1. Osteomyelitis

2. Epidemiology.
Osteomyelitis and suppurative arthritis are most common in young children
1/3 cases < 2 y/o
1/2 cases < 5 y/o
boys : girls, usually 2:1
1/3 cases have minor, closed trauma

3. Etiology.
A microbial etiology is confirmed in about 3/4 of cases of osteomyelitis
Staphylococcus aureus
the most common infecting organism in all age groups
Group B streptococcus and gram-negative enteric bacilli
prominent pathogens in neonates
group A streptococcus
less than 10% of all cases
After 6 yr of age, most are S. aureus

4. Etiology. Exclusive. other consideration:
puncture wounds of the foot: Pseudomonas aeruginosa
sickle cell anemia: Salmonella and S. aureus
other consideration:
penetrating injuries: atypical mycobacteria
Fungal infections usually occur as part of multisystem disseminated disease
Candida osteomyelitis sometimes occursin neonates with indwelling vascular catheters
Primary viral infections of bones--> rare;
but complain of arthralgia or arthritis may be due to immune responce

5. Pathogenesis In newborns and young infants:
transphyseal blood vessels connect the metaphysis and epiphysis
common for pus from the metaphysis  joint space
latter part of the first year of life, the physis forms
obliterating the transphyseal blood vessels
later childhood the periosteum becomes more adherent,
favoring pus to decompress through the periosteum
growth plate closes in late adolescence
begins in the diaphysis, and can spread to the entire intramedullary canal

7. Pathogenesis.
In the metaphysis, nutrient arteries branch into nonanastomosing capillaries under the physis, which make a sharp loop before entering venous sinusoids draining into the marrow
bacterial focus established --> phagocytes --> inflammatory exudates --> metaphyseal space--Halverson system and Volkmann canals) --> subperiosteal space --> impairing blood supply to the cortex and metaphysis

9. Clinical Manifestations.
signs and symptoms highly dependent on the age,
earliest signs and symptoms are often subtle
latent period of 10 to 12 days between the time of onset of clinical symptoms and the development of definite radiographic changes in bone.
Neonates:
pseudoparalysis
Half of do not have fever , may not appear ill

10. Clinical Manifestations.
Older infants and children
fever, pain, and localizing signs such as edema, erythema, and warmth
limp or refusal to walk
Local swelling and redness with osteomyelitis may mean that the infection has spread out of the metaphysis into the subperiosteal space, representing a secondary soft tissue inflammatory response

11. Clinical Manifestations.

12. Clinical Manifestations.
upper extremities account for one fourth of all cases. Flat bones are less commonly
Several bones or joints are infected in fewer than 10% of cases
exceptions are gonococcal infections and osteomyelitis in neonates
two or more bones are involved in almost half of the cases

13. Diagnosis. Take samples:
Aspiration of the infected site for Gram stain and culture
steel needle is needed to penetrate the cortex into the metaphysis.
If pus is encountered in the subperiosteal space, there is no need to go farther.
If gonococcus is suspected,
cervical, anal, and throat cultures should also be obtained
blood culture should be performed

14. Diagnosis. Other Lab. Exam
no specific laboratory tests for osteomyelitis
CBC/DC, ESR, CRP--> very sensitive but not specific
normal test results cannot r/o osteomyelitis
can monitor dz progress

15. Diagnosis. RADIOGRAPHIC EVALUATION. Plain Radiographs.
Within 72 hours of onset of symptoms of osteomyelitis
soft tissue technique, displacement or obliteration of the normal fat planes adjacent to deep muscle
compared to the opposite extremity,
can show displacement of the deep muscle

16. Diagnosis. Examination obtained 10 days after the onset
B: Repeat examination 1 week

17. Diagnosis. Plain Radiographs.
minimal amount of periosteal new-bone formation laid down parallel to the outer margin of the cortex
The actual disease process is usually much more extensive than showed by radiograph

18. Diagnosis. Examination 7 days after the onset
3 months later shows extensive new-bone formation

19. Diagnosis. Ultrasonography.
detecting joint effusion and fluid collection in the soft tissue and subperiosteal regions
may guide localization for aspiration or drainage.

20. Diagnosis. Computed Tomography and Magnetic Resonance Imaging.
CT is ideal for detecting gas in soft tissues
Increased attenuation occurs within the bone marrow early in the disease due to edema and pus

21. Diagnosis.
MRI is the best radiologic imaging technique for the identification of abscesses and for differentiation between bone and soft tissue infection
acute osteomyelitis, purulent debris and edema appear dark with decreased signal intensity on T1 weighted images opposite is seen in T2 weighted images
for possible surgical intervention
MRI is particularly useful in the evaluation of vertebral osteomyelitis and diskitis  clear delineation

23. Diagnosis.
MRI
MRI does not reliably distinguish osteomyelitis from noninfectious bone marrow edema
not sensitive to changes within the cortex

24. Diagnosis. Radionuclide Studies.
be valuable especially if multiple foci are suspected
Technetium-99 methylene diphosphonate (99m Tc), which accumulates in areas of increased bone turnover
99mTc 3 phase perfusion, blood pool, and delayed images
Any areas of increased blood flow or inflammation can cause increased uptake of 99m Tc in the
first phase (5–10?min) and
second phase (2–4?hr),
but osteomyelitis causes increased uptake of 99m Tc in the third phase (24?hr)

25. Diagnosis. Radionuclide Studies.
sensitivity (84–100%) and specificity (70–96%)
can detect osteomyelitis within 24–48?hr after onset of symptoms
Gallium-67 uptake, Indium-111 leukocytes is more specific for infection
sensitivity in neonates is much lower owing to poor bone mineralization

26. Treatment.
Optimal treatment of skeletal infections requires collaborative efforts of pediatricians, orthopedic surgeons, radiologists, and physiatrists
one should not wait for the development of radiographic evidence of disease before treatment
empirical antibiotic
antistaphylococcal penicillin, such as nafcillin or oxacillin, and a broad-spectrum cephalosporin, such as cefotaxime
aminoglycoside may be take place of cephalosporin
but reduced antibacterial activity in sites with decreased oxygen tension and low pH

27. Treatment In infants and children younger than 5 yr of age
Cefuroxime
After 5 yr of age and in the absence of special circumstances
nafcillin or cefazolin
With sickle cell disease , gram-negative enteric bacteria are common
broad-spectrum cephalosporin such as cefotaxime or ceftriaxone

28. Treatment
When the pathogen is identified, appropriate adjustments in antibiotics are made
If a pathogen is not identified and a patient's condition is not improving
re-aspiration or biopsy
Recheck diagnosis

29. Treatment Duration of antibiotic
(1) the patient shows prompt resolution of signs and symptoms (within 5–7 days) and
(2) the ESR has normalized; a total of 4–6 wk of therapy may be required
S. aureus or gram-negative bacillary infections, the minimum duration of antibiotics is 21 days
group A streptococcus, S. pneumoniae, or H. influenzae type b, antibiotics minimum of 10–14 days
Pseudomonas postoperative need total of 7 d treatment
Immunocompromised, mycobacterial or fungal infection patients generally require prolonged courses

30. Treatment
Oral route
Changing antibiotics from the intravenous route to oral administration when a patient's condition has stabilized, generally after 1 wk
serum bactericidal titers, or Schlichter titers, 45–60?min after a dose of suspension or 60–90?min after a capsule or tablet.
A serum bactericidal titer of 1:8 or more is considered desirable
ß-lactam drugs for staphylococcal or streptococcal infection, a dosage 2~3 times that used for other infections is prescribed

31. Treatment SURGICAL THERAPY.
When frank pus is obtained from subperiosteal or metaphyseal aspiration a surgical drainage procedure is usually indicated.
penetrating injury and when a retained foreign body
Infection of the hip is considered a surgical emergency
chronic osteomyelitis consists of surgical removal of sinus tracts and sequestrum Antibiotic therapy is continued for several months until clinical and radiographic

32. Prognosis.
Failure to improve or worsening by 72?hr requires review of the appropriateness of the antibiotic therapy
CRP typically normalizes within 7 days after start of treatment; ESR typically rises for 5–7 days, then falls slowly; dropping sharply after 10–14 d
Recurrence of disease and development of chronic infection after treatment < 10% of patients
initiation of medical and surgical therapy < 1 wk of onset of symptoms  better prognosis

33. SUBACUTE AND CHRONIC OSTEOMYELITIS
Bone Abscess
lucency area surrounded by an irregular zone of dense sclerosis.
The overlying cortex is usually thickened by periosteal new-bone formation

34. SUBACUTE AND CHRONIC OSTEOMYELITIS
Involucrum and Sequestrum Formation
Sequestra become avascular by losing their
periosteal supply: periosteum is stripped, elevated from cortex
intramedullary supply: infection causes vascular thrombosis
areas of dense bone surrounded by zones of lucency

35. SUBACUTE AND CHRONIC OSTEOMYELITIS
involucrum is a shell of bone formed by the periosteum that surrounds and encloaks a sequestrum
Involucrum and sequestrum formation in osteomyelitis  more common in children than in adults
MRI:
focus of active infection is similar to that of a bone abscess, low on T1, higher than marrow on T2, surrounded by a low-intensity rim on both

36. DIFFERENTIAL DIAGNOSIS.
trauma
Neuroblastoma
Primary bone tumors
Cellulitis
DVT

37. Cellulitis
skin infection, soft-tissue swelling is superficial and does not involve the deeper tissues adjacent to the bone.

38. Neuroblastoma
arises from sympathetic nervous tissue, often within the adrenal gland.
A palpable mass in the abdomen may be the first evidence
metastatic neuroblastoma is the most common malignant-appearing tumor before the age of 1 year in bone tumor
Calcification often is visible within the primary tumor

39. Neuroblastoma X-ray cranial sutures are spread
In the skull: Thin, whisker-like calcifications frequently extend out and inward
long tubular bones:
moth-eaten, and the cortex often eroded
Periosteal new-bone formation may parallel the cortex or form thin spiculations at right angles to the cortex
Ewing's tumor, neuroblastoma, and leukemia, may have a similar radiographic appearance, particularly in the long bones.

40. Neuroblastoma

41. Neuroblastoma

42. Ewing's tumor
malignant tumor arising in the red bone marrow and closely related histologically to reticulum cell sarcoma
Mostly: 5 ~ 25 y/o ; rarely after 30 y/o; male> female
long bones, extremities, femur, metaphysis
Exception: > 20 y/o, flat bones > long bones
Metastasize easy, multiple lesions may be present
symptoms : pain, swelling; often fever and leukocytosis, like osteomyelitis

43. Ewing's tumor (L) Laminated, onionskin, periosteal new-bone formation
(R) permeative destruction and a well-defined, laminated Codman's triangle

44. Ewing's tumor
X-ray
permeative, poorly marginated, destructive lesion that perforates the cortex
overlaid by a laminated, , onionskin periosteal reaction
Others may find: Codman's triangles, Fine spicules,
In the long bones, differentiation of Ewing's tumor and osteomyelitis may be difficult