Bone and Joint Infections

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Bone and Joint Infections
Janet Wong, M.D.

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Acute Osteomyelitis - Microbial Etiology
Neonate Infant Older Chid
Group B streptococcus
S. aureus
Candida sp.
Enterobacteriaceae
other streptococci
S. aureus
S. pyogenes
S. pneumoniae
H. influenzae
S. aureus
S. pyogenes
Salmonella (SSA)
There are three different routes of infection in children. The most
common seems to be the hematogenesis route, which gains
entry into the bone from the blood stream. Less commonly is by
direct inoculation and this can be a puncture wound, such as
stepping on a nail or something. This can also occur following
trauma or surgery. Finally, a particular spread, which is really
rare in children and seems to be more common in adults with
various disabilities, especially alterations in blood flow.

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Unusual Organisms and Osteomyelitis
. Penetrating trauma: soil organisms, yeast, gram negative
. Hemoglobinopathies: salmonella
. Brucella: sacroiliitis
. IV drug abuse: P. aeruginosa
. Chronic Osteomyelitis: Gram negative enteric, Staphylococcus
. Fractures, surgery: chronic osteomyelitis
. Contiguous Infection: anaerobes (bite, ulcer, sinusitis, mastoiditis)
. Fungi: disseminated H. capsulatum, C. immitis
What is thought to happen from the hematogenesis standpoint is
that the during a course of bacteremia, as the organisms enter
into the bone through the nutrient artery towards the growth
plate, there are these loose capillaries that are said to have
sluggish blood flow in them. It is also thought that maybe there is
a fully developed reticulum within this system. There does seem
to be evidence of low oxygen within the metaphysis, and we
always hear about this preceding history of trauma as a possibly
predisposing factor. Perhaps this is simply disruptive blood flow,
but the history of trauma to children is common, and it is hard to
know what really this is contributing to the pathogenesis.
The nutrient artery penetrates into the diaphysis of the bone,
moving up into the metaphysis and making a hairpin turn at the
epiphysis. This is why it is in a long individual, at least for the
tubular long bones, that osteomyelitis is more common at the
ends of the bones because of these here hairpin turns.
More recently there is some evidence in animals, specifically
chickens, who actually can develop osteomyelitis spontaneously.
A chicken strain of Staphylococcus aureus that appears at the
endothelium within the capillaries of bones have gaps, and it
looks as if the organisms can actually access the capillary system
to these particular gaps. If you take a Staph aureus and
inject it into the blood of the chicken, within 12 hours you can see
bacteria in some of these capillaries, and subsequently a day or
two later, evidence of infection at the metaphyseal epiphyseal
junction. So this is sort of an interesting animal experiment,
perhaps showing that these epithelial gaps, at least in chickens,
play some role.
Another factor in the development of osteomyelitis, at least
relating to Staphylococcus aureus, is the organism that produces
this sort of slimy stuff seems to make it more adherent to various
portions of the bones and thus more commonly associated with
osteomyelitis than those other organs.
Microbial etiology of osteomyelitis. In the neonate, the organisms
most commonly associated with osteomyelitis are typically
Group B streptococcus and Staphylococcus aureus. Very small
babies may involve for various gram negative bacteria and certainly
cause osteomyelitis as well as some other bacteria. In the
infant and older child, Staphylococcus aureus is the most common
cause. Streptococcus is the second most common.
Highly encapsulated organisms are unusual causes of
osteomyelitis, but 3 to 5% of patients with acute osteomyelitis
will have pneumococcus as the etiology.
In the older child, the same types of organisms are seen. Salmonella
is an important pathogen in patients with sickle cell anemia.
With penetrating injuries, organisms associated with the soil or
the skin or on clothes can of course lead to infection. Some of
these injuries, such as injuries associated with lawn mower
trauma, can grind the soil-type organism into the skin and ultimately
into the bone.
Now, sacroiliitis is not necessarily specifically an osteo, it is an
osteo-like illness we must keep in mind, especially in dealing
with certain populations, especially those who are likely to ingest
under pasteurized or nonpasteurized dairy products.
IV drug abuse is associated with P. aeruginosa, hopefully not a
major problem in kids, but it certainly is something that is seen in
adults.
Chronic osteomyelitis is associated with gram negative organ

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Clinical Manifestations of Osteomyelitis
..Fever, limitation of use of involved extremity or area.
. Localized swelling, warmth, erythema and pain (point tenderness)
. Pelvic osteomyelitis: hip and/or abdominal pain, difficulty walking, rectal
mass
. Vertebral osteomyelitis: back pain, tenderness over spinal processes
. Neonates-frequently accompanied by septic arthritis since epiphyseal,
metaphyseal junction within joint capsule; multiple bones Infected,
pseudoparalysis (high risk for sequelae
. Pseudomonas osteochondritis: foot puncture wound followed by local
findings in 48-96h; fever not prominent
isms. With fractures, this may lead to a chronic infection.
Contiguous infections which are not that common in pediatric
patients may be associated with anaerobic organisms. Perhaps
it is a decubitus ulcer, perhaps sinusitis, and after that may lead
to osteomyelitis of facial or scalp or skull bones.
Finally, certain fungi can disseminate and cause infection on the
bone.
The clinical manifestations of osteomyelitis include fever and
limitation of the extremity or the part of the body that is involved.
Localized swelling, warmth, erythema, and point tenderness
especially would be major clinical findings suggesting
osteomyelitis.
Now, outside of the extremities it could sometimes be very
difficult to pinpoint or even think about osteomyelitis. It could be a
subtle finding. For example, patients with pelvic osteomyelitis
may have a slight abdominal pain, perhaps they have some hip
pain or have some trouble walking, but when you examine their
extremities you really cannot pinpoint anything. It is not until you
do some more specific physical examinations, perhaps even a
rectal examination, that they sort of come up on this diagnosis.
Vertebral osteomyelitis typically occurs in older children with
back pain and tenderness when you palpate or stretch over the
spinal processes.
Finally, in neonates, one may see osteomyelitis in association
with septic arthritis because of the way the epiphyseal-
metaphyseal junction is actually positioned inside the joint, so
that the organism is able to rupture through the bone, it will
rupture into the joint space. In older children, typically if there is
a rupture through the periosteum; it will not rupture into the joint
space. Also, in contrast to what might happen in older children
where a single bone is what is most typically seen), in the neonate,
multiple bones are commonly infected.

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Differential Diagnosis of Osteomyelitis and
Septic Arthritis
. Rheumatic fever
. Cellulitis
. Skeletal Neoplasia (Ewing's sarcoma, leukemia)
. Bone Infarction in hemoglobinopathy
. Hemophilia
. Thrombophlebitis
. Child Abuse/Trauma
. Toxic synovitis
. Appendicitis, UTI, Psoas abscess (Pelvic osteomyelitis)

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Diagnosis of Osteomyelitis
. Laboratory
ESR or CRP elevated
Blood and bone aspirate cultures
. Radiology
Plain films - typical changes occur in 10-21 days (bone destruction,
periosteal new bone)
Tc99m Bone Scan - abnormal in over 90% (not as useful in neonates or
following fracture or surgery)
CT/MRI - may be helpful in unusual cases (pelvic, vertebral, skull)
Bone biopsy and culture - useful in unusual or chronic cases
Diagnosis of acute osteomyelitis. The erythrocyte sedimentation
rate is generally elevated. Other people like to get the C-reactive
protein and other nonspecific inflammatory laboratory tests. CRP
seems to come down more rapidly than the ESR. If there sed
rate is coming down slower, maybe I can draw out the therapy a
little bit longer.
From a radiographic standpoint, plain films are frequently helpful,
but generally they are useful later in the course because we
know they will not show specific changes for 7, 10 or 14 days.
This is how long it takes for decrease in bone mass to occur,
and that will show on your x-ray. Periosteal new bone formation
may also not be apparent for about 10 or 14 days.
The indications to undergo a technician bone scan. This is
abnormal in the vast majority of patients. It is not helpful in the
neonate, it is not helpful in those patients who have a fracture or
surgery. It is not helpful to patients with hemoglobinopathies
where an infarction and an infection cannot really be distinguished
by a typical bone scan.
In special situations, a CT and MRI could be particularly helpful.
This is especially true in patients that have pelvic osteomyelitis,
perhaps those with vertebral osteomyelitis. Then, many times
when it is not clear what is going on, you really would like to have
an organism, an actual bone biopsy as opposed to aspiration. A
biopsy where one can look at the bone under the microscope as
well as get a good culture can be very helpful.
I think these are most useful in the usual cases. The inflamed
bone is typically of osteomyelitis, for vertebral osteomyelitis they
are very helpful.
CT scans are very helpful. MRIs seems to be getting more
popular, and surgeons particularly like to obtain these types of
radiographic imaging prior to surgical approaches, so I think we
are going to see more MRI evaluations.

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Antibiotic Management of Osteomyelitis
Organism Agent Duration (minimum)
S aureus Nafcillin/oxacillin
Alternatives:
clindamycin or
cefazolin
3 weeks and ESR <2030
mm/h
Neonate - 4 weeks
Streptococci penicillin as above
P aeruginosa
osteochondritis
Ticarcillin/Piperacillin +
aminoglycoside
7-10 days if adequate
debridement
Salmonella ampicillin if susceptible;
cefotaxime,
ceftriaxone,
TMP-SMX
3-4 weeks
Antibiotic management of acute osteomyelitis. I think that for the
straight forward cases, related especially to Staph aureus, a
typically nafcillin or oxacillin is initially provided and that can be a
good initial therapy. Antibiotics should be continued either IV or
orally for a minimum of three weeks, and shows that treatment
for less than three weeks in acute osteomyelitis will lead to more
relapses. So, greater than three weeks is what is recommended,
and typically four to six weeks is what is provided. I like to see
the sed rate below 30 mL per hour before I discontinue therapy. I
think that whether you should provide therapy intravenously or
orally is somewhat up to each individual and the parents, and
what their home situation is like, what can be done from the
home IV therapy standpoint, and whether the organism has been
isolated.

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Management of Osteomyelitis
..Indications for Surgery
Drain purulent material from subperiosteal space or other tissue planes
Remove sequestra or infected foreign material
Débride and drain puncture associated infection
In neonate early drainage of bone and joint is critical
Chronic osteomyelitis
. Immobilize extremity
For Group A Streptococcus I think penicillin alone is fine.
Osteochondritis should be treated with a combination of antibiotics,
but an surgical debridement is most important.
For Salmonella, ampicillin is generally the treatment of choice if
the organism is susceptible to this antibiotic.
Serum titers, we are saying that we are taking a specimen of
blood at some point around the dose of an antibody before a
dose which would be the trough level or right after a dose IV,
perhaps an hour and a half after an oral dose would typically
represent the peak in the serum concentration and therefore test
the inhibition of the organism. You simply take the organism
which you hopefully have identified and have isolated in the
micro lab, and inoculate that into serial 2-fold solutions of this
serum.
As I mentioned, typically you like to treat these patients for four to
six weeks; either IV or orally depending on the organism and the
situations. Now, there are some times when you want to perform
surgical drainage; I think that if the surgeon went in to aspirate
the region or he might even see it on an MRI scan or CT scan,
there is an actual subperiosteal abscess that should be drained.
If there is a sequestra or there is swollen material within the
bones, that needs to be drained. In the neonate, these need to
be drained.

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Etiology of Septic Arthritis and Age
Organism Neonate 2-36 months >36 months
S. aureus +++ +++ +++
S ,pneumoniae + + ++
S. pyogenes + +
Group B streptococcus +++
N. gonorrhoeae + + (adolescent)
Candida sp. ++
H Influenzae
(unimmunized) + ++ +
Salmonella (SSA) ++ ++
Kingella kingae ++
Puncture wounds of the foot frequently are caused by nail injuries
through the tennis shoe or some other shoe penetration and
inoculation of the bones. The majority of the patients have Pseudomonas
aeruginosa isolated either by itself or combination of
Staph aureus or streptococci.
When the surgeons explored the wounds, osteochondritis was
noted in all of the patients. There was also some septic arthritis
and some cutaneous abscesses also noted. So, the course of
exploration clearly is important. I think it is a conclusion that in
this infection, which is a infection of cartilage, that it is important
to perform the optimum surgery which would be to débride and
devitalize the infected soft tissue cartilage and bone. You need to
drain these joints. Then when you do that, one may only have to
treat with antibiotics for perhaps seven to ten days. So, this is in
contrast to what we are typically taught in treating osteomyelitis
for a prolonged period.
Organisms that cause septic arthritis in children. Again, in the
neonate, Staph aureus and Group B streptococcus are going to
be the leading organisms. Candida albicans and gram negative
are also apparent in premature infants. In the child between 2
and 36 months of age, Staph aureus is the most common. The
second most common is going to be pneumococcus. Salmonella
is something to think about in patients with
hemoglobinopathies. In older individuals Staph aureus, Group A
strep, and pneumococcus are the leading causes of septic
arthritis.

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Clinical Manifestations of Septic Arthritis
..Acute onset fever, refusal to walk or limp
. Large joints (knee, hip, ankle) most common
. Swelling, warmth, erythema of joint with decreased mobility
. Abduction and external rotation is typical with hip
. In neonate systemic symptoms may be minimal
. In neonate multiple joints and contiguous osteomyelitis are common
. Small joints tend to be involved with gonococcal infection
Clinical manifestations of septic arthritis. We have the acute
onset of fever, refusal to walk, a limp would be the classic manifestation
in a baby. Perhaps the parents indicate that when they
change the diaper the baby is crying. Most of the time large joints
are involved. You might see a swelling, warmth, erythema, and
decreasing mobility in the joint. In the hip, the classic presentation
would be abduction and external rotation. In the neonate,
however, the symptoms may be very minimal. You might have
multiple joints involved and many bones infected as well, and it
is more or less hip. When you look at this baby you might see
that there is a slight dyssymmetry, and, in the baby, you may
illicit some pain on movement but it may be very subtle.

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Differential Diagnosis of Septic Arthritis
..Nonbacterial infection- virus, hepatitis, Tb, fungi, Lyme disease
. Juvenile rheumatoid arthritis, other collagen vascular disease
. Acute rheumatic fever
. Inflammatory bowel disease
. Leukemia
. Toxic synovitis, psoas abscess, pelvic osteomyelitis (when unable to bear
weight)
. Reactive arthritis (Shigella, Yersinia, Salmonella; Endocarditis
. Trauma (hemarthrosis)
. Cellulitis

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Evaluation- Septic Arthritis
1. Blood cultures positive in approximately 40% of cases
2. Synovial fluid - culture and Gram-stain
WBC count/mm3 %PMN Fluid: blood
glucose
Septic arthritis >50,000 90% 999 (30%)
JRA <15-20,000 60% normal to 9
(75%)
3. Vaginal or urethral culture if appropriate
4. Plane Radiograph: soft tissue swelling, joint space widening, osteomyelitis
5. Bone joint Tc-99m Scan
In the evaluation of septic arthritis, a blood culture is very helpful
and in some studies it has been positive in up to 40% of patients.,
what you want to get is a sample of the synovial fluid, a
blood culture, and a gram stain. Classically, if the white blood
cell count of the synovial fluid is greater than 50,000 with predominance
of polys, then this most likely a bacterial infection. If
the count is between 15,000 to 20,000, maybe less than 10,000,
with a smaller proportion of polys and the glucose limit is normal,
this is more likely to be a juvenile rheumatoid arthritis or
some other collagen vascular disease.
If we are dealing with an adolescent, and GC is a consideration,
then vaginal or urethral cultures should be obtained. Sometimes
the plain radiography can give you some additional clues as to
the foreign body scenario and a bone joint scan can sometimes
be useful as well.

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Empiric Antibiotics for Septic Arthritis
Age Agents Duration
Neonate Nafcillin/Vancomycin
+
aminoglycoside/
cefotaxime
3 weeks
Infant or child Nafcillin/oxacillin
add cefotaxime/
ceftriaxone
if no Hib vaccine
(cefuroxime)
3 weeks
S. aureus
2 weeks
H. Influenzae
Adolescent with presumed
GC
Ceftriaxone 7 days
Immunocompromised
child
Nafcillin/oxacillin plus
aminoglycoside
or
extended spectrum
cephalosporin
3 weeks
Empiric antibiotics for septic arthritis. Nafcillin is the drug that we
would use in the nursery now. Vancomycin might be started
initially because of what is going on in your nursery with the
aminoglycoside or cefotaxime. In the infant or child this should
read Nafcillin or oxacillin, plus cefotaxime regardless of Hib
immunization, because of the problem with penicillin is just a
pneumococcus. If one should have the organism then, I think you
can tailor the treatment more readily. In the adolescent,
ceftriaxone should be the drug.

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Septic Arthritis: Indications for Surgery
..Join remains swollen and erythematous after repeat needle aspiration
. Removal of foreign material secondary to penetrating
. Hips should be drained surgically
. In neonate surgical drainage of most joints indicated
. Arthroscopic lavage of knee alternative to arthrotomy
Indications for surgery. If you have repeat aspiration of the joint
and it remains swollen and erythematous, surgery of the joint is
indicated to remove foreign material, certainly all hips should be
drained. Some people might say all shoulder infections as well.
In some situations you can actually do arthroscopy rather than
surgical incision and drainage. It depends on the site and size of
the joint. There are some risk factors for outcome for septic
arthritis that I have also provided for you.

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Risk Factors for Sequelae of Septic Arthritis
..Young age <6-12 months (especially neonate)
. Prolonged duration of symptoms prior to treatment
. Hip and shoulder infection (especially with S. aureus
. Sequelae
Cartilage damage, stiff joint with poor mobility, abnormal bone growth if
epiphysis involved, unstable joint, chronic dislocation

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Discitis - Clinical Manifestations
..Low-grade fever
. Infants: Refusal to sit, pain when changing diaper
. Young child: Hip or leg complaints, and refusal to walk or limps; irritable
. Older child with back pain, abdominal pain
. Pain on palpation over vertebral processes
. Paraspinal muscle spasm
. Differential diagnosis: Toxic synovitis, vertebral osteomyelitis, epidural
abscess, pelvic osteomyelitis, sacroiliitis (Brucellosis)
Discitis or disc space infection. This is more common in young
children. The history can be one of nominal pain, a back pain, or
difficulty walking, and a child not wanting to sit. The diagnosis is
typically made on plain film and bone scans. If you do an MRI or
CT on a patient, it can look terrible. Management is with an oral
antistaphylococcal agents and let the child ambulate as tolerated,
usually in their own room with bed rest.

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Discitis- Diagnostic Evaluation and Management
..Plan radiographs: disc space narrowing
. Bone scan: abnormal uptake in disc space and adjacent vertebral bodies
. MRI or CT are necessary if clinical and initial radiographic findings are not
typical
. Management: Rest and oral antistaphylococcal antibiotic for 34 weeks and
ESR <20 mm/hr

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