Osteomyelitis and Septic Arthritis
Osteomyelitis and Septic Arthritis: Excerpt from Pediatric Infectious Disease
Etiology
Children are colonized with a variety of bacteria; a culture of the nasopharynx
of an asymptomatic child could yield any number of bacteria, including
Staphylococcus aureus and Streptococcus pneumoniae. Usually, these organisms reside on body surfaces with no ill effects. However,
by a process not always well defined, these colonizing bacteria enter the
bloodstream.
Once the bacteria enter the bloodstream, numerous things can occur (Fig. 2.1).
Bacteremia can be transient and resolve without sequelae; this is often the
case with viridans streptococci. Bacteremia, by its very presence in the
systemic circulation, can cause overwhelming sepsis, as is often the case with
Neisseria meningitidis. Bacteria can also be deposited in secondary sites, such as the cerebrospinal
fluid or bone.
The bones are a frequent site of secondary infection because the blood supply
takes a hairpin turn at the metaphyses of long bones, increasing the chance of
the bacteria being deposited. This secondary seeding of bones from the blood is
the major mechanism of pediatric osteomyelitis. This is in contrast to adults,
who usually acquire osteomyelitis from direct inoculation following trauma or
surgical procedures.
Pyogenic arthritis develops in a fashion similar to osteomyelitis, whereby
blood-borne organisms are deposited in the synovium of the joint space. Similar
to the long bones of children, the joint space is highly vascularized and is an
area where bacteremic organisms are readily deposited. Bacterial arthritis can
also spread from a contiguous osteomyelitis; blood vessels can deposit
infection from the metaphysis into the joint space. The organisms of septic
arthritis are similar to those of osteomyelitis.
S. aureus is the most common organisms, followed by S. pneumoniae, Kingella kingae, and group A streptococcus.
Presentation
The hallmark of pediatric osteomyelitis or septic arthritis is fever and
localized pain. In the toddler whose verbal skills may not be sufficiently
developed, the presentation may be simply fever and refusal to walk. It is for
this reason that for many clinicians, fever and refusal to walk in a child
indicates osteomyelitis or septic arthritis until proven otherwise. Septic
arthritis of the hip is of particular concern to pediatricians because this
joint space cannot be visualized directly on physical examination.
Diagnosis
Evaluation
When facing the clinical condition of the febrile child who is not walking, it
is necessary to pursue a logical clinical and laboratory evaluation. A complete
physical examination is mandatory. Point tenderness should be sought in an
attempt to localize potential infected areas. A careful examination should
always include full range of motion of the hips.
All joints that appear swollen and erythematous should be aspirated with fluid
sent for Gram stain, culture, and white blood cell count. If purulent fluid is
present or an aspirate reveals greater than 100,000 white blood cells/m
3 or positive Gram stain, the diagnosis of septic arthritis is made.
If point tenderness is elicited, plain films of the area should be done. Changes
on plain films from osteomyelitis are often not apparent for at least 14 days;
the real purpose of plain films is to rule out any other reason for the
clinical presentation, such as an occult fracture or foreign body. Complete
blood counts, sedimentation rate, and blood cultures are also useful. Although
only 50% of patients with osteomyelitis have elevations in their white blood
cell count, 90% of patients with osteomyelitis or septic arthritis have
elevation in the sedimentation rate or C-reactive protein. Given the mechanism
of the disease in pediatric osteomyelitis, blood cultures should be obtained
and are positive in up to 30% of cases.
Several radiographic studies can be used in the further evaluation of pediatric
osteomyelitis. Radionucleotide bone scan has been a traditional exam that shows
increased uptake around infected bone (Fig. 2.3). There is increasing
experience using magnetic resonance imaging (MRI) in visualizing infected bone
and bone marrow for the diagnosis of osteomyelitis. In centers in which there
is expertise in the use of MRI, it is often a front-line study. It should be
noted that MRI is sensitive, but not specific. Although it is very helpful in
documenting abnormalities in bone, bone marrow, or soft tissue, it is not
specific in determining the etiology of these changes. Appearance of bone and
bone marrow in infection, trauma, or even infarction following sickle cell
crisis can appear similar. Interpretation of MRI findings should always be done
with the clinical context in mind (Figs. 2.4 and 2.5).
Management
Antibiotic Therapy for Pediatric Osteomyelitis
After the diagnosis of pediatric osteomyelitis is made, empiric therapy is
begun. The major organism for pediatric osteomyelitis is
S. aureus. It is increasingly appreciated that a large proportion of community-acquired S. aureus is methicillin resistant. Once seen only as a nosocomial infection, some
communities report that up to 70% of
S. aureus infections are resistant to methicillin. When confronted with S. aureus disease, the pediatrician can no longer assume that the organism will be
sensitive to traditional antistaphylococcal medications such as nafcillin or
first-generation cephalosporins. Community-acquired methicillin-resistant
S. aureus (MRSA) is often sensitive to clindamycin and trimethoprim-sulfamethoxazole.
Some clinicians are now empirically using clindamycin for initial treatment of
community-acquired
S. aureus disease; this usually covers both methicillin-susceptible and
methicillin-resistant strains.
Although community-acquired MRSA is often initially susceptible to clindamycin,
it has been noted that MRSA sensitive to clindamycin but resistant
to erythromycin has the potential to develop clindamycin resistance. The
specific test for the presence of inducible clindamycin resistance is the
erythromycin induction (D) test. Although it is known that D-testing can detect
inducible clindamycin resistance in a large percentage of MRSA isolates, it is
not clear whether this
in vitro test predicts clinical failure of clindamycin. There are scattered case reports
of actual clinical failure in patients with a positive D test in whom
clindamycin was used; it is advised that long-term clindamycin treatment for
MRSA, such as that given for osteomyelitis, be approached with caution.
Alternatives for long-term antibiotic therapy for MRSA infections include
vancomycin and linezolid.
Before the development of the Haemophilus influenzae vaccine, this organism was also a frequent cause of pediatric osteomyelitis and
septic arthritis. Despite the decline in
H. influenzae disease, gram-negative organisms still play a role in pediatric osteomyelitis. K. kingae, a fastidious hemolytic gram-negative bacilli, has emerged in recent years as
an invasive pathogen in children. Osteomyelitis and septic arthritis are the
most common presentations of invasive
K. kingae infections in children. Recent studies have suggested that about 20% of septic
arthritis and osteomyelitis may be due to this organism. Some series have
reported that
K. kingae is the most common cause of septic arthritis in children younger than 2 years,
being the causative agent in almost one half of cases. Thought to be a normal
part of the oral flora in children, this pathogen gains access to the
bloodstream in a manner similar to
S. aureus. It is postulated that disruption of the respiratory or oral mucosa allows
colonizing bacteria to enter the bloodstream. Preceding stomatitis is thought
to play a role in the development of bacteremia and subsequent infection. Bone
infection caused by
K. kingae can be present in unusual locations, such as metatarsal bones and the epiphysis
of long bones.
Kingella is a fastidious aerobic pathogen that may not grow on standard agar; direct
inoculation of an osteoarticular aspirate into blood culture bottles has been
reported to improve the yield of cultures. Polymerase chain reaction
amplification of synovial fluid has also been employed successfully in
identifying the organism.
K. kingae remains highly susceptible to many antibiotics, including third-generation
cephalosporins.
Salmonella species are other gram-negative organisms that can cause osteomyelitis, particularly in patients with sickle cell anemia. It is for this
reason that
therapy with clindamycin, nafcillin, or a first-generation cephalosporin,
combined with a third-generation cephalosporin (for optimal gram-negative
coverage), is often used as empiric treatment of osteomyelitis until culture
results are available.
Duration of Therapy
Early studies pointed to a higher relapse rate in patients treated for 3 weeks
or less. Chronic infection has also been reported to develop more frequently in
patients receiving only 3 weeks of therapy as compared with patients receiving
therapy for 4 weeks or longer. Many clinicians believe that the minimum
duration of treatment is 4 weeks and often continue treatment for as long as 6
weeks.
The monitoring of therapy using the sedimentation rate and C-reactive protein
has been advocated. In children with septic arthritis, it is thought that the
serum C-reactive protein peaks within 48 hours after treatment and normalizes
in about 1 week. In contrast, the sedimentation rate may continue to increase
despite effective treatment until day 5 and may remain elevated for more than 1
month. It has been recommended that the C-reactive protein be measured about 2
days after treatment is begun. Normalization suggests effective therapy.
Treatment is often continued until the sedimentation rate returns to normal
values; this usually coincides with about a 1-month duration of therapy. An
increasing C-reactive protein level or persistently elevated sedimentation rate
can herald the need for surgical drainage. If, after 1 month of therapy, the
repeated sedimentation rate is greater than 30 mm/h, a repeat MRI can be
obtained to determine the need for surgery. Antibiotics can then continue for
an additional 3 weeks, with repeat MRI and sedimentation rate done at that
time.
Intravenous versus Oral Antibiotics
Traditionally, it was thought that serious bacterial infections such as
osteomyelitis required intravenous antibiotics. In the early 1980s, studies
examined the efficacy of oral treatment of pediatric osteomyelitis. These
studies used the serum bactericidal titer (SBT) or Schlichter
’s test. This test is a modification of the MIC test. Patients with proven S. aureus osteomyelitis are given high-dose oral therapy, often 100 mg/kg per day of oral
cephalexin. Serial dilutions are made from peak and trough serum samples. To
these serial dilutions, an aliquot of the patient
’s infecting organism is added; the dilutions remaining clear after 24 hours of
incubation is then plated on agar plates. The dilution at which bacteria fail
to grow on agar plates is the peak and trough bactericidal titer (Fig. 2.6).
Prospective studies have determined that children with acute hematogenous
osteomyelitis with a peak SBT of greater than or equal to 1:16 and a trough of
greater than or equal to 1:2 achieve bacteriologic and clinical cure. Following
these studies, many physicians advocate the use of oral antibiotics if the
following conditions are met: (a) an organism is isolated, (b) adequate peak
and trough SBTs can be obtained on oral therapy, and (c) compliance with oral
therapy can be assured.
During the past 5 years, numerous reports have questioned the necessity of SBTs
during oral therapy for osteomyelitis. Small series have reported good outcome
in patients treated with oral antibiotics without confirmatory SBT measurement.
To this day, there is great variation in clinical practice; some institutions
will not use oral therapy unless a pathogen is isolated and adequate SBTs can
be documented. Some clinicians use oral therapy only if they are sure of the
infecting organism, but do not think that SBTs are necessary. It is likely that
the pediatrician caring for a child with osteomyelitis will have to make a
case-by-case decision regarding what is the best mode of treatment for that
particular child.
Antibiotic Therapy for Pediatric Septic Arthritis
Septic arthritis in joints other than the hip may not require surgical
intervention, although repeated aspirations are sometimes used if fluid
reaccumulates. Failure of septic arthritis to respond to appropriate antibiotic
therapy should always lead to the consideration for surgical drainage. As in
osteomyelitis, antibiotic therapy is traditionally given for at least 4 weeks.
As in osteomyelitis, there is increasing experience in switching patients to
oral antibiotic therapy after their physical exam has normalized. Many centers
use an SBT with a peak titer of 1:16 as the level correlated with bacteriologic
eradication and clinical cure.
Chronic Osteomyelitis
Although the increased duration of effective therapy has reduced the risk for
chronic osteomyelitis, chronic infection can occur and can be difficult to
treat. Organisms can survive in bone, and the accompanying bone necrosis may
limit antibiotic penetration into infected areas. Although acute hematogenous
osteomyelitis is typically treated with medical therapy alone, chronic disease
often requires both medical and surgical treatment. Aggressive surgical
techniques, which involve complete d
ébridement of necrotic bone as well as the creation of muscle flaps for
revascularization, are often required.
There remains no consensus on the duration of antibiotic therapy for chronic
osteomyelitis. If at all possible, medical therapy should be dictated by the
results of culture obtained at the time of surgery. Treatment courses of 3 to 6
months are reported to be generally effective.
Selected Readings
Kallio MJ, Unkila-Kallio L, Aalto K, et al. Serum C-reactive protein,
erythrocyte sedimentation rate and white blood cell count in septic arthritis
of children.
Pediatr Infect Dis J 1997;(16)4:411–413.
Karwowska A, Davies HD, Jadarji T. Epidemiology and outcome of osteomyelitis in
the era of sequential intravenous: oral therapy.
Pediatr Infect Dis J 1998;(17)11:1021–1026.
Kocher MS, Zurakowski D, Kasser JR. Differentiating between septic arthritis and
transient synovitis of the hip in children: an evidence-based clinical
prediction algorithm.
J Bone Joint Surg Am 1999;81(12):1662–1670.
Martinez-Aguilar G, Hammerman W, Mason E, et al. Clindamycin treatment of
invasive infections caused by community acquired, methicillin-resistant and
methicillin-susceptible
Staphylococcus aureus in children. Pediatr Infect Dis J 2003;22(7):593–599.
Moumile K, Merckx J, Glorion C, et al. Osteoarticular infections caused by Kingella kingae in children: contribution of polymerase chain reaction to the microbiologic
diagnosis.
Pediatr Infect Dis J 2003;22(9):837–839.
Newton PO, Ballock RT, Bradley JS. Oral antibiotic therapy of bacterial
arthritis.
Pediatr Infect Dis J 1999;(18)12:1102–1103.
Prober CG, Yeager AS. Use of the serum bactericidal titer to assess the adequacy
of oral antibiotic therapy in the treatment of acute hematogenous
osteomyelitis.
J Pediatr 1979;95(1):131–135.
Yagupsky P, Dagan R. Kingella kingae: an emerging cause of invasive infections
in children.
Clin Infect Dis 1997;24(5):860–866.
Pictures
Book Source Details
- Book Title: Pediatric Infectious Disease
- Author(s): Donald Janner MD
- Year of Publication: 2004
- Copyright Details: Pediatric Infectious Disease, Copyright © 2004 Lippincott Williams & Wilkins.
More About Psoriatic Arthritis
More Medical Textbooks Online about Psoriatic Arthritis
Review other book chapters online related to Psoriatic Arthritis:
Medical Books Excerpts
- Psoriasis
- "Professional Guide to Diseases (Eighth Edition)" (2005)
- [ read ]
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
|
|
More About This Book:
Title: Pediatric Infectious Disease
Authors: Donald Janner MD
Publisher: Lippincott Williams & Wilkins
Copyright: 2004
ISBN: 0-7817-5584-0
|
|
» Next page: Surveys relating to Psoriatic Arthritis
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
