitivity of 83.95
- ESR >10mm/h with a sensitivity of 94.3, ESR>20 mm/h with a sensitivity of 79.05
- Median CRP of 5.2mg/dL and a median ESR of 38mm/h in pediatric osteomyelitis5
- The combination of ESR and CRP is more sensitive than either test alone (98%)6
- CRP has a higher sensitivity than ESR
- Radiographs should be obtained to rule out fracture or other musculoskeletal pathology
- MRI is the gold standard but is often not realistic in the ED setting; this can often be obtained on an inpatient basis
Figure 2. Pediatric osteomyelitis treatment algorithm.4 Adapted from: Gornitzky AL, Kim AE, O’Donnell JM, Swarup I. Diagnosis and Management of Osteomyelitis in Children: A Critical Analysis Review. JBJS Reviews. 2020 Jun;8(6):e19.00202-e19.00202.
Treatment:
- Surgical management with incision and drainage is typically indicated in the presence of associated abscess4
- Orthopedic consultation is necessary
- If osteomyelitis does not have an associated abscess, treatment involves IV antibiotics followed by at least 3 weeks of oral antibiotics4
- Empiric antibiotic therapy depends on age, degree of illness, and suspicion of MRSA infection
-
- Most recommendations suggest conversion to oral antibiotics after clinical improvement, resolution of fever, and down-trending CRP4
- Longer courses of oral antibiotics depend on the clinical picture- advanced disease, patient age, and infectious etiology
- Infectious disease consultation
- There is no gold-standard antibiotic regimen, rather therapeutic decision-making based on suspected microbiological epidemiology and local MRSA prevalence4
Prognosis:
- Complications of osteomyelitis are typically seen in the early stage with associated bacteremia leading to possible septic shock.2
- Late complications of osteomyelitis, although rare with adequate antimicrobial treatment, include:2
- Impairment of growth plate leading to difference in limb size
- Avascular necrosis of femoral head
- Pathological fractures
- Loss of function
- Recurrent infections
Pearls and Pitfalls:
- The classic presentation for osteomyelitis is bony pain with associated fever
- Boys are at higher risk than girls, and aureus is the most common bacterial cause
- The combination of ESR and CRP is the most helpful laboratory testing strategy
- MRI is the gold standard for diagnosis
- Definitive treatment involves antibiotics PLUS surgical intervention if there is an abscess
A 5-year-old boy presents to the emergency department with a fever. Which of the following, if present, would put this patient at a higher risk of osteomyelitis?
A) Factor VIII deficiency
B) Hereditary spherocytosis
C) Recently reduced closed long bone fracture
D) Sickle cell disease
Correct answer: D
Osteomyelitis is a bacterial infection of the bone typically caused by hematogenous spread of a bloodborne bacteria. About half of cases occur in the metaphysis of long bones in the legs due to low-velocity blood flow from a sharp loop of blood vessels. It is more common in male or previously healthy patients. The most commonly identified organism across all age groups is Staphylococcus aureus, although group B Streptococcus is another important cause in neonates. It presents with fever and focal bone pain in young children, although half of neonates will be afebrile and may only present with fussiness.
Neonates at higher risk for osteomyelitis include those who are premature and born to mothers with an active infection and those with a complicated delivery, skin infection, urinary tract anomalies, or a central venous catheter. Other children at risk for osteomyelitis include those with sickle cell disease, sepsis, an indwelling catheter, and immunodeficiency (e.g., due to chronic granulomatous disease). Children with sickle cell disease are at higher risk of osteomyelitis from Salmonella or Streptococcus pneumoniae. Immunocompromised patients are at higher risk of osteomyelitis from Aspergillus, Candida albicans, or mycobacteria.
Osteomyelitis is typically diagnosed with an MRI, although it can sometimes be seen on X-ray. It requires surgical input and cross-sectional imaging to determine if there is a nidus of infection that must be drained. Otherwise, the treatment is typically a long course of broad-spectrum intravenous antibiotics that cover the expected organism (e.g., vancomycin for Staphylococcus and Salmonella). Infectious disease expertise is useful as the optimum duration of treatment is not well established. Patients with septic arthritis often need an MRI, as they frequently have concomitant osteomyelitis.
Factor VIII deficiency (A) (i.e., hemophilia A) increases the risk of bleeding with minor injury, including hemarthrosis. However, it is not a known or suspected risk factor for osteomyelitis.
Hereditary spherocytosis (B) puts patients at risk for jaundice, splenomegaly, pigment gallstones, and an aplastic crisis from parvovirus, but it is not known or suspected to increase the risk of osteomyelitis.
A minor injury with associated bacteremia is associated with osteomyelitis, but a recently reduced closed long bone fracture (C) is not.
