RADIOLOGICAL
EXAMINATION OF THE
SKELETAL SYSTEM
DEPARTMENT OF ONCOLOGY AND
RADIOLOGY
PREPARED BY I.M.LESKIV
• The skeletal system provides structural
support and protection to the human body
and its internal organs, serves as primary
home for blood-forming tissues, and
stores several vital minerals, above all,
calcium. This lecture focuses on
alterations of the bony (structural
support) part of the skeletal system.
METODS OF EXAMINATION
Radiographic examination (X-Ray) is the key to the diagnosis of many
skeletal abnormalities. It is essential that each bone be examined in its
entirety, including the cortex, medullary canal (cancellous bone or
spongiosa), and articular ends. The position and alignment of joints are
determined. In children, the epiphysis and epiphyseal line or physis must be
observed. The adjacent soft tissues are examined. Obliteration of normal
soft-tissue lines and the presence of a joint effusion are of particular
importance. When disease is present, it is important to determine whether
the process is limited to a single bone or joint or whether multiple bones or
joints are involved. The distribution of disease is also a consideration. The
presence and type of bone destruction and bone production, the appearance
of the edges or borders of the lesion, and the presence or absence of cortical
expansion and periosteal reaction are also noted. The radiographic findings
are then correlated with the clinical history and the age and sex of the
patient to arrive at a logical diagnosis. The diagnosis may be firm in some
instances; in other cases, a differential diagnosis is offered since the exact
diagnosis ;cannot be determined.
METODS OF EXAMINATION
• COMPUTED TOMOGRAPHY (PLAIN FILM RADIOGRAPHY,
FLUOROSKOPY): Computed tomography (CT) is advantageous in the
evaluation of the skeletal system. It allows visualization of adjacent soft-tissue
structures and also the marrow in the medullary cavity. The position of
surrounding vascular structures can be determined by the use of contrast
media. CT has the added advantage of being more sensitive to the detection of
bone destruction than plain film radiography or standard tomography. CT
images are displayed in the axial or horizontal plane, and even sagittal and
coronal planes, with image reconstruction. Unfortunately, image reconstruction
degrades the image. Images are displayed with both bone and soft-tissue
windows. The soft-tissue window setting allows visualization of surrounding
soft tissue but is suboptimal for the bony skeleton. The bone window setting
maximizes the visualization of cortical and medullary bone .
METODS OF EXAMINATION
• MAGNETIC RESONANCE IMAGING: Magnetic resonance (MR)
imaging is of great value in the evaluation of the skeletal system, particularly
in the detection and evaluation of tumors, infection, bone infarction, and
ischemic necrosis. Because the image is dependent on the presence of
hydrogen, which is abundant in marrow fat, MR imaging visualizes the bone
marrow exquisitely. However, the hydrogen content of cortical bone is very
low, and MR imaging therefore is not as sensitive as CT for the evaluation of
cortical bone. MR imaging has the added advantage of displaying the
anatomy in any plane, including the coronal and sagittal planes, which are
distinctly advantageous in the demonstration or visualization of
abnormalities within bone and their relationship to surrounding soft tissue.
Discrimination between and differentiation of various soft tissues and
pathologic processes may be enhanced by varying the technical parameters
used for the examination. Full the armore, vascular structures are
demonstrated and are clearly visualized without the necessity of contrast
media injection.
METODS OF EXAMINATION
• SKELETAL SCINTIGRAPHY:
Skeletal scintigraphy or bone
scanning is a valuable adjunct to standard film radiography. Bone-seeking
radionuclides are taken up in areas of increased bone turnover. This occurs
normally at the growth plate in children and at abnormal sites in tumors,
infections, and fractures; in sites of reactive bone formation in arthritis; and
in periostitis regardless of the etiology. Technetium-99m-labeled
polyphosphates are the most common radiopharmaceuticals used,
particularly technetium-99m methyldiphosphonate ("mTc-MDP). Fifteen to
20 millicuries (mCi) is injected intravenously, and a scan is obtained two
hours later. The radiation-absorbed dose is very low, since the total body
dose is 0.009 rad/mCi. The agent is excreted in the kidneys and collects in the
bladder. The target organ—that is, the organ receiving the highest dose— is
the wall of the bladder, exposed to approximately 0.275 rad/mCi. Bone
scanning is more sensitive to areas of bone turnover and destruction than
plain film radiography or tomography. The bone scan may be positive in the
presence of a normal radiograph, well before the radiograph becomes
abnormal. However, the bone scan is less specific than the radiograph. Areas
of increased activity are detected, but the cause of the increase often cannot
be stated with certainty, and correlation with plain film radiographs or
computed tomography and magnetic resonance imaging is necessary to
establish a correct diagnosis.
SKELETAL GROWTH AND MATURATION
• OSSIFICATION OF THE SKELETON
• The process of bone formation in cartilage is known as endochondral
ossification, which causes bones to grow in length. Some bones are formed in
membrane, known as membranous bone formation. The bones of the cranial
vault are the principal example. Ossification occurs in both cartilage and
membrane in the mandible and clavicle. The tubular bones grow in their
transverse diameters by bone formation within the osteogenic cells of the
inner layer of the periosteum. This could be considered a form of
membranous bone formation.
• At birth, the shafts of the long tubular bones are ossified, but both ends
(epiphyses), with a few exceptions, consist of masses of cartilage. Cartilage is
relatively radiolucent as compared with bone, having the same density as soft
tissue on a conventional radiograph. Thus, at birth the ends of the bones are
separated by radiolucent spaces representing the cartilaginous epiphyses. At
variable times after birth, one or more ossification centers appear in the
epiphyses (the epiphyseal ossification centers). Exceptions occur at the distal
femur and proximal tibia epiphyses, where ossification centers appear during
the last 1 or 2 months of intrauterine life. The short tubular bones are similar
to the long bones except that they have an epiphysis at only one end.
SKELETAL GROWTH AND MATURATION
• The distal femur and proximal tibia epiphyseal ossification centers can be
used as indicators of fetal maturity. Formerly, radiographs of the mother's
abdomen were obtained to visualize these centers as evidence of fetal maturity
during the last month of gestation prior to induced labor or cesarean section.
Fetal maturity is now determined by ultrasonographic examination, which is
highly advantageous. Because it does not use ionizing radiation, it can be
employed throughout pregnancy and is safe, accurate, and free of side effects.
The times of appearance of the various epiphyseal ossification centers are
good indicators of skeletal age during infancy and early childhood.
• The flared end of bone is known as the metaphysis, and the tubular
midportion of the shaft the diaphysis. Between the metaphysis and epiphysis
lies the physis or cartilaginous growth plate consisting of four distinct zones—
the resting zone, the proliferating zone, the hypertrophic zone, and the zone of
provisional calcification. In the zone of provisional calcification, mineral salts
are temporarily deposited around the degenerating cartilage cells. Blood
vessels subsequently grow into the lacunae left by the degenerated cartilage
cells, bringing with them osteoblasts, specialized connective tissue cells whose
main function is the production of osteoid. Osteoid is the organic matrix in
which mineral salts are deposited to make bone. Osteoid is relatively
radiolucent and, when present in large amounts, will cause bone to appear
more radiolucent than normal. As osteoid is formed, the zone of provisional
calcification is replaced by trabecular bone.
• It is rather common to see one or more thin opaque lines crossing the shaft
near its ends. These are commonly known as "growth lines" and, while there
may be other causes for them, it is probable that in most cases they indicate a
temporary cessation of orderly ossification brought about by one or more
episodes of systemic illness.
SKELETAL GROWTH AND MATURATION
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Epiphysis: The cartilaginous end of a bone.
Physis: The cartilaginous zone between the epiphysis and
the calcified cartilage, also known as the growth plate or
the epiphyseal plate. When it becomes thin, in late
adolescence, it is sometimes called the epiphyseal line.
Metaphysis: The flared end of the shaft of a tubular
bone.
Diaphysis: The tubular shaft of a long bone.
Epiphyseal ossification center: The ossified portion of an
epiphysis.
Zone of provisional calcification: The zone of deposition
of mineral salts at the end of the shaft that serves as a
framework for the deposition of osteoid. It is seen in
roentgenograms as a thin white line or narrow zone.
Osteoid: The organic matrix that is formed by the
osteoblasts and that, when mineralized, becomes bone.
Endochondral ossification: The process by which bone is
formed from cartilage.
Intramembranous ossification: The process by which
bone is formed from membrane without a cartilaginous
stage; periosteal and endosteal growth are included.
Apophysis: An accessory ossification center that forms a
protrusion from the end or near the end of the shaft of a
long bone. Apophyses function as growth centers at
nonarticular margins of bone, i.e., the greater trochanter
of the femur or ischial tuberosity of the pelvis. They
serve as attachments for muscles or ligaments and do not
contribute to the length of a long bone.
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Normal long bones in (a) child and
(b) adult. Increase in length takes
place at the cartilagenous
epiphyseal plate. In the growing
child, calcification of cartilage
occurs at the interface between the
radiolucent growing cartilage and
the bone to give the zone of
provisional calcification, which is
seen as a dense white line forming
the ends of the shaft and
surrounding the bony epiphyses.
This calcified cartilage becomes
converted to bone. (If there is
temporary cessation of growth
then the zone of provisional
calcification may persist as a thin
white line, known as a 'growth
line', extending across the shaft of
the bone.) As the child grows older
the epiphyseal plate becomes
thinner until, eventually, there is
bony fusion of the epiphysis with
the shaft.
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b
• The radiological responses of bone to
pathological process are limited; thus similar xray signs occur in widely different conditions. It
should be noted that it takes time for the various
signs to develop; for example, in adults, it takes
several weeks for a periosteal reaction to be
visible after trauma and, in a child with
osteomyelitis, the clinical features are present
from seven to ten days before the first sign is
visible on the radiograph. In general, the signs
take longer to develop in adults than they do in
children. The signs of bone disease are :
- Decrease in bone density which may be focal or generalized.
Focal reduction in density is usually referred to as a lytic
area' or an area of 'bone destruction'. When generalized,
decrease in bone density is best referred to as 'osteopenia'
until a specific diagnosis such as osteomalacia or
osteoporosis can be made.
- Increase in bone density (sclerosis) which may also be focal
or generalized.
- Periosteal reaction. The periosteum is not normally visible
on a radiograph. The term 'periosteal reaction' refers to
excess bone produced by the periosteum, which occurs in
response to such conditions as neoplasm, inflammation or
trauma. Several patterns of periosteal reaction do not
correlate with specific diagnoses. At the edge of a very
active periosteal reaction there may be acuff of new bone
known as a Codman's triangle. Although often seen in
highly malignant primary bone tumours, e.g. osteosarcoma,
a Codman's triangle is also found in other aggressive
conditions.
Different types of periosteal
reactions, (a) Smooth
lamellar periosteal reaction
on the radius and ulna in a
case of non-accidental
injury, (b) Spiculated
(sunray) periosteal reaction
in a case of osteogenic
sarcoma (arrows), (c) Onion
skin periosteal reaction in a
case of Ewing's sarcoma
(arrows). Here the periosteal
new bone consists of several
distinct layers, (d) Codman's
triangle in a case of
osteogenic sarcoma. At the
edge of the lesion the
periosteal new bone is lifted
up to form a cuff (arrow).
b
a
c
d
• Cortical thickening also involves the laying down of new
bone by the periosteum , but here the process is very
slow. The result is that the new bone, although it may
be thick and irregular, shows the same homogeneous
density as does the normal cortex. There are no
separate lines or spicules of calcification as seen in a
periosteal reaction. The causes are many, including
chronic osteomyelitis, healed trauma, response to
chronic stress or benign neoplasm. The feature common
to all these conditions is that the process is either very
slowly progressive or has healed.
• Cortical thickening.
Note the thickened
cortex in the midshaft
of the tibia from old,
healed osteomyelitis.
• Alteration in trabecular pattern is a complex response
usually involving a reduction in the number of
trabeculae with an alteration in the remaining
trabeculae, e.g. in osteoporosis and Paget's disease. In
osteoporosis the cortex is thin and the trabeculae that
remain are more prominent than usual, whereas in
Paget's disease the trabeculae are thickened and
trabeculation is seen in the normal compact bone of the
cortex.
• Alteration in the shape of a bone is another complex
response with many causes. Many cases are congenital
in origin; some are acquired, e.g. acromegaly and
expanding bone tumours.
• Alteration in bone age. The time of appearance of the
various epiphyseal centres and their time of fusion
depend on the age of the child.
• Alteration of trabecular pattern in
Paget's disease involving the upper
part of the tibia leaving the lowest
part of the tibia and the fibula
unaffected. Note the coarse
trabeculae. The other features of
Paget's disease - thickened cortex
and bone expansion - are also
present.
Cortical thickening. Note the thickened
cortex in the midshaft of the tibia from
old, healed osteomyelitis.
Bone Trauma.
Imaging techniques.
Plain bone radiographs
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Plain radiography in bone trauma is invaluable in
order to:
diagnose the presence of a fracture or
dislocation;
determine whether the underlying bone is
normal or
whether the fracture has occurred through
abnormal bone (pathological fracture);
show the position of bone ends before and after
treatment of a fracture;
assess healing and complications of fractures.
Fracture Terminology
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Frequently, a fracture is very obvious but in some cases the
changes are more subtle. Fractures may be recognized or
suspected by the following signs:
Fracture line. The fracture usually appears as a lucent line. This
may be very thin and easily overlooked. Occasionally, the fracture
appears as a dense line from overlap of the fragments.
A step in the cortex may be the only evidence of a fracture.
Interruption of bony trabeculae is of use in impacted fractures
where there is no visible lucent line. This is, however,
a difficult sign to evaluate.
Bulging or buckling of the cortex is a particularly important
sign in children, where fractures are frequently of the green-stick
type.
Soft tissue swelling may be a valuable guide to the presence of an
underlying fracture.
A joint effusion may become visible following trauma. In
the elbow, where an effusion often indicates a fracture, fat pads
lie adjacent to the joint capsule and, if there is an effusion, they
will be displaced away from the shaft of the humerus on the
lateral view.
Fracture of the ulna appearing as
a sclerotic line (arrow).
• Fracture of forearm showing the value of
two views. (a) The fractures of the radius
and ulna show little displacement on the
frontal projection, (b) The lateral view,
however, shows a marked angulation.
Dislocation
• The joint surfaces no longer maintain their normal relationship to each
other. An associated fracture should be carefully looked for.
Fracture of neck of humerus
appearing as a step in the cortex
(arrow).
Colles' fracture showing the bony
trabeculae are interrupted across the
fracture site (arrow). There is also a
step in the cortex.
Greenstick fracture of lower end of radius in a
child. There is buckling of the cortex (arrows).
SPECIFIC INJURIES
Stress fracture
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Stress fractures are due to repeated, often minor,
trauma. They occur in athletes, particularly in the
tibia and fibula. Another example is the so-called
march fracture occurring in the shafts of the
metatarsals. Initially, despite the presence of pain,
a radiograph will show no evidence of a fracture
but if a further film is taken after 10-14 days a
periosteal reaction may draw attention to the
fracture site, where a thin crack may be visible. A
stress fracture may appear as a sclerotic band
across the bone and a fracture line may not
necessarily be visible. Radionuclide bone
scanning can be helpful in distinguishing stress
fractures from other causes of pain, because a
stress fracture will appear as an area of increased
uptake before any changes are visible on the
radiographs.
Insufficiency fracture
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An insufficiency fracture results from normal
activity or minimal trauma in weakened bone
commonly from osteoporosis or osteomalacia.
Compression fractures of the vertebral bodies are
the commonest insufficiency fractures but they
also characteristically occur in the sacrum, pubic
rami and femoral necks though other bones may
be involved.
a
b
Stress fracture, (a) Fracture appearing
as a sclerotic band (vertical arrows)
Stress fracture.
across the tibia accompanied by a
This film was taken periosteal reaction (horizontal arrow),
two weeks after the (b) In this calcaneum there is a
sclerosis adjacent to the fracture
onset of pain. It
shows a periosteal (arrow).
reaction (arrow)
around the
metatarsal shaft
although a fracture
cannot be seen.
Stress fracture. Radionuclide
bone scan showing increased
uptake in the tibia (arrow) of
this athlete with pain in the leg.
The radiographs at the time of
the scan were normal.
SPECIFIC INJURIES
Pathological fracture
• A pathological fracture is one that occurs through abnormal
bone. Pathological fractures may be the presenting feature of
both primary and secondary bone tumours. Often, the
causative lesion is obvious. Sometimes, particularly in ribs,
metastases responsible for fractures are ill defined and
difficult to see. In such cases the diagnosis rests on
recognizing the irregularity of the margins of the fracture. If
there is doubt about the diagnosis it is helpful to look
elsewhere in the skeleton for other metastases.
• Transverse fractures occur through abnormal bone,
particularly in Paget's disease. In these instances the Paget's
disease is always obvious.
Pathological fracture
Paget's disease showing incomplete fractures,
Pathological fracture of the
known as infractions, of the lateral aspect of the
humerus. There are widespread femur. Note the marked thickening of the cortex
lytic metastases from a carcinoma and bowing of the femur.
of the breast
BONE DISEASE
When considering the diagnosis and differential
diagnosis of bone diseases, it is convenient to
divide disorders into those that:
• cause solitary lytic or sclerotic lesions;
• produce multiple focal lesions, i.e. several
discrete lytic
or sclerotic lesions in one or more bones;
• cause generalized lesions where all the bones
show
diffuse increase or decrease in bone density;
• alter the trabecular pattern;
• change the shape of the bone.
BONE DISEASE
Solitary areas of lysis, sclerosis or a combination of the two, are usually one of the
following:
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bone tumours
a) malignant (primary or secondary)
b) benign
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osteomyelitis
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bone cysts, fibrous dysplasia or other non-neoplastic defects of bone
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conditions of uncertain nature such as Langerhans histiocytosis and osteoid osteoma.
`Primary malignant bone tumours and osteomyelitis are usually accompanied by periosteal
reaction. Pathological fractures may be seen through benign and malignant bone
tumours and through bone cysts.
The radiological diagnosis of a localized bone lesion can be a problem. Some conditions are
readily diagnosed but, in others, even establishing which broad category of disease is
present can be difficult. The initial radiological decision is usually to try and decide
whether the lesion is benign, i.e. stable or very slow growing, or whether it is
aggressive, i.e. a malignant tumour or an infection. It is also important to know the age
of the patient, since certain lesions tend to occur in a specific age range.
The precise diagnosis of a bone tumour can be notoriously difficult both for the radiologist
and the pathologist. Accurate histological diagnosis is essential for all malignant lesions
and it is important to realize that separate portions of a tumour may show different
histological appearances. In general, plain film radiography is the best imaging
technique for making a diagnosis, whereas CT and/or MRI often show the full extent of
a tumours to advantage. The main role for radionuclide bone scanning is to diagnose
metastatic bone disease. Metastatic malignant tumours are by far the commonest bone
neoplasm, outnumbering many times primary malignant tumours.
BENIGN TUMOURS
• Included under this heading are benign tumours such as enchondroma, certain
benign conditions similar to tumours, such as fibrous dysplasia and some
abnormalities which are difficult to classify, such as osteoid osteoma and
Langerhans histiocytosis. Some of these lesions are discussed below. In general,
benign lesions have an edge which is well demarcated from the normal bone by a
sclerotic rim. They cause expansion but rarely breach the cortex. There is no soft
tissue mass and a periosteal reaction is unusual unless there has been a fracture
through the lesion. Radionuclide scans in benign tumours usually show little or no
increase in activity, provided no fracture has occurred. CT and MRI scanning are
rarely needed in the evaluation of benign tumours.
• Enchondromas are seen as lytic expanding lesions most commonly in the bones of
the hand . They often contain a few flecks of calcium.
• Fibrous cortical defects (non-ossifying fibromas) are common chance findings in
children and young adults. They produce well-defined lucent areas in the cortex of
long bones . Fibrous dysplasia may affect one or several bones. It occurs most
commonly in the long bones and ribs as a lucent area with a well-defined edge and
may expand the bone. There may be a sclerotic rim around the lesion.
• A simple bone cyst has a wall of fibrous tissue and is filled with fluid. It occurs in
children and young adults, most commonly in the humerus and femur. Bone cysts
form a lucency across the width of the shaft of the bone, with a well-defined edge.
The cortex may be thin and the bone expanded. Often, the first clinical feature is a
pathological fracture.
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BENIGN TUMOURS
• Aneurysmal bone cysts are not true neoplasms, but they probably form
secondarily to an underlying primary tumour. Mostly they are seen in children and
young adults in the spine, long bones or pelvis. These lesions are purely lytic and
cause massive expansion of the cortex, hence the name 'aneurysmal'. They may
grow quickly and appear very aggressive but are nevertheless benign lesions. CT
and MRI may show the blood pools within the cyst. The major differential
diagnosis is from giant-cell tumour.
• An osteoid osteoma is a painful condition found most commonly in the femur and
tibia in young adults. It has a characteristic radiological appearance: a small
lucency, sometimes with central specks of calcification, known as a nidus,
surrounded by dense sclerotic rim. A periosteal reaction may also be present . CT
shows these features to advantage and osteoid osteomas can also be shown by
MRI. An important imaging investigation is radionuclide bone scanning which
shows marked focal increased activity. Radionuclide bone scanning is particularly
useful when the osteoid osteoma is difficult to see on plain film.
• Eosinphil granuloma is the mildest and most frequent form of Langerhans
histiocytosis (previously referred to as histiocytosis X). It occurs in children and
young adults and produces lytic lesions which may be single or multiple, most
frequently in the skull, pelvis, femur and ribs. Extensive lesions may be seen
giving rise to the so-called 'geographic skull'. Long bone lesions show bone
destruction which may be well defined or ill defined and may have a sclerotic rim.
A periosteal reaction is sometimes seen
A cylindrical cuff of bony cortex has been eroded by •
pressure from within, although you observe the thinning
best where you see cortex in tangent medially and laterally.
Across the thinned segment of bone at the level of the
arrows a jagged fracture has occurred and is seen on the
lateral surface as a distinct interruption of the cortex
Bone cyst. There is an expanding
lesion crossed by strands of bone in
the upper end of the humerus in a
child. The lesion extends to but does
not cross the epiphyseal plate.
Enchondroma
• Enchondroma (EC) is a benign intraosseous tumor of welldifferentiated cartilage occurring primarily in adults and
adolescents. It most frequently affects small tubular bones of
the hands and feet but can develop anywhere in the skeleton.
The monoclonality of chondrocytes in EC suggests a benign
neoplasm. EC may occur in multiplicity (enchondromatosis,
Oilier disease). Rarely, EC transforms to secondary
chondrosarcoma (CS). EC is usually asymptomatic except for
certain "obscure" pain sensations. Incidental radiographs show
well-defined radiolucent lesions with slightly pronounced
bony margins and sometimes calcification. Microscopy reveals
a somewhat disorganized, well-differentiated cartilage with
stippled calcification. Larger lesions may undergo
pseudocystic degeneration. The prognosis for small benign
ECs is good, and lesions may be followed without
intervention. Surgical intervention is suggested for mechanical
reasons or when suspicion of malignancy arises.
Osteochondroma
• Osteochondroma (osteocartilaginous exostoses), which
constitute approximately one third of benign bone tumors, are
not tumors as such but rather developmental dysplasias of the
growth plate. Osteochondroma presents as a solitary lobulated
metaphyseal outgrowth, polyostotic, or rarely as a familial
disorder (multiple hereditary exostosis) and consists of
mature trabecular bone with a cartilaginous cap. Common
locations are the proximal and distal femur, the proximal
humerus and tibia, and the pelvis and scapula. Radiographic
and gross changes are characteristic. Rapidly growing lesions
in adults may indicate a (rare) risk of malignant transformation
to secondary chondrosarcoma. These lesions must be
distinguished from parosteal osteosarcoma. The prognosis of
solitary exostosis is excellent, with approximately 5%
recurrence after surgical removal.
The cortex markedly thickened by addition of new bone from beneath the
periosteum in a boy with osteoid osteoma. Note that you can follow the old
cortex from below upward in the radiograph to an area about 4 centimeters in
length where it has been largely destroyed. At the center of this segment of
destroyed cortex and at a point which is also opposite the thickest part of the
newly superimposed cortical bone, there is an oval area of radiolucency. This
represented the nidus of the osteoid osteoma, seen as a reddish pulpy
projection from the wedge of bone removed at surgery.
Giant Cell Tumor
• Giant cell tumor of bone (osteoclastoma) occurs
preferentially between the ages of 20 and 40 years. Typically,
the lesion is located at the epimetaphyseal junction of long
bones such as the femur, the tibia, the humerus, the radius, and
the fibula, presenting as a slowly growing lytic lesion causing
persistent intraosseous pain, reactive effusions, and eventual
fractures. Radiographs reveal large radiolucent lesions with
surrounding reactive bone formation, cortical thinning,
trabecularization, and bony separation. Grossly, they appear as
soft, friable, reddish-brown tissue resembling a bloody sponge.
There may be areas of aneurysmal cavitation. Microscopically,
they show a mixedcell proliferation of stromal mononuclear
cells and multinucleated (osteoclastic) giant cells in a
markedly vascularized stroma and focal hemorrhages. Up to
10% (usually the incompletely removed tumors) metastasize;
the neoplastic component is the mononuclear stromal cells.
Treatment by curettage alone results in 50% recurrence.
Giant cell tumor of the proximal end of the radius. There is
destruction of the cortex for several centimeters down the shaft, but of
varying degree. The tumor has not destroyed all the spongy bone
within the head of the radius close to the joint surface.
Giant cell tumour. Eccentric expanding lytic
lesion which has thinned the cortex crossed
by strands of bone. The subarticular position
is characteristic of this tumour.
Primary malignant tumours
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On plain films, primary malignant tumours usually have poorly defined margins,
often with a wide zone of transition between the normal and abnormal bone. The
lesion may destroy the cortex of the bone. A periosteal reaction is often present and
a soft tissue mass may be seen.
Radionuclide bone scans show substantially increased activity in the lesion.
Although CT is no better than plain radiographs at making a diagnosis, CT scans can
be used to show the extent of a tumour. Extension within the marrow cavity can be
recognized by increased density of what should normally be a density close to that
of fat. Extension into the soft tissues can be accurately defined, as can the
relationship to important nerves and arteries.
Similar information can be obtained using MRI with the advantage that images may
be produced in the sagittal or coronal planes and bone marrow and soft tissue
involvement is more acurately demonstrated. Magnetic resonance imaging is
therefore the best imaging tool for determining the local extent of the primary
tumour.
Osteosarcoma (osteogenic sarcoma) occurs mainly in the 5-20-year-old age group,
but is also seen in the elderly following malignant change in Paget's disease. The
tumour often arises in a metaphysis, most commonly around the knee. There is
usually bone destruction with new bone formation and typically a florid spiculated
periosteal reaction is present, the so-called 'sunray appearance' . The tumour may
elevate the periosteurr to form a Codman's triangle.
Primary malignant tumours
• Chondrosarcoma occurs mainly in the 30-50-year-old agt group, most commonly
in the pelvic bones, scapulae humeri and femora. A chondrosarcoma produces a
lytic expanding lesion containing flecks of calcium, a sign thai indicates its origin
from cartilage cells. It can be difficult tc distinguish from its benign counterpart,
the enchondroma, but a chondrosarcoma is usually less well defined in at least one
portion of its outline and it may show a periostea! reaction. Pelvic
chondrosarcomas often have large extraosseus components best seen with CT or
MRI. A chondrosarcoma may arise from malignant degeneration of a benign
cartilagenous rumour.
• Fibrosarcoma and malignant fibrous histiocytoma are rare bone tumours with
similar histological and radiological features. They most often present in young
and middle-aged adults, usually around the knee. The feature on plain radiographs
is an ill-defined area of lysis with periosteal reaction. Frequently the cortex is
breached. There are no imaging features that distinguish these tumours from
metastases or lymphoma.
• Ewing's sarcoma is a highly malignant tumour, commonest in children, arising in
the shaft of long bones. It produces ill-defined bone destruction with periosteal
reaction that is typically 'onion skin' in type.
• Giant cell tumour has features of both malignant and benign tumours. It is locally
invasive but rarely metastasizes. It occurs most commonly around the knee and at
the wrist after the epiphyses have fused. It is an expanding destructive lesion
which is subarticular in position. The margin is fairly well defined but the cortex is
thin and may in places be completely destroyed.
Sarcoma of the tibia. Here the rate of growth has certainly been faster,
and the entire medial cortex was destroyed before a fracture of the
bone occurred. The ragged appearance of the destructive border is
much more in keeping with the progress of a malignant tumor than the
smooth erosion allowing time
Osteosarcoma
Osteosarcoma (osteogenic sarcoma) is the most common
malignant bone tumor, occurring in endosteal, cortical or
parosteal juxta-cortical forms, usually during the second
decade of life. Most frequent sites (75%) are metaphyseal
areas adjacent to knee or shoulder (e.g., tibia, fibula, humerus),
hands, feet, skull and jaws. Radiographs show localized lytic
or osteoblastic lesions with fuzzy borders and prominent
subperiosteal reactive bone formation (Codman triangle).
The cut surface depends on the histologic variant of the tumor:
it is whitish soft or bony hard, pseudocystic with focal
necroses or hemorrhages and freely invades into adjacent soft
tissues. Parosteal OS may resemble exostoses with welldifferentiated bone or fibrous tissue components. Histologic
variants include degrees of differentiation of chondroblastic
areas or of giant cell components and overtly telangiectatic or
fibroblastic forms. OS readily metastasizes into the lungs and
pleura, less frequently to other organs.
a
c
Osteosarcoma
(osteogenic
sarcoma)
Magnetic
resonance imaging of bone tumours, (a) Tl-weighted
scan of osteosarcoma in the lower shaft and metaphysis
of the left femur. The extent of tumour (arrows) within
the bone and the soft tissue extension are both very well
shown. This information is not available from the plain
film (b), although the plain film provides a more
specific diagnosis, because the bone formation within
the soft tissue extension (arrows) is obvious, (c) T2weighted scan of lymphoma in the T10 vertebral body
(arrow). The very high signal of the neoplastic tissue is
very evident even though there is no deformity of shape
of the vertebral body.
b
Chondrosarcoma
• Chondrosarcoma arises from cartilage rests or preexisting
ECs. There are several gross variants: central, juxtacortical and
peripheral (the latter arising outside the bone). CSs occur in
older persons with a peak in the sixth decade of life, usually in
central portions of the skeleton such as shoulder, pelvis,
proximal femur and ribs. Radiographic images show a bulky
osteodestructive lesion with a characteristic pattern of
calcification ("salt and pepper" or "popcorn"). Gross lesions
show a smooth whitish glistening cut-surface that is
occasionally lobulated and focally calcified. Histologic
appearances vary from well differentiated cartilaginous tumors
to undifferentiated and mesenchymal forms. Welldifferentiated OS can be hard to distinguish from EC. Criteria
of malignancy are the grouping and polymorphism of
chondrocytes, their nuclear atypia, multinucleate cells and
occasional mitoses. CSs metastasize preferentially to the lungs.
Chondrosarcoma - slow-growing malignant bone tumor which characteristically
shows calcification within the tumor. The illustrations on the left are show the
effect on the upper femur of a chondrosarcoma which is growing principally
outside the bone. The illustrations on the right are from a patient whose tumor
began inside the bone and grew slowly enough to expand it.
a
b
c
d
Chondrosarcoma. (a) Plain film shows a large mass containing calcification arising from the pubic
ramus. (b) CT shows the large mass containing calcium. There is also displacement of the bladder (B)
and rectum (R). (c) Axial MRI scan at the same level. Note that the calcification gives no signal, (d)
MRI scan at a lower level showing the tumour extending into the glutei muscles
Ewing Sarcoma
Ewing sarcoma (ES), after OS the second most
common bone tumor in children, accounts for
approximately 5% of all bone tumors and has a peak
incidence in the second decade of life. Although its
histogenesis remains unclear, frequent genetic
mutations suggest a relationship of malignant cells in
ES to primitive neuroectodermal cells. Unlike other
bone tumors, ES frequently presents with fever and
pain simulating an inflammatory disease. The
diagnosis is confirmed by biopsy and microscopic
investigation. The characteristic dense small cell
tumors must be distinguished from cell tumors such
as neuroblastoma and malignant lymphoma. Long
bones including midshaft humerus, tibia and femur
are the sites most frequently affected. Grossly, the
tumor impresses as osteolytic soft grayish-white
masses with focal hemorrhage which may penetrate
the periosteum and invade adjacent soft tissues. ES
commonly metastasizes to lungs, brain and other
bony sites such as the skull.
Osteoblastic metastases in the wing
of the ilium. Such increased density is
caused by new bone formation locally.
Malignant metastases from carcinoma
of the prostate most frequently
produce osteoblastic foci in bone.
Osteolytic metastases in the
upper femur. Decreased density
due to destruction by growing
tumor is usual in metastases from
kidney, lung, and thyroid.
Joints
• The plain film examination remains important for
imaging joint disease, but MRI is being used with
increasing frequency to show meniscal and
ligamentous tears in the knee, rotator cuff tears
of the shoulder and avascular necrosis of the
hip. Arthrography involves injecting contrast
medium into the joint space directly and taking
plain films or CT scans. The main use of
arthrography is to demonstrate meniscal tears of
the knee and occasionally rotator cuff tears of
the shoulder, but it has been largely replaced by
MRI.
Plain film signs of joint disease
• Synovial joints have articular surfaces covered
by hyaline cartilage. Both articular and
intraarticular cartilage (such as the menisci in
the knee) are of the same radiodensity on plain
films as the soft tissues and therefore are not
visualized as such; only the space between the
adjacent articular cortices can be appreciated .
The synovium, synovial fluid and capsule also
have the same radiodensity as the surrounding
soft tissues and, unless outlined by a plane of
fat, cannot be identified as discrete structures.
The articular cortex forms a thin, well-defined
line which merges smoothly with the remainder
of the cortex of the bone.
Signs indicating the presence of
an arthritis.
Joint space narrowing is due to destruction of articular cartilage. It occurs in
practically all forms of joint disease, except avascular necrosis.
Swelling of the soft tissues around a joint may be seen in any arthritis
accompanied by a joint effusion and whenever periarticular inflammation is
present. It is, therefore, a feature of inflammatory, and particularly infective,
arthritis. Discrete soft tissue swelling around the joints can be seen in gout
due to gouty tophi.
Osteoporosis of the bones adjacent to joints occurs in many painful conditions.
Underuse of the bones seems to be an important mechanism, but is not the
only factor. Osteoporosis is particularly severe in rheumatoid and
tuberculous arthritis.
-Response to the deposition of urate crystals in gout.
-Destruction caused by infection:
-pyogenic arthritis.
-tuberculosis.
-Synovial overgrowth caused by repeated haemorrhage in haemophilia and
related bleeding disorders.
-Neoplastic overgrowth of synovium, e.g. Synovial sarcoma.
Signs that point to the cause of
an arthritis
• Articular erosions
• Osteophytes, subchondral
sclerosis and cysts
• Alteration in the shape of the joint
Early rheumatoid arthritis. Small erosions
are present in the articular cortex (arrows)
and there is soft tissue swelling around the
proximal interphalangeal joints.
Advanced rheumatoid arthritis
(arthritis mutilans). There is
extensive destruction of the
articular cortex of the
metacarpophalangeal joints with
ulnar deviation of the fingers.
Fusion of the carpal bones and
wrist joint has occurred.
Osteoarthritis is the commonest form of arthritis. It is
due to degenerative changes resulting from wear and
tear of the articular cartilage. The hip and the knee are
frequently involved but, despite being a weight-bearing
joint, the ankle is infrequently affected. The wrist, joints
of the hand and the metatarsophalangeal joint of the big
toe are also frequently involved.
In osteoarthritis can usually be seen:
Joint space narrowing. The loss of joint space is maximal in the
weight-bearing portion of the joint; for example, in the hip it is
often maximal in the superior part of the joint, whereas in the
knee it is the medial compartment that usually narrows the most.
Even when the joint space is very narrow it is usually possible to
trace out the articular cortex.
Osteophytes are bony spurs, often quite large, which occur
at the articular margins.
Subchondral sclerosis usually occurs on both sides of the joint; it is
often worse on one side. Subchondral cysts may be seen beneath
the articular cortex often in association with subchondral
sclerosis. Normally, the cysts are easily distinguished from an
erosion as they are beneath the intact cortex and have a sclerotic
rim but occasionally, if there is crumbling of the joint surfaces,
the differentiation becomes difficult.
Loose bodies are discrete pieces of calcified cartilage or bone lying
free within the joint, most frequently seen in the knee. It is
important not to call the fabella, a sesamoid bone in the
gastrocnemius, a loose body in the knee joint.
Osteoarthritis and rheumatoid arthritis are the two types of
arthritis most commonly encountered.
METABOLIC BONE DISEASES
• Metabolic bone diseases include diseases of increased bone resorption,
such as osteoporosis, and of calcium metabolism, such as rickets,
osteomalacia, hyperparathyroidism, and renal osteodystrophy. Primary
osteoporosis is an age-related disorder preferentially affecting women
that ultimately may cause a loss oi 35% to 50% of cortical or trabecular
bone mass. It is related to hormonal influences (e.g., estrogen deficiency),
reduced physical activity, and nutritional and genetic factors. Secondary
osteoporosis follows a large variety of diseases, including malabsorption
or malnutrition, endocrine disorders (e.g., hyperparathyroidism or
hypoparathyroidism, hypogonadism, and type 1 diabetes) and neoplastic
diseases, such as multiple myeloma and bony metastases. Disorders in
calcium homeostasis cause reduced matrix mineralization with
osteopenia. Primary and secondary hyperparathyroidism (with the latter
related to renal insufficiency) are characterized by increased osteoclastic
bone resorption with features of dissecting osteitis and osteitis fibrosa
cystica (von Recklinghausen disease of the bone)
INFECTIOUS DISEASES
• Osteomyelitis (OM), an acute or chronic inflammation of the bone
marrow cavity and bone, usually has an infectious cause. OM may
originate from hematogenous spread of infectious organisms (i.e.,
secondary to pyemia or septicemia) or from their direct invasion
through penetrating wounds (including from orthopaedic
procedures) or open fractures. Despite readily available antibiotic
drugs, infectious OM still constitutes a serious clinical problem for
several reasons: First, OM is rarely a primary disease but more often
a complication of an undiagnosed or inadequately treated infection.
Second, OM responds poorly to antibiotic treatment (causative
organisms may be drug resistant) and may run a chronic course with
complications such as amyloidosis. Third, OM may be the source of
additional hematogenous spread causing septic shock, hemorrhage,
or abscesses in vital organs (brain, myocardium). Therefore,
treatment must be radical, combining antibiotic and surgical
intervention.
NONINFECTIOUS ARTHRITIC
DISEASES
• Osteoarthritis (OA) is an extremely common cause of disability,
especially in people aged older than 75 years, 85% of whom
show clinical evidence of the disorder. Despite its ubiquity,
primary OA is of unknown etiology, although it is thought to
result from intrinsic defects of cartilage. Abnormal mechanical
forces on the cartilage, decreased water bonding of cartilage,
increased stiffness of subcartilaginous bone, and biochemical
abnormalities such as decrease in proteoglycans and shortening
of glucosaminoglycans have been implicated. The latter
decreases cartilaginous water binding in favor of its binding by
collagen fibers. Mutations of the collagen type II gene may be
involved. Secondary OA occurs in patients with such underlying
causes as malformations, trauma, and metabolic diseases with or
without crystalline deposits.
PAGET DISEASE
• Excessive osteoblastic bone formation with abnormal structure and
impaired stability characterize Paget disease (PD; osteitis
deformans). After the age of 40 years, the disease increases in
incidence to affect 4% to 10% of the population, primarily in white
populations of Northern Europe, North America, Australia, and New
Zealand, more often in men than women. It may occur in a
monostotic form (in only one bony site) or in polyostotic forms
(i.e., systemically). Head bones become enlarged; patients report
headache, back pain, deafness, and visual disturbances; long bones
(especially of the lower extremities) become tender; and deformed
and fractures occur. The disease course is complicated by osteosarcoma (OS) in approximately 1% of patients.
Osteoporosis
Osteoporosis refers to a condition of reduced mass of
mineralized bone secondary to an imbalance between
catabolic (T) and anabolic (I) bone metabolism. The
loss of skeletal mass can reach a state where the
mechanical stability of affected parts is no longer
maintained and fractures occur. There are primary
and secondary forms of osteoporosis, and localized or
systemic changes are identified. The most wellknown and frequent type of primary osteoporosis is
old age osteoporosis (senile osteoporosis). Inactivity
osteoporosis (immobilization osteoporosis) is a
localized form of secondary osteoporosis
Osteoporosis: Clinical
Manifestations
• The anatomical and clinical manifestations of osteoporosis are
dependent on the maximal bone mass (peak bone mass), which is
genetically determined. It is higher in men than in women and lower
in white populations than in others. Therefore, a white female is at
highest risk. Bone mass is commonly determined by radiographic
measurement of bone density, which is highest at the ages of 25 to 35
years and decreases gradually thereafter by approximately 0.7% per
year. Gross and microscopic features of osteoporosis show a diffuse
rarefaction of trabecular bone and a symmetric thinning of trabecular
and cortical bone. The ratio of mineralized bone to osteoid remains
normal. In postmenopausal osteoporosis, disruption of trabecular bone
adds significantly to the instability of the skeleton. The most common
fractures resulting from primary osteoporosis are hip fractures,
compression fractures of vertebral bodies (8 times more frequent in
females), and fractures of the distal radius.
Rickets and Osteomalacia
• In rickets and osteomalacia, mineralization of osteoid is reduced while
bone mass remains normal. Rickets affects the growing bones of
children, and osteomalacia affects the newly formed bone matrix in
adults. Responsible metabolic disturbances are vitamin D deficiency,
phosphate deficiency, and mineralization defects. Growing bone is
severely changed in children with rickets because inadequate
mineralization of osteoid matrix leads to overgrowth and distortion of
epiphyseal
cartilage
projecting
into
the
medullary space, disruption of osteoid/cartilage replacement, and
reactive proliferation of capillaries and fibroblasts. Loss of structural
stability causes skeletal bone deformations (thoracic kyphosis, lumbar
lordosis, coxa vara, genu varum). Osteocartilaginous thickening of
ribs produces characteristic rachitic rosary. Adults with osteomalacia
experience only mild bowing of long bones; however, stress resistance
of bones is reduced, and gross or microscopic fractures
Renal Osteodystrophy
• Renal osteodystrophy, which is most common in
patients undergoing long-term dialysis tor chronic
renal failure, combines the changes of osteomalacia
with focal soft tissue, bone resorption, and vascular
calcifications are observed (metastatic calcification)
tumorlike calcium deposits in some cases. While
osteomalacic changes suggest renal tubular damage,
additional focal osteoclastic bone resorption is caused
by secondary hyperparathyroidism. Therapeutic
planning must focus on treating the chronic renal
disease, replacing 1,25(OH),-D, substituting for
hypophosphatemia,
and
partially
resecting
hyperplastic parathyroid glands.
Primary Hyperparathyroidism
• Primary hyperparathyroidism causes generalized bone resorption
by focal osteoclastic activities (as described in osteitis fibrosa
cystica) combined with an increased incidence of stone formation
(e.g., nephrolithiasis). Osteoclastic hyperactivity starts at
subperiosteal and endosteal surfaces, cutting into the bone and
replacing respective splits and holes by connective tissue (dissecting
osteitis). Areas of hemorrhage and microfracture may occur. Larger
cystic spaces occur eventually, hemorrhage expands, and resorptive
giant cell granulomas develop ("brown tumors" in osteitis fibrosa
cystica). These must be distinguished from aneurysmal bone cysts
(ABCs), giant cell tumor (GCT) of bone, and telangiectatic OS.
Characteristic radiographic changes in hyperparathyroidism are found
preferentially in the hands (radial phalanges of the second and third
fingers), with signs of focal calcinosis in the spine and the cartilage of
major joints
Osteomyelitis
• Although osteomyelitis (OM) can easily be suspected from
persistent purulent secretion from deep open wounds or
fistulas extending to the bone, the clinical manifestations of
hematogenous OM are more difficult to identify. Obscure back
pain, low-grade fever, malaise, and moderate blood
leukocytosis are among uncharacteristic general symptoms. If
localized signs appear, such as circumscribed bone pain,
reddening and swelling of the covering skin or mucus
membranes, or even fistula formation with purulent discharge,
radiographic procedures and tissue biopsies may reveal the
real nature of the disease. The most common organisms
causing OM are Staphylococcus aureus (e.g., after longstanding infected intravenous catheters, endocarditis, or
complicated wound healing), various gram-negative rods,
pneumococci (in neonates), salmonellae, and Mycobacterium
tuberculosis.
Chronic Osteomyelitis
• At the site of bacterial nesting in the bone, usually at wellvascularized metaphyseal sites, acute endotheliitis/vasculitis with
subsequent neutrophilic exudation and necrosis of adjacent bone
develops. Necrosis may follow local vascular occlusion by
thrombosis, compression and hypoxemia, or both. Infection spreads
through the marrow cavity and cortical bone, extending
subperiosteally, transperiosteally, and through soft tissues, creating
draining sinuses (fistulas). Progression to chronic OM adds focal
osteoclastic bone resorption and fibrous repair mechanisms. Bony
cavities may contain fragments of necrotic bone (bony sequester)
surrounded by hyperostotic bone (involucrum). Persistent abscesses
are surrounded by condensed sclerotic bone (Brodie abscess).
Periosteal and osteal hyperostosis on radiograph may signal
underlying chronic OM. Microscopic features include decreased
neutrophils, persistent edematous swelling, scattered plasmacytic
infiltrates, and progressive fibrosis.
Infectious Arthritis
• Infectious arthritis is an acute or chronic inflammation of a
joint or joints, usually caused directly or indirectly by specific
infectious organisms. Infectious arthritis is caused directly by
seeding of such pyogenic organisms as gonococci,
staphylococci, meningococci, and pneumococci. Infection
results in a characteristic edematous and neutrophilic
infiltration of the synovialis with hemorrhage or necrosis
(according to endotoxin or exotoxin activities) and with
subsequent
lymphoplasmacytic
infiltration,
capillary
proliferation, and fibrosis, depending on the duration of the
process. Destruction of ( artilage and fibrous adhesions may
cause final joint dysfunction and ankylosis.
Tuberculous Arthritis
• Tuberculous arthritis is characterized by granulomatous reaction and
runs a primary chronic course. It is the consequence of hematogenous
spread of organisms, usually during early or later phases of stage II
tuberculosis (early or late postprimary tuberculosis). Infection usually
affects only one joint, most frequently the spine, the hip, the knee, the
elbow, or the ankle. The onset of symptoms is insidious; frequent local
muscle spasms at night may be the first suspicious sign of the disease.
Walking may be problematic if the spine is involved (Pott disease).
Radiographic changes and strong positive tuberculin skin test results
are helpful in establishing the diagnosis. Diagnostic proof is given by
tissue biopsy and the demonstration of acid-fast bacilli in the
granulomatous inflammation as well as by culture or polymerase
chain amplification reaction (PCR) techniques
Osteoarthritis
Osteoarthritis (OA) is the most common degenerative joint
disease causing physical disabilities in persons aged older than
65 years. Initial changes, which become overt by the age of 20
years in 4% of the population, increase steadily to affect more
than 85% of persons by the age of 75 years. Primary OA is
thought to result from intrinsic defects of cartilage. Secondary
OA results from conditions such as malformations, trauma, and
metabolic diseases with or without crystalline deposits. Several
pathogenetically important factors may contribute to the
development of OA: abnormal mechanical forces on the
cartilage (increased unit load), decreased water bonding of
cartilage (decreased resilience), increased stiffness of
subcartilaginous bone, and biochemical abnormalities such as
decrease
in
proteoglycans
and
shortening
of
glucosaminoglycans. The latter decreases cartilaginous water
binding in favor oi binding by collagen fibers. Genetic factors
may favor mutations of the collagen type II gene.
Osteoarthritis:
ClinicalManifestations
• Signs and symptoms of osteoarthritis (OA)—morning stiffness and
pain, rubbing sounds (crepitus), and tenderness and swelling of sott
tissues covering joints—develop gradually, most often in the knees,
the hips, the lumbar and cervical spine, and the finger joints, leading
eventually to muscle contracture and compromised joint mobility.
Early microscopic findings are loss of cartilaginous metachromatic
staining (loss of proteoglycans), loss of chondrocytes, reactive
hypertrophy and grouping of residual chondrocytes, and fibrillation
and splitting of the cartilage surface. Fibrillation favors infiltration by
synovial fluid with further enzymatic damage, inflammation, and
cartilage destruction. Granulation tissue and fibrosis replace cartilage,
and erosions result in open bony surfaces. Reactive new bone
formation (osteophytes) and fibrous adhesions in border zones limit
movement. Circumscribed areas of destruction with fragments of
cartilage, dead bone, and synovial fluid may expand into the adjacent
bone, forming debrisladen subchondral cysts.
Rheumatoid Arthritis
• Rheumatoid arthritis (RA) is a systemic chronic progressive
inflammatory disease with symmetric involvement of small
joints. Variants are Still disease in children (juvenile arthritis)
and ankylosing spondylitis (Bechterew disease) preferentially
involving the vertebral column and the sacroiliacal joints. RA
is representative of a group of autoimmune disorders referred
to as collagen-vascular diseases, which include lupus
erythematosus, primary systemic sclerosis, polymyositis, and
dermatomyositis. The etiology of RA is unknown; however, its
pathogenesis includes genetic factors (prevalence of HLADR4 and HLA-DR1 genes and others), autoimmune reactions
(possibly postinfectious), and local factors such as mechanical
stress and specifics of tissue reactivity.
Rheumatoid Arthritis: Clinical
Manifestations
• Microscopic features of rheumatoid arthritis (RA) are
progressive villous hypertrophy of the synovialis secondary to
fibrinous swelling, proliferation of synovial lining cells, and
lymphoplasmacytic infiltration. With increasing chronicity,
acute inflammatory reactions are replaced by granulation
tissue and fibrosis covering and eroding the cartilaginous
surface of the joints (pannus formation). Joint mobility is
severely inhibited with grossly impressive deviations
(subluxation) of joints. End-stage disease is characterized by
complete fibrous obliteration of the joints. Adjacent soft
tissues may contain focal granulomas with binucleated giant
cells (Aschoff cells) surrounding soft tissue fibrinoid necrosis
(rheumatic nodule). Although 25% of patients with RA may
recover completely, 50% experience terminal severe
incapacitation. Death usually occurs from complications such
as infections, gastrointestinal hemorrhage, or cardiovascular or
pulmonary involvement.
Paget Disease
• Paget disease (osteitis deformans) is characterized by
excessive osteoblastic bone tormation with abnormal structure
and impaired stability. It occurs with increasing incidence after
the age of 40 years (4-10% of the population), primarily in
white populations, more often in men than in women. PD may
occur in a monostotic form (one bony site) or in a systemic
polyostotic form. In the initial stage, osteoclast hyperactivity
with increased lacunar bone resorption is seen; the presence of
respective inclusion bodies and viral transcripts (resembling
paramyxovirus) suggests it is stimulated by infection with a
slow virus. In the second stage, marked osteoblastic
hyperactivity compensates and then overcompensates for the
osteoclast function, and excessive disorderly new bone with
irregular cement lines (mosaic bone) is produced. The final
stage ("< old" or burnt-out phase) is characterized by marked
thickening of densely mineralized bone (osteosclerotic phase)
with minimal cellular activity.
Paget Disease: Clinical
Manifestations
• Early phases of Paget disease (PD) are asymptomatic,
although incidentally increased serum alkaline
phosphatase levels may suggest a skeletal disorder. In
more advanced cases, incidental radiographic
findings may suggest the disease. Typical features are
enlargement of head bones, headache, deafness and
visual disturbances, deformation and tenderness of
long bones (especially of the lower extremities), back
pain, and fractures (vertebra, chalk-stick-type crossfractures of long bones). OS develops in
approximately 1 % of patients.
Fibrous Dysplasia
• Fibrous dysplasia (FD) is a tumorimitating developmental
abnormality of bone that consists of circumscribed mixed fibrous
and osseus lesions. FD may be associated with endocrine
abnormalities and skin pigmentation such as precocious puberty
and cafe au lait spots (McCune-Albright syndrome),
acromegaly, Cushing syndrome. Monostotic and polyostotic
forms frequently occur in the proximal femur, the tibia, the ribs,
and the mandible. Polyostotic forms (25%) also may involve the
pelvis, the hands, or the feet. Growing lesions cause pain,
deformation of bones, and pathologic fractures. Characteristic
radiographic findings show a ground-glass, slightly
"multivesiqular" ("soap bubble") appearance with distinct
borders. Microscopy shows a dense whorled fibrous tissue
containing spicules of woven bone. The prognosis of FD is good,
and management should prevent complications such as fractures.
Rarely, malignant sarcomas may complicate the course of FD.
The localized lesion, (a) A well-defined
sclerotic edge indicating a benign lesion
- a fibrous cortical defect.
Fibrous dysplasia.
Collagen-Vascular Disease
• Collagen-vascular disease (CVD) refers to a group of systemic
autoimmune disorders with overlapping signs and symptoms that
affect several organ systems (e.g., skin, kidneys, lungs). CVDs
include systemic lupus erythematosus, RA, primary systemic
sclerosis,
dermatomyositis, polymyositis, and certain "overlap
syndromes". Although the etiologies of CVDs are unknown, the
pathogenesis is characterized by various autoimmune reactions
with demonstration of respective autoantibodies, circulating
immune complexes, or both. The essential pathologic features in
.ill
CVDs
are
chronic
inflammatory
infiltration
(lymphoplasmacellular) ot connective tissue, edema, fibrinoid
necroses, vasculitis, and progressive fibrosis. The extent and
composition of these features vary among the different CVDs
and with their type of autoimmune reaction (autoantibodies,
circulating immune complexes, T-cell immune reaction).
Compartment Syndrome
Compartment syndrome (CS) results from increased pressure in one
or more (osteo) fascial compartments. Sustained increase of tissue
pressure from local edema reduces capillary perfusion below the
level necessary for sustaining tissue viability; irreversible muscle
and nerve damage results in a few hours. Partial burial, trauma,
burns, or exercise may cause CS. Pathogenetic mechanisms are increased fluid accumulation, decreased tissue volume (compartment
constriction), and restricted volume expansion secondary to external
compression (e.g., casts). In conscious patients, pain is
disproportionate to the obvious injury and increases with passive
stretching of muscles. Loss of sensation from nerves running
through affected compartments may occur. Microscopic changes are
intense soft tissue edema with progressive degeneration and
necrosis, hemorrhage, and, in delayed cases, slowly developing
granulation tissue and fibrosis. There is high risk of superinfection,
and secondary septicemia exists.
SOFT TISSUE DISORDERS
• Soft tissue refers to the widely distributed interstitial tissue of
mesodermal origin filling spaces between ectodermal,
endodermal, and skeletal structures. It includes differentiated
tissues such as fibrous tissue, fat, and skeletal muscle.
Although all pathologic reaction patterns are represented in
diseases of soft tissue, including necrosis and degeneration,
infection and inflammation, and hyperplasia and neoplasia,
only a few examples can be discussed here. We focus on such
important disorders as compartment syndrome, collagenvascular diseases (CVDs), and benign and malignant tumors.
Benign Soft Tissue Tumors
• Benign tumors of soft tissue may occur at any age and are
classified according to the tissue where they arise: fibromas,
lipomas, rhabdomyomas, leiomyomas, or mixtures of these,
and composite tumors with additional tissue components
(angiolipomas,
fibrous
histiocytoma,
neurofibroma,
myelolipoma). Subcutaneous lipomas, the most frequent benign
tumors, are slowly enlarging well-circumscribed yellowish
masses with a histology indistinguishable from normal fat tissue.
Fibrous tumorlike lesions (nodular fasciitis, fibromatosis) are not
considered real tumors, although some show locally aggressive
behavior. Fibrous histiocytomas are dermal tumors of
interlacing fibrous strands and collections of lipidand
ironcontaining histiocytes. Benign neurofibromas occur in
dermis and in part in the submucosa of the alimentary tract. They
may cause bleeding or mild obstruction. Leiomyomas are
common in the uterus but also are found in the gastrointestinal
tract or originating from blood vessels.
Malignant Soft Tissue Tumors
• Sarcomas spread by hematogenous metastases rather than through
lymphatic channels. They are classified according to the tissue
from which they derive, or in a more descriptive way if their
histogenesis is unclear. Variants include liposarcomas,
fibrosarcomas, malignant fibrous histiocytoma (MFH),
neurofibrosarcomas, rhabdomyosarcomas, leiomyosarcomas, and
alveolar soft part sarcomas or epithelioid sarcomas. Fibrosarcoma,
usually arising from fascia, tendons, periosteum, or scar tissue of
the thigh, the knee, or the trunk, is not a common malignancy, but
its "pleomorphic cousin," MFH, is the most common soft tissue
sarcoma. MFH is a highly malignant tumor of deep fascia, skeletal
muscle, and the retroperitoneal space, preferentially occurring in
patients aged 50 to 70 years. Postradiation fibrosarcoma is
classified as MFH. Prognosis depends on the degree oi atypia and
the polymorphism of its cells. Approximately 50% of MFHs
metastasize early to the lungs. Liposarcomas arise preferentially in
the deep subcutaneous tissues
Malignant Soft Tissue Tumors
(continued)
of the thighs, the abdomen, and the retroperitoneum of persons
aged older than 50 years. There are several morphologic variants
(e.g., well-differentiated, myxoid, pleomorphic, and round cell
forms), some of which show mutational chromosomal
abnormalities of their adipocytes. Rhabdomyosarcoma is a
tumor of children and young adults. It is thought to derive from
primitive mesenchyme or embryonic muscle tissue and has
corresponding appearances: embryonal rhabdomyosarcoma,
alveolar
rhabdomyosarcoma,
and
pleomorphic
rhabdomyosarcoma. Well-differentiated forms contain plump
cells resembling striated muscle. Leiomyosarcomas are
malignant tumors of smooth muscle, occurring most commonly
in the uterus and gastrointestinal tract. Neurofibrosarcoma and
neurolemmal sarcoma (malignant schwannoma) are tumors of
peripheral nerves that are more common in adults. Epithelioid
sarcomas and alveolar soft part sarcomas are rare, highly
malignant tumors of uncertain histogenesis.