This document discusses osteomyelitis, an infection of bone and bone marrow. It defines the different types (acute, subacute, chronic), describes the mechanisms of infection spread, common pathogens, and pathophysiology. Diagnosis involves clinical features, lab tests, and imaging modalities like radiography, CT, MRI, ultrasound and bone scanning. Radiographic findings at different stages and features of chronic osteomyelitis are also outlined.

1. Department of Radiodiagnosis and Imaging
ASCOMS, Jammu

2. -Infection of bone and marrow is known as osteomyelitis.
-Osteomyelitis is divided into:
Acute osteomyelitis
Subacute osteomyelitis
Chronic osteomyelitis
There are certain types of named osteomyelitis;
Brodie's abscess
Chronic multifocal osteomyelitis
Sclerosing osteomyelitis of Garré

3. - Three basic mechanisms
allow an infection to reach
the bone;
1. Haematogenous spread
2. Contigious source of
infection
3. Direct implantation

4. - Primary haematogenous osteomyelitis is characterized by an
acute infection of bone caused by seeding of bacteria within
the bone from a remote source
- Haematogenous osteomyelitis usually occurs during period of
growth and thus occur primarily in children. However, all ages
may be affected and cases are even found in old age.

5. Type of organisms
 Bacteria, viruses and fungi can all infect bone, soft
tissues and joints. The pattern of infection depends
not only on the microorganism but also on the route
of infection and the patient's resistance or immunity.
In general, bacterial infections are more destructive
and move rapidly.
 Fungi and atypical organisms and tend to produce
slow and chronic infections with an infiltrative
pattern that may mimic malignancy.
 Tuberculosis and brucellosis exhibit a variety of
patterns that range from aggressive to indolent and
reparative

6.  Pathogens causing haematogenous
musculoskeletal infection are
generally those associated with
primary bacteraemias. Of
these, Staphylococcus aureus is by
far the most important, with
Haemophilus influenzae (in the
unimmunized), Streptococcus
pneumoniae, the beta-haemolytic
streptococci and the aerobic Gram-
negative rods also playing a role.

7. Pathophysiology:
- Metaphysis of the long bones are highly vascularized zones.
 From the diaphysis the medullary arteries reach upto the
growth plate—the area of greatest activity and branch into
capillaries. The venous systems in this area drains towards
diaphysis

8.  Thus, the vessel in this
zone are arranged in the
form of loop (hair pin
arrangement) resulting in
―sluggish flow‖ of
blood, leading to bacterial
enlodgement and thus
haematogenous
osteomyelitis.

9. - The degree of involvement of bone varies in infants, children
and adults being related to vascular difference of bone at
these ages.
- In infants, vessels penetrate the epiphyseal plate. Metaphyseal
infection can thus pass to the epiphysis and then the joint.

10. - Acute pyogenic arthritis is therefore a relatively common
sequelae of osteomyelitis in infants.
- The periosteum in infants is very loosely attached to
underlying bone pus easily elevates the periosteum and so
can extend to the epiphyseal plate along the shaft.

11. - In childhood, between 2 and 16 years, the epiphyseal plate
blocks extension of the infection.
- The epiphysis and joints are thus less frequently affected.

12.  In adults, after epiphyseal plates are fused, metaphyseal
and epiphyseal vessels are again connected so that septic
arthritis can recess.
 Periosteum, however, is well bound down and articular
infections via metaphyseal route are less likely.

13.  The infection spreads laterally, into the subperiosteal
space or to the joints in which synovial reflections extend
to the metaphysis, such as shoulder, elbow and hip joints.

14. - The formation of pus in the bone deprives local cortex and
medulla of its blood supply.
- Dead bone is formed as a result is resorbed by granulation
tissue. However pieces of dead bone, especially if cortical
or surrounded by pus, are not resorbed and remain as
―sequestra‖

15.  As sequestra are
devitalised they remain
denser than surrounding
vital bone, which becomes
demineralised due to
hyperaemia and
immobilisation.

16.  Reparative new bone formation starts roughly 10 days
after the onset of infection and new bone is generally laid
down along the periosteum resulting in formation of
―involucrum‖.
 As periosteum is poorly attached in infants, involucrum
formation is greater and so is the resorption of dead bone
and healing.

17.  The hallmark of infection is that aggressive and
rapidly changing features (lysis, cortical breach
and fracture) are mixed with slower reactions
(sclerosis, heterotopic bone and periosteal
reaction).
 If an abscess cavity forms in bone and breaks
through to the soft tissues and skin the
discharging sinus is a pathognomonic sign of
infection. The hole in the bone develops a
sclerotic margin and is called a cloaca.

18. DIAGNOSIS
 Early diagnosis of acute osteomyelitis is critical because
prompt antibiotic therapy may prevent necrosis of bone.
 Osteomyelitis is primarily a clinical diagnosis, although the
clinical picture may be confusing.
 An inadequate or late diagnosis significantly diminishes
the cure rate and increases the degree of complications and
morbidity; for these reasons, imaging modalities are
essential to confirm the presumed clinical diagnosis and to
provide information regarding the exact site and extent of
the infectious process.

19. Clinical features :
- Haematogenous osteomyelitis usually presents with a
slow insidious progression of symptoms.
- Direct osteomyelitis generally is more localised, with
prominent signs and symptoms.

20. - General symptoms of osteomyelitis are :-
 Fever
 Fatigue
 Irritability
 Malaise
 Restriction of movement of limb
 Local edema, erythema and tenderness

21. Lab Findings:
- WBC counts are elevated with increased polymorphoneuclear
leukocyte count.
- C-relative proteins – level is elevated and is more useful than
ESR.
- ESR is usually elevate 90%.
- With osteomyelitis, culture or aspiration findings in samples of
infected site are important with over 25% cases pus being
sterile.
- Blood culture results are positive in 50% patients with
haematogenous osteomyelitis.

22. Radiological Findings
 The evaluation usually begins with plain radiographs
in all patients suspected of having osteomyelitis;
 plain radiographs may
suggest the correct diagnosis,
exclude other diagnostic possibilities, or
provide clues for underlying pathologic conditions.

23.  Radiography;
- The earliest radiographic signs of bone infection are soft
tissue swelling and loss of fascial planes. These are
usually encountered with in 24 to 48 hours of infection.

24.  Typical early bony changes include:
 lytic lesions,
 periosteal thickening
 endosteal scalloping,
 osteopenia,
 loss of trabecular architecture,
 and new bone apposition
- The destructive lytic lesion, usually occurs within 7 to 10 days .
- This is followed by elevation of periosteum and layered new
bone formation after 3 to 6 weeks.
- The dead bone (i.e. sequestrum formation) occurs at 3-8 weeks.
It appears dense as it does not participate in normal bone
mineral metabolism because of loss of its vascular supply.

25. - Osteopenia in the surrounding bone due to
hyperaemia, enhances the density of the sequestrum.
- With adequate treatment in infants and
children, remodelling reverts the appearance of bone to
normal with normal growth, unless the epiphyseal plate/
epiphysis have been damaged. However, in adults the
affected bone often remains sclerotic and irregular in
outline.

26.  Poorly defined osteolytic
area

28. Infection at the fracture site has delayed
union in the humerus. Note the extensive
periosteal reaction.

29.  Sequestra surrounded
by involucrum

31. Ultrasound
 Ultrasound (US) has multiple advantages: it is readily
accessible, can be performed quickly without delay
and with minimal discomfort to the patient, it is useful
in regions that are complicated by orthopedic
instrumentation and therefore might not be well seen
with MRI or CT, is useful in patients in whom MRI is
contraindicated, has a lower cost, does not use
ionizing radiation, and offers real time imaging.

32.  US can detect features of osteomyelitis several days
earlier than can conventional radiographs
(predominately in children).
 Acute osteomyelitis is recognized by elevation of the
periosteum by a hypoechoic layer of purulent material.
 Power Doppler sonography is useful to highlight
hyperemia around the periosteum and surrounding
soft tissue abscesses

34. Radionuclide scanning
- Where plain radiographs cannot show changes in
osteomyelitis before 10-14 days, bone scintigraphy shows
positive findings much earlier, usually within 3 days and
sometimes as early as 24-48 hours.
- Standard technique involves ―triple phase‖ bone scanning
using ―technetium 99 agents).

35. - The first phase shows blood flow, second phase is the
blood pool phase of the inflamed region and the third
phase which is the delayed skeletal scintigraphy phase
involves acquiring images after 2-4 hours and represents
uptake by bone.
- Osteomyelitis is hot on all phases.

36. A false positive result can occur in;
degenerative disease,
healing fracture
loose prosthesis
crystal arthropathies
Arthritis
Neoplasia
cellulites

37. CT scanning
 CT provides excellent multiplanar reconstructions of the
axial images allowing delineation of even the most subtle
osseous changes
 useful method to detect early osseous erosion and to
document the presence of sequestrum, foreign body, or gas
formation
 Though of less value in diagnosis, CT demonstrates changes in
subacute or chronic osteomyelitis well.
 Sequestra, as on conventional films is shown as area of dense or
high attenuation spicules of bone lying in areas of osteolysis.

38. - Cloacae, periostitis and local soft tissue masses are shown
and enhance on I.V. contrast administration.
- CT guided biopsy is used to obtain material for culture.

40. M.R.I. findings
 MRI is highly sensitive for detecting osteomyelitis as
early as 3 to 5 days after the onset of infection
 MRI demonstrated osteomyelitis as early as isotope
scanning and where available is the modality of choice
in diagnosis of musculoskeletal infections.
 commonly used sequences include T1, T2 and STIR .
 The combination of short-tau inversion-recovery (STIR)
and T1 spin echo sequences shows a high sensitivity and
specificity

41.  using appropriate sequences, changes in bone and soft
tissue oedema may be identified early, as well as ischemia
and destruction of cortex or marrow.
 Fatty marrow (medulla) is bright in signal on T1WI, while
compact cortex, having less fluid, has a low signal.
 Oedema and inflammation increase signal dramatically on
T2- weighted and especially on STIR.

42.  soft tissue extension of pus through cloacae and para-
osseous abscesses may be seen.
 Areas that become devitalized or necrotic shows loss of
signal and will not enhance after I.V. gadolinium.
 On MRI, a sequestrum is seen as a low signal intensity
structure on T1-weighted and STIR sequences, whereas
the surrounding granulation tissue is intermediate to low
signal intensity on T1-weighted images and high signal
intensity with STIR or T2-weighted sequences.

43.  With use of intravenous contrast (gadolinium), the
granulation tissue is enhanced, whereas the
sequestrum remains low
 Periosteal reaction and cortical bone are separated by
linear intermediate to high signal intensity on T2-
weighted or STIR images signal intensity
 Overall, MRI has been shown to be more sensitive and
specific than isotope bone scan in detection, localisation
and differentiation of osteomyelitis, cellulitis and abscess

46. Subacute osteomyelitis
 Those who have suffered from bone infection for
several days will start to exhibit bone reaction and
destruction.
 On plain radiographs a new periosteal reaction
with a fluffy margin is typical.
 US will show increasing soft tissue oedema and
subperiosteal fluid.
 MR is now probably the most sensitive technique
as the marrow changes predominate.
 CT and US have limited roles.

47.  On MR a
‘penumbra’
sign has been
described on T1
spin-echo
images. This
probably
represents a
layer of
granulation
tissue. It is
strongly
suggestive of
osteomyelitis

48. Chronic Osteomyelitis
- Chronic bone infections usually result from inadequately
treated acute osteomyelitis or from infections following
compound bone fractures.

49. Pathology
- Acute osteomyelitis commonly leads to chronic
osteomyelitis because of one of following reasons:
- Delayed or inadequate treatment—delay causes spread of
pus within the medullary cavity subperiosteally. This
results in destruction of cancellous bone leading to
formation of cavities and sequestra are responsible for
persistent infection.

50. - Type and virulence of organism – sometime despite early
adequate treatment of acute osteomyelitis the body defence
mechanism may not be able to control the damaging influence
of highly virulent organism and infection persists. Eg. H.
Influenzea, enterobacter and pseudomonas species.
- Reduced host resistance—malnutrition and underlying disease
conditions compromise the body’s defence mechanism, thus
letting the infection persist.


51. Disease states known to predispose patients to
osteomyelitis include
- Diabetes
- sickle cell disease,
- AIDS
- I.V.
- drug abuse,
- alcoholism,
- chronic steroid use,
- immunosuppression and
- chronic joint disease.

52.  When the infection persist because of the above reasons, the
host bone responds by generating more and more sub-
periosteal new bone formation.
 This results in thickening of the bone.
 The sub periosteal bone is deposited in a very irregular
fashion so that the osteomyelitis bone has an irregular
surface.
 The continuous discharge of pus results in the formation of a
sinus. With time, the wall of the sinus gets fibrosed and the
sinus becomes fixed to the bone.

53. Clinical Features in chronic
Osteomylitis
- Pain.
- Local swelling.
- Chronic discharging sinus.
- Thickened, irregular bone- which can be appreciated on
comparing the girth of the affected bone with that of bone
on normal side.
 Adjacent joint stiffness – which may be either, due to
excessive soft tissue scarring or because of associated
arthritis of the joint.

54. Radiological features
 Radiographs show
 Thickning and irregularities of cortex
 There are sclerotic and leucent areas admixed with
bony thickning and defomities . This appearance is
because of granulation tissue seen surrounding the
sequestrum.
 Involucrum and cloacae are also seen .

55. Thickening of cortex, reactive sclerosis, destruction of medullary
cavity, fistula

56. Radiographic signs of activity in chronic
osteomyelitis
 Change from previous radiographs
 Poorly defined areas of osteolysis
 Thin linear periostitis
 Sequestration

57. SINOGRAPHY
 Opacification of a sinus tract can produce important
information that influences the choice of therapy. In
this technique, a small flexible catheter is placed
within a cutaneous opening. Retrograde injection of
contrast material defines the course and extent of the
sinus tract and its possible communications with
neighboring structures. Sinography may be combined
with CT for better delineation of the sinus tracts.

59. Post op osteomyelitis

60. Ultasound
 In chronic osteomyelitis, US can also be used to assess
involvement of the adjacent soft tissues. Soft tissue
abscesses related to chronic osteomyelitis are
identified as hypoechoic or anechoic fluid
collections, which may extend around the bony
contours

61. CT
 In chronic osteomyelitis, CT demonstrates abnormal
thickening of the affected cortical bone, with sclerotic
changes, encroachment of the medullary cavity, and
chronic draining sinus.
 Although CT may show these changes earlier than do
plain radiographs, CT is less desirable than MRI
because of decreased soft tissue contrast as well as
exposure to ionizing radiation.

62.  The major role of CT in osteomyelitis is the detection
of sequestra in cases of chronic osteomyelitis, as these
pieces of necrotic bone can be masked by the
surrounding osseous abnormalities on conventional
radiography.
 The presence of pieces of sequestered bone suggests
activity of the infectious process, and their detection is
helpful to guide the therapeutic options.
 CT is superior toMRI for the detection of
sequestra, cloacas, involucra, or intraosseous gas and
can help in the guidance of needle biopsies and joint
aspiration

64. MRI
 MR has been advocated as the imaging modality to
distinguish regions of active infection from fibrotic
regions representing scars from previous infection .
 Active foci of infection tend to have low to
intermediate signal on T 1WI and high signal intensity
on T2WI which is in marked contrast to the low signal
of thickened surrounding bone.

66. Named types of Osteomyelitis
 Brodie's abscess
 Chronic multifocal osteomyelitis
 Sclerosing osteomyelitis of Garré

67. Brodie's abscess
 Described by Brodie in 1832.
 This is a description given to an intraosseous abscess that is
surrounded by intense sclerosis . It is probably one type of
subacute infection.
 Brodie’s abscesses are especially common in children, more typically
boys. In this age group, they appear in the metaphyses, particularly
that of the distal or proximal portions of the tibia.
 As a rule sequestra are absent and a radioleucent tract may be
seen extending from the lesion into the growth plate(tunneling).
 The plain radiographs may mimic osteoid osteoma but cross-
sectional imaging will demonstrate a substantial cavity and biopsy
will reveal infection

69. Brodie's abcess tracking
into the growth plate

70. Chronic multifocal osteomyelitis
 In the 1970s it was noted that a number of children
presented with a low-grade form of bone disease that
behaved clinically like an acute osteomyelitis.
 Typically it affected the long bones and went on to a
sclerotic reaction. The first episode would settle and
some months or even a few years later there would be
recurrence at another site.
 No organisms are grown and the course of the disease
becomes chronic and relapsing.

71.  The clinical importance is to avoid repeated
biopsy once the relapsing nature of the condition
has been recognized.
 Plain radiographs are essential to recognize the
bone infection.
 Skeletal scintigraphy is a good method of
screening for other lesions
 whilst MRI is the best means of judging extent
and activity

72. Sclerosing osteomyelitis of Garré
 A rare type of osteomyelitis occuring in children and
young adults presenting with insidious onset of
pain, pyrexia and swelling.
 Symptoms recur at intervals for several years and
subside graudlly . .
 Radiological appearance is of intense sclerosis
resulting in thickned bone.
 There is predilection for involvement of mandible and
shaft of long bones.

73.  There is no discharging sinus
 No necrosis
 No purulent exudate
 Little granulation tissue

75. Non Pyogenic bone infections
 Tuberculosis
 Fungi
 Syphilis

76. Tuberculosis
 Tuberculous bone infection occurs secondarily
as a resolt of hematogenous spread from a
primary source such as lung or genitourinary
tract.
 Bone infection is most typically slow growing and
indolent. Tuberculous ‘caries’ is seen where the
margin of the bone is scalloped and eaten away.
Large ‘cold’ abscesses occur. This means that the
patient is surprisingly well given the size of the
collection

77.  Little or no surrounding reactive bone with presence of
osteopenia
 Affects epiphysis, metaphysis and diaphysis.
 Eccentric area of osteolysis is seen in metaphysic
 Transepiphyseal spread of lytic lesion
 No sequestrum formation is seen.
 Occasionally, destruction in the mid diaphysis of a
short tubular bone of the hand or foot(tuberculous
dactylitis) may produce a fusiform enlargement of the
entire diaphysis is called as spina vetosa.

78.  Lytic lesion with soft tissue
swelling
 No sclerosis or periosteal
new bone formation

80. Fungi
 A variety of fungi may affect bones and joints[59].
In general the infections tend to be slowly
developing and difficult to eradicate; they may
mimic tumours. There is an increased incidence
in areas of the world where the organisms
naturally reside.
 Fungal infections in the musculoskeletal system
are seen more often in immunosuppressed
patients. Fungi should be considered when the
bacteriological findings do not fit the clinical
presentation.

81. Destructive lesion , minimal sclerosis and no periosteal reaction

82. coccidiodomycosis

83. Syphilis
 Skeletal presentations are varied and mimic many
other diseases
 Congenital syphilis may cause a symmetric
periostitis with lamination. Granulomas
occurring in the metaphyses of long bones
produce lytic areas known as Wimberger's sign
 The growth plate may be abnormal with lytic
bands in the adjacent bone

85. Complications AND Sequale
 Growth disturbance (vicinity of growth plate)
 Pathological fractures
 Sinus tract neoplasm

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