chapter 2 medical imaging
TRANSCRIPT
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2 Medical Imaging
Randy E. Cohen, DP M
C o n t e n t s
2.1 Computed Tomography (CT) . . . . . . . . . . . . . . 34
2.2 Magnetic Resonance Imaging (MRI) . . . . . . . . 34
2.3 Bone Scan . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4 Bone Tumors . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.5 Osteomyelitis . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.6 Rheumatology . . . . . . . . . . . . . . . . . . . . . . . . 44
2.7 Osteochondrosis. . . . . . . . . . . . . . . . . . . . . . . 46
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2.1 Computed Tomography (CT)
Advantages over Conventional Radiology
Cross sectional display
Excellent density resolution
CT Numbers (Hounsfield Units HU) Bone < 1000 white (radiodense)
Air -1000 black (radiolucent)
Window Width and Window Level
Window width is the variations in gray
Window level is the mid point in gray
For evaluating bone pathology we use window widths of 400 or more and window levels of 50 or more. For
evaluating soft tissue pathology we use narrower window widths of 100-200 and lower window levels of 20-50.
To enhance contrast in soft tissue pathology iodine based dye is used. CT is superior to MRI in evaluating ossi-
fication, calcification and cortical bone. It is useful in evaluating articular disorders but not as accurate as MRI. CT
is excellent to evaluate osseous coalitions. It can be used to evaluate the extent of soft tissue and osseous involvementin infections, but it is not tissue specific. For neoplasms it adds additional information that improves diagnostic
accuracy.
2.2 Magnetic Resonance Imaging (MRI)
There is no ionizing radiation. A strong magnetic field and radio waves are used to produce the image.
Spin density = hydrogen concentration
TR = repetition time
TE = time to echo
T1 = short TR and short TE good for anatomy
T2 = long TR and long TE good for pathology
Increased signal intensity means bright or white. Decreased signal intensity means dark or black. STIR scans orfat suppression scans turn the fat black enhancing contrast in the bone marrow and soft tissue. Gadolinium is a
paramagnetic contrast enhancing agent.
Advantages of MRI
Cortical bone is invisible
Bone marrow visualizes well
Better soft tissue contrast than CT
Moving blood acts as a contrast medium
Disadvantages of MRI
Exam takes a long time
Large magnets take up space and are expensive
Requires wide area free of metallic material
Magnetic materials in the body preclude scanning
Cardiac pacemakers preclude scanning
Claustrophobia precludes scanning
Tissue appearance on MRI
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Molecules with strong molecular bonds such as ossification or calcification will not image well on MR giving a
low signal intensity. Molecules with low water content such as ligaments will also give a low signal intensity.
MR imaging provides superior soft tissue contrast without ionizing radiation. It is the most tissue specific diag-
nostic modality we have short of biopsy.
2.3 Bone Scan
A bone scan is highly sensitive but non-specific. It can detect osteogenesis well before it will show up on an x-
ray. A bone scan is useful and effective for early detection of stress fractures and osteomyelitis. It can accurately eval-
uate delayed and non-union.
In atrophic non-union of fractures there is diminished uptake at both ends of the fracture site as well as a gap
in between. In hypertrophic non-union there is increased uptake at both ends of the fracture site with a clear gap in
between. Delayed union will show up as diminished uptake.
Pagets disease has a characteristic appearance on bone scans. Pagets has 3 stages: lytic, blastic, and quiescent. Inthe lytic stage the bone scan shows no increased uptake. In stage two, the blastic stage, there is confluent uptake
starting at the end of the bone. Focal uptake is rare. In the third stage there is no increased uptake. Metastatic CA
usually presents with focal uptake.
2.4 Bone Tumors
Unicameral Bone Cyst (Solitary)
A membrane lined cavity containing a clear yellow fluid
Occurs most often in children 4-10 years of age
Lesions remain asymptomatic unless complicated by fracture
They enlarge during skeletal growth and become inactive, or latent, after skeletal maturity
Active Type
Develops in patients under 10 years of age
Cyst arises adjacent to growth plate and may grow to fill most of metaphysis
Bone may be slightly expanded within cortical shell
May cause pathologic fracture
Tissue Appearance on MRITissue T1weighted T2weighted
Cortical Bone dark dark
Calcification dark dark
Ligaments dark dark
Large Vessels dark darkFibrosis dark dark
Chronic Hemorrhage white white
Fat white gray
Muscle gray dark
Acute Hemorrhage gray black
Hemosiderin black black
Exudate gray white
Edema gray white
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Passive Type
Patients are usually over 12 years of age
Cysts cease to expand
Have thicker bony wall than active lesions
May show evidence of healing or ossification
Less likely to result in fracture
Predilection for the Metaphysis of Long Bones
Proximal humerus (50% of cases)
Proximal tibia
Proximal femur (40%)
Radiographic
Show a central, well marginated and symmetric radiolucent defect in metaphysis
Usually no bony separations or loculations
Thin rim of non-reactive bone borders the unicameral bone cyst
Treatment
Goal of treatment is prevention of pathologic fracture
Simple cysts are treated with curettage and bone grafting Recurrence is high for active cysts (50%) and low for latent cysts (10%)
Conventional teaching is that the cyst will heal and resolve if a fracture occurs through the cyst
Steroids:
80=200 mg of rnethylprednisolone infused into cavity
The failure in weight-bearing bones was high
Autologous bone marrow injection multiple drill holes
Aneurysmal Bone Cyst
An uncommon expansile osteolytic lesion of bone consisting of a proliferation of vascular tissue that forms a
lining around blood filled cystic lesion
Develops in metaphyseal region of long bones, pelvis, vertebral body Most aneurysmal bone cysts occur in patients under 20 years of age, and it is uncommon after 30 years of age
Grows rapidly and may attain considerable size
Commonly involves the proximal humerus, femur, tibia, and pelvis
Can cause paraplegia when it involves the vertebrae
Radiographic
Radiolucent lesion with expanded cortex arising in the medullary canal of the metaphysis
Aneurysmal expanded appearance of cortex is contained by periosteum and thin shell of bone
Marked cortical thinning and erosion and periosteal elevation
Lesion rarely penetrates the articular surface or growth plate
Diagnostic
CT scan
Has a density of about 20 Hounsfield units
Spine: CT scan shows a cystic lesion not appreciated on the radiograph
Bone Scan
Shows intense uptake in the margin of the lesion with normal background or decreased uptake in its center
Treatment
Curettage and bone grafting has a 20%-40% recurrence rate
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Recurrence can be managed with more aggressive curettage or excision
Marginal excision or wide excision with bone grafting is preferable
With pathologic fracture, successful resection may be difficult
Osteoid Osteoma
Benign osseous tumor usually less than 1.5 cm in diameter
Comprising 11% of all benign hone tumors
Occurs primarily in adolescents and less often in children
Is rare in patients over 40 years of age
Presenting symptom is well localized pain, which may be more severe at night and is relieved by aspirin or
other prostaglandin inhibitors
Because osteoid osteoma is a vascular tumor, substances that cause vasodilitation such as alcohol may
precipitate an acute pain crisis
Most common site is proximal femur and diaphysis of long bones
Less often: foot (talus, navicular, or calcaneus) and in posterior spine
Radiographic
Intense bony reaction to small nidus is hallmark of osteoid osteoma, however, may be difficult to see on
x-rays
Look for oval radiolucent nidus only 3-5 mm in diameter that is surrounded by disproportionally large
dense reactive zone
Although usually located in cortex, nidus may occur subperiosteal and endosteal regions
Radiographic Differential Diagnosis
Garres osteomyelitis (chronic sclerosing osteomyelitis)
Brodies abscess
Stress fracture
Bone Scan
Bone scans usually shows moderate or intense radioisotope uptake
Treatment When nidus is located in a low stress area such as metaphysis, treatment should consist of en bloc excision
with surrounding small block of reactive bone
Tetracycline localization:
Using tetracycline at a dosage of 4 mg/kg, four times daily, two days preoperatively, the nidus will have a
golden yellow fluorescence; the OR must be dark in order to see it
Percutaneous radiofrequency coagulation
Involves percutaneous insertion of a biopsy needle under CT scan guidance
A tissue biopsy is taken in order to prove that the needle is properly located
Then a radiofrequency electrode with a 5 mm exposed tip is introduced through the cannula
The electrode is connected to a radiofrequency generator which raises the temperature of the tip to 90C
(which is maintained for 6 minutes)
Osteoblastoma
Unusual benign osseous tumor
It resembles osteoid osteoma but is usually larger (>2 cm)
Occurs in older adolescents and young adults
Usually does not cause localized night pain, and when pain occurs, pain is usually not relieved by ASA
Intense bony reaction that is seen with osteoid osteoma, does not occur with osteoblastoma
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More often located in the posterior elements of vertebra
Will not resolve spontaneously
Sites of involvement: spine, femur, bones of the foot
An associated soft tissue mass may be seen in about 25% of patients
Malignant transformation is possible (rare)
Radiographic Show radiolucent lesion which is surrounded by a thin margin of reactive bone that may have expanded
(aneurysmal appearance)
Appear as a radiolucent defect with a central density due to ossification
Treatment
En bloc marginal excision is treatment of choice
Active tumors are more likely to recur if intracapsular resection is performed
Fibrous Dysplasia
Clinical Presentation;
Lesions may occur in one bone (monostotic) or in many (polyostotic)
Occasionally, a child may present with pathologic fracture or angular deformity
Polyostotic Fibrous Dysplasia:
Children present around 10 years of age
Findings include pain, pathologic fracture, limp, or limb deformity
In general osseous abnormalities present before 20 years of age
Lesion of bone that results in a haphazard mixture of immature fibrous tissue and small fragments of
immature irabecular bone
Angular deformities may result from defective mineralization of immature dysplastic bone
Affected bone becomes widened and adjacent cortical bone becomes thin
Radiographic
Appearance of lesions is variable but most often will show:
Intramedullary diaphyseal lesion that blends with thinned, bulged cortex Hazy or ground glass lesion which may occur with angular deformity
Angular deformity in bone is often present at the level of lesion
Sites of Involvement
Rib is involved most often but any bone can be involved; also seen in proximal femur, proximal tibia,
and mandible
Bone becomes deformed by multiple stress fracture which may eventually lead to pathologic fracture
Cystic type of lesion: radiolucent with a reactive rim, no trabeculae, and normal cortical thickness
Pagetoid type of lesion: trabecular pattern which is more dense than normal bone
Shepards crook deformity: extensive involvement of proximal femur results in a characteristic varus
deformity which resembles a Shepards crook
Nonossifying Fibroma
Also known as fibrous cortical defect
Most common bone lesion (40% children)
Results from defect of periosteal cortical bone development which leads to a failure of ossification
Lesion typically develops in childhood and adolescence
During adolescence, nonossifying fibroma is an active Stage two lesion that persists or enlarges throughout
childhood
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With skeletal maturation, it becomes latent and either regresses or ultimately ossifies
When tumor occupies > 50% of diameter of bone, it is prone to fracture
Radiographic
Well marginated radiolucent lesion, with a distinct multilocular appearance
Is usually irregular and is surrounded by reactive rim of bone
Benign cortical thinning, erosion, slight expansion There are two subtypes:
Fibrous Cortical Defect (more common lesion), is small < 0.5 cm radiolucency within cortex with
sharply defined cortex
Metaphyseal Defect (lesion commonly develops in metaphysis of distal femur, in 90% of cases, or the
distal tibia and is eccentrically located). The cortex may bulge over the lesion, as lack of remodeling and
may be surrounded by a well-defined thin rim of reactive bone. No periosteal reaction is seen unless
there has been a fracture.
Nonossifying fibroma can act as a stress riser in bone, which can lead to stress fracture with heavy running and
this will result in pain and increase uptake on bone scan. In children, closed treatment is the treatment of choice in
most cases.
Enchondroma
Benign and asymptomatic cartilaginous tumor of bone, which most often occurs in adolescents or young
adults
Is an intramedullary cartilage lesion located in central metaphysis
Intramedullary tumor develops in adjacent metaphysis and may eventually penetrate the diaphysis
Results from failure of normal endochondral ossification below the growth plate and represents a dysplasia of
the central growth plate
If dysplastic process occurs in lateral growth plate, resulting tumor is called osteochondroma
Most often affects small tubular bones of hands or feet (40%-65%)
Frequent cause of pathologic fracture
Most frequently involves the proximal phalanx, followed by the middle phalanx and the metacarpals
Transformation
Enchondroma usually become latent in adulthood and < 2% of asymptomatic solitary enchondromas will
transform to chondrosarcoma
Enchondromas of long bones have higher chance for malignant transformation
In enchondromatosis, risk of malignant transformation is about 10%-25%
In Maffucci disease (multiple enchondromas and hemangiomas) risk is near 100%
Radiographic
Central radiolucent lesion with well defined minimally thickened bony margin
During active phase in adolescence, the lesion may slowly enlarge
In children, cortex is usually thin and the lesion is radiolucent
As lesion matures, it develops a reactive marginBone Scans
Demonstrate radioisotope uptake in margin, related to activity of lesion
While there is moderate uptake in the active phase there will also be some activity in latent phase
Treatment
Asymptomatic solitary enchondromas may be followed non-operatively with serial radiographs prognosis
for benign enchondroma is excellent
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Giant Cell Tumor
A common benign but locally aggressive lesion of unknown etiology
Occurs chiefly in men between 20 and 50 years of age (after epiphyseal closure);
Tumor is an expansile, lytic lesion that involves the epiphysis and metaphysis
Tumor may erode & penetrate subchondral bone, articular cartilage and cruciate ligaments
Radiographic Large radiolucent lesion surrounded by distinct margin of reactive bone
Often the lesion is eccentric
Cortical thinning, endosteal erosion, and trabecularization or bony septation, of the cavity are associated
findings
Lesion will aggressively destroy medullary and cortical bone
Scalloping and ridges in the wall of the tumor give it a soap bubble appearance on the radiograph
Treatment
Due to proximity to articular cartilage, excision of GCT of bone is difficult
Because intra-lesional excision of GCT tends to leave tumor cells behind, past attempts of excision had
been associated with a high recurrence rate (40%)
Stage 1 or 2 lesions Intra-lesional excision is treatment of choice
Use of phenol, polymethacrylate, and liquid nitrogen
Phenol can be extremely toxic and, if used at all, its concentration should be limited to 5%
Recurrent or stage 3 lesions
En bloc excision with wide margin along with appropriate reconstruction
5% of patients will have pulmonary metastases
Tumor is considered benign-ii if pulmonary lesions are histologically benign
Pulmonary lesions may be cured with surgical resection
Osteochondroma
A developmental dysplasia of peripheral growth plate, which forms a cartilage capped projection of bonefound near metaphyses of long bones
It is the most common benign bone tumor
Usually occurs in long bones, but may occur in any bone that is preformed in cartilage
Tumor will continue to enlarge during skeletal growth, but will become latent at skeletal maturity
The lesion may continue to grow into the third decade
Occasionally a lesion grows more rapidly than expected
Most common locations are proximal or distal femur, proximal humerus, proximal tibia, pelvis, and scapula
In areas other than the knee, more likely to undergo malignant degeneration
Risk of sarcomatous transformation in solitary exostosis is about 1%, but in multiple hereditary exostoses,
the risk approaches 10%
Clinical presentation Firm, non-tender, immovable mass arising near end of the long bone
A symptomatic lesion may be caused by irritation of overlying soft tissues which may go on to form a fluid
filled bursa
Bursal fluid may be mistaken for a soft tissue mass
Radiographic
Exostosis is either fiat, sessile lesion, or pedunculated
pedunculated osteochondromas are oriented in proximal direction
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X-ray hallmark is blending of tumor into underlying metaphysis
Cartilaginous cap displays irregular areas of calcification
Treatment
No treatment is required if the diagnosis is not in doubt and if the patient is relatively asymptomatic
Surgical resection is indicated for persistent irritation (from bursitis) or for neurovascular compromise
Surgical resection is also indicated for continued osteochondroma growth after skeletal maturity
Chondroblastoma
Most common primary epiphyseal tumor in children
The adults counterpart of chondroblastoma is giant cell tumor
Most common location is proximal tibial epiphysis and proximal humeral epiphysis
Differential Diagnosis
Only three tumors may invade physis:
Chondroblastoma
Giant cell tumor
Clear cell chondrosarcoma
Clinical Presentation Painful: motion limiting, benign tumor arising during adolescence
Majority are active Stage 2 lesions
Most lesions occur in the proximal part of the tibia (17%) and the proximal part of the humerus (15%)
The hands and feet are the sites of 10% of chondroblastoma with the tumors having a particular
predilection for the talus and calcaneus
Chondroblastoma is the most common tumor affecting the patella, followed by giant cell tumor
Radiographic
Epiphyseal radiolucent lesion with fine punctate calcifications
Oval osteolysis located eccentrically in the epiphysis
Tumor is usually bordered by a well defined margin of reactive bone
Stage 3 chondroblastoma may extend through growth plate into metaphysis or through articular cartilageinto the joint
Treatment
Stage 2
Wide excision is the treatment of choice, if technically possible
It is important to avoid joint penetration because chondroblastoma cells will grow in joint fluid
Addition of methylmethacrylate to defect may be added to curettage to prevent recurrence
Stage 3
Stage 3 will require en bloc excision
These may metastasize to the lungs
Patients with lesions around the hip (proximal femur, greater trochanter, and pelvis) are significantly more
likely to develop recurrences as well as metastatic lesions
Chondromyxoid Fibroma
Locally painful benign cartilaginous lesion of bone
Occurs in adolescents
Located in metaphysis of major long bones
This lesion most often presents as an active Stage 2 lesion that is are locally destructive and has a high
recurrence rate (up to 25%)
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Does not undergo malignant transformation
Eccentric radiolucent defect with NO calcification
Adjacent cortex may be expanded, thinned or even absent
Look for sclerotic and scalloped rim
Typically located in the metaphyseal region of long bones and in some cases it is possible for it to invade the
epiphyseal plate
Treatment
Curettage is indicated for well encapsulated Stage 2 lesions
Stage 3 lesions, most often seen in the pelvis, require wide excision to prevent recurrence.
Chondromyxoid Fibroma Chondrosarcoma
Malignant cartilaginous tumor of bone
It is less common and less aggressive than osteosarcoma
Chondrosarcoma
Primary
Most often presents as a low grade - intracompartmental lesion
They are slow to metastasize and may grow to immense proportions
Tumor tends to destroy bone and to extend into the soft tissues
Tumor may invade blood vessels and produce a long intravascular tumor that may extend into heart and
pulmonary arteries
Long-term survival rate of patients with treated chondrosarcoma is between 50%-75%
Primary form occurs most often in men between 50 and 60 years of age whereas osteosarcoma occurs
between 20 and 30 years of age
Most common locations are the pelvis, proximal femur and shoulder girdle, whereas osteosarcoma occurs
most often around the knee
When chondrosarcoma occurs in the pelvis, it is often large, high grade, diagnosed late, and has a poor
prognosis
Secondary
Secondary form occurs in about 25% of cases
Malignant transformation from preexisting enchondroma or osteochondroma Variants of chondrosarcoma: (based on histology and location)
Clear cell (intermediate grade) extraosseous
Atypical enchondroma (juxtacortical chondroma)
Clinical Presentation
Persistent, dull, aching pain
Found in an older age group peaking at 45 years of age
Majority of chondrosarcomas occur about the hip and pelvis
Radiographic
Subtle, radiolucent, permeative lesion
May have hazy or speckled calcifications with either a diffuse salt and pepperpattern or a more discrete
popcorn pattern
Pattern of calcification is usually diagnostic of cartilaginous tumor
Treatment
Tumor does not respond to x-ray therapy nor to currently available antineoplastic drugs
Low grade tumors:
Rarely metastasize
Rarely recurs after wide limb salvaging excision
The involved bone is resected along with a small cuff of surrounding muscle
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High grade tumors
Have higher rate of recurrence after limb salvage (requires amputation)
Are prone to pulmonary metastases
Osteosarcoma
Malignant tumor of bone in which neoplastic osteoid is produced by a proliferating spindle cell stroma
Most common primary malignant bone tumor of mesenchymal derivation
Arises in adolescents and affects males slightly more often than females
Locations
Occurs in region of knee (distal femur or proximal tibia) in 50% of patients
Other sites include proximal humerus, proximal femur, and pelvis
Most osteosarcomas occur in the metaphysis
Infrequently occurs in the spine
Clinical Presentation
Initial symptom is a painful bony mass
Significant number of osteosarcomas in adults occur in association with Pagets disease
PrognosisAt time of diagnosis, most osteosarcomas are Stage 2b lesions that have infiltrated the soft tissue in 50% of
adolescent patients; the tumor penetrates growth plate into epiphysis
Metastasis
Osteosarcoma tends to have early hematogenous metastasis
Pulmonary or lymph node metastases are detected at presentation in about 10% of patients
Pulmonary metastases are usually detected within and year after diagnosis
Undetectable micrometastases are probably present in lungs of most patients at time they first seek
medical attention
Without control of micrometastatic disease, there will be x-ray evidence of lung metastases in up to 80%
of patients after 1-2 years; following surgical resection, skip metastases are found in 25% of patients.
Survival
In the past survival rate was around 15%, but with adjunctive therapy survival is greater than 50%.
Metastatic disease evident at presentation also indicates presence of more aggressive disease and poor
prognosis
Treatment
Surgery alone as a treatment yields only a 20% survival rate; with adjuvant chemotherapy, the 5 year
survival rate is > 50%
Some surgeons insist on preoperative chemotherapy in the management of osteosarcoma
Commonly used agents include doxorubicin, cisplatin, high-dose methotrexate, ifosfamide, and cy-
clophosphamide
Limb Salvage versus Amputation
Limb salvage surgery does not seem to have a higher local recurrence rate than amputation.
Surgical resection of osteosarcoma pulmonary metastases
Aggressive surgical resection will improve 5-year survival rate.
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2.5 Osteomyelitis
Initially we see soft tissue swelling with obliteration of fascial planes. Bony changes appear on x-ray in 10-14
days. Initial changes include decreased bone density or localized osteoporosis. Periosteal reaction with absence of
Sharpys fibers is noted. Indistinct changes in bony appearance can occur such as a break in the cortex and a lack of
bony definition.
Sequestra involucrum and cloaca are relatively late changes seen in osteomyelitis. Sequestra is dead avascularbone that the body tries to wall off. Initially sequestra appears as the same density as normal bone. Due to hyper-
emia, the surrounding live viable bone will become diminished in density and the sequestra will appear relatively
more dense. If involucrum (granulation tissue) is lied down over the sequestra, we will see an absolute increase in
bone density. Involucrum is granulation tissue that appears radiolucent. As it consolidates and ossifies, it takes on
the density of bone.
Cloaca is a hole in the bone caused by proteolytic enzymes and pressure. It is more commonly seen in
hematogenous OM than direct extension osteomyelitis.
Diagnosing OM
It takes 10-14 days for osteomyelitis to show up on x-ray. A technesium bone scan becomes positive for
osteomyelitis 24-48 hours after symptoms appear.A triphasic technesium scan is useful in differentiating an acute cellulitis from acute OM. The three phases are
the blood flow, blood pooling, and the delayed. The first two stages measure blood, the third stage measures osteo-
genesis. Acute cellulitis is hot in the first two stages and cool in the third stage. Acute OM is hot in all three stages,
getting hotter in the third stage.
Gallium, a soft tissue-scanning agent is often used in conjunction with a technesium scan. Gallium binds with
the ferroproteins in white blood cells. It is better for chronic infections because it stays hot for a long time. Focal gal-
lium uptake in bone is characteristic of OM.
Indium is a soft tissue-scanning agent that is better for acute infections. Indium does not localize to bone well.
The most sensitive nuclear medicine scan for osteomyelitis is a technesium labeled lymphocyte scan. Uptake in
bone is highly suggestive for OM.
The most reliable magnetic resonance study is a fat suppression (STIR), gadolinium-enhanced scan. Increasedsignal intensity in bone is highly suggestive of OM.
2.6 Rheumatology
Osteoarthritis
Osteoarthritis is an insidious disease related to aging, although not all old people get it. It is associated with
weight-bearing joints but is common in the shoulder.
It is primarily a disease of the cartilage, which becomes soft and frayed. The primary radiographic changes are
hypertrophic.
Initially we see non-uniform joint space narrowing. There is subchondral sclerosis. Abnormal pressure in the
joint results in subchondral cyst formation, which does not erode the cortex. Abnormal forces at the joint cause the
capsule and ligaments to pull forming osteophytes and exostoses.
Because OA is not an inflammatory arthritity, osteoporosis is not a primary part of the disease. However, if the
patient stops ambulating because of the pain, disuse osteoporosis can occur. Joint fusions are not a primary part of
the disease, although exostosis can impinge and inhibit range of motion.
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Rheumatoid Arthritis
Rheumatoid is a T-cell mediated collagen vascular disease, which affects joints. Although the full-blown disease
is bilaterally symmetrica1, the initial onset can be unilateral. There is a predilection for young women 3:1 over
young men.
Rheumatoid is primarily an atrophic arthritity. There appears to be a predilection for the metatarsals before it
affects the phalanges. Fusiform swelling of the digits is common.Initially effusion of the joints is noted giving uniform joint space widening. Periarticular osteoporosis is a com-
mon early radiographic feature. Uniform joint space narrowing due to consolidation of panus is a relatively late
finding.
Joint fusions are uncommon but possible. Periarticular erosions in the area of the synovium are common.
Subluxations and dislocations are possible with fibula deviations. Subchondral cysts, which can erode through the
cortex, are present.
Seronegative Arthritis
Ankylosing Spondylitis
Ankylosing Spondylitis primarily affects the sacroiliac joints and the spine. The peripheral joints may also be
involved. A high incidence of the HLA-B27 antigen is present. There is a predilection for young males 3:1 overfemales.
Back pain is usually the first clinical manifestation. Bilateral sacroiliitis is common. Complete bony ankylosis is
possible. Syndesmophyte formation can occur. Fusion of the vertebral column resulting in bamboo spine is an end
result.
Bony erosions at tendon insertions and synovium are possible, as in the other seronegative arthritities.
Psoriatic Arthritis
In 10% of the cases the arthritic lesions precede the skin lesions. A diagnosis of psoriatic arthritis cannot defini-
tively be made without the skin lesions. There is an increased incidence of the HLA-B27 antigen in psoriatic arthritic
patients.
Entheseopathy is common especially of the tendoachilles and plantar fascia. In two-thirds of the patients mono
or oligoarticular arthritis is present similar to that seen in the other sero negative arthritities. In one-third to one-half of the patients, the disease will evolve into a symmetrical distribution similar to that of rheumatoid.
Psoriatic arthritis characteristically has both atrophic and hypertrophic changes with a lack of osteoporosis.
Pauciarticular erosions are present. Joint space widening with well-demarcated articular borders are characteristic.
There are intraarticular erosions. Joint fusions are common.
Saucer-in-cup or pencil-in-cup deformities are associated with psoriatic arthritis but occur less than 3% of the
time. Hypertrophic changes of the base of one phalanx with atrophic changes of the head of the adjoining phalanx
give this appearance.
There is a predilection for the interphalangeal joints with lack of fibula deviation. There is no significant
osteoporosis.
Reiters Reactive Arthritis
There is a marked increase in the presence of the HLA-B27 antigen. Young men have the highest incidence ofthe disease. The classic triad of symptoms is non-gonococcal urethritis, conjunctivitis, and arthritis. Keratoderma
blennorrhagicum, a dermatological lesion of the palms and soles, can also occur.
Dactylitis, or sausage-like soft tissue swelling of the digits, occurs. The lower extremity is affected more than the
upper. Periarticular osteoporosis with intraarticular erosions are present. Erosions are also present at synovial and
tendinous insertions.
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Gout
Gout is the symptomatic deposition of uric acid crystals in the joint. It has its highest incidence in older males.
Females with gout are usually post-menopausal.
Gout has a predilection for the smaller joints with the highest incidence at the first metatarsal phalangeal joint.
It takes many years and multiple attacks for gouty erosions to show up on x-ray. The classic lesion is an erosion
with overhanging cortical margin (Martels Sign) with a rat bite-like appearance. Martels Sign appears less than
10% of the time.
Urate tophi may calcify, giving it a cloudy amorphous appearance in the soft tissue.
Pseudogout (Calcium Pyrophosphate Dihydrate Deposition)
Pseudogout is the symptomatic deposition of calcium pyrophosphate dihydrate crystals. Pseudogout has a
predilection for the knee and other large joints.
The classic radiographic appearance is calcification in articular cartilage, as well as in articular capsule liga-
ments and tendons.
2.7 Osteochondrosis
An osteochondrosis is an aseptic necrosis-like process at a growth center (epiphysis or apophysis). A true osteo-
chondrosis will undergo a sequence of events characteristic of an infarct. Initially there will be an infarct followed byreabsorption, revascularization, and remodeling. All true osteochondrosis undergo this sequence of events and show
characteristic radiographic changes.
An early diagnostic sign in a true osteochondritity is a crescent sign. This is a crescent or triangular shape radio-
density in the subchondral bone that is an early indicator of infarct.
Immobilization is required to prevent joint destruction and allow healing with minimal sequela. Sequela result
in joint flattening, neck broadening, and degenerative joint disease.
True Osteochondrosis
Legg-Calve-Perthes Disease
This is an osteochondrosis of the proximal femoral epiphysis. It is more common in males than females with a
peak incidence of about 5 yrs of age.
Freibergs DiseaseThis is an osteochondrosis of the metatarsal head seen in young females between the age of 10 and 15 yrs of
age. It is most common in the second metatarsal bead. Studies show this is likely a stress fracture of the epiphy-
seal plate. This results in a flattening of the metatarsal head with an S-shaped joint and degenerative joint
disease.
Osteochondrosis of the Sesamoids
Radiographically, we see cystic erosions in the sesamoids.
Abnormalities in Osteogenesis and Chondrogenesis
Osgood Schlatters Disease (Osteochondrosis of the Tibial Tuberosity)
This is a tendonitis of the patella tendon with bone formation in the tendon. A normal tibial tubercle may be
fragmented and teardrop-shaped. This is not an x-ray diagnosis. This is most commonly seen in young boys with
pain on palpation of the tibial tuberosity. There is pain upon squatting and going up and down steps.
Blounts Disease (Osteochondrosis of the Medial Tibial Condyle)
This is an abnormality of chondrogenesis of the proximal medial tibial epiphysis. This is most likely seen in
young black males. The infantile form of the disease is much more severe than the juvenile. Significant tibial bowing
may result.
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Anatomical Variants
Kohlers Disease
This is associated with delayed ossification of the navicular. We see a disk-shaped navicular narrowed in its
A/P diameter. It may be fragmented, sclerotic, hazy, and out of focus. It will eventually ossify normally.
There is no real pathology.
Islins Disease
This is a normally fragmented or multi-partite apophysis at the base of the fifth metatarsal.
Severs Disease
The calcaneal apophysis is the most sclerotic apophysis in the body. Irregularity, fragmentation, and new
bone formation is normal. There are no reported cases of long-term deformity associated with this disor-
der. The three most common etiologies of heel pain in children are plantar fasciitis, Achilles tendonitis, and
Haglund's deformity. The heel pain is not caused by the fragmented calcaneus but usually by one of these
pathologies.
Osteochondritis Dissecans
This is a localized ischemic necrosis that occurs more frequently in young men and boys often following
injury. It is an osteochondral fracture that results in a button of necrotic bone separating from the joint
surface. It is seen most commonly in the knee.