Musculoskeletal MRI: A Computer-Based Case Review

1
Musculoskeletal MRI A Computer-Based Case Review

• Christopher Wedding, M.D., Daniel Zee, M.D.
• Patrick M. Colletti, M.D.
• Department of Radiology, Keck USC School of
  Medicine, Los Angeles, CA

2
Case 1History23 year old with painand
swelling in left knee
3
Serial Sagittal PD
4
Serial Coronal PD
5
Serial Fat Saturation Sagittal PD
6
Coronal Fat Saturation PD, post-contrast
7
Findings
8
Findings

• Coronal and Sagittal PD MR images show lobulated
  heterogeneous soft tissue mass about the knee
  joint, with areas of intermediate-to-low signal
  intensity and areas of osseous erosions
• Sagittal FS PD show similar findings
• Coronal FS PD with contrast shows heterogeneous
  avid enhancement, with persistent areas of low
  signal intensity

9
Coronal and Sagittal PD MR images show
lobulated heterogeneous soft tissue mass
about the knee joint, with areas of
intermediate-to-low signal intensity
10
Sagittal FS PD show findings similar to the
PD MR images, with a lobulated,
heterogeneous mass with areas of low signal
intensity
Coronal FS PD with contrast shows
heterogeneous avid enhancement, with
persistent areas of low signal
intensity
11
Diagnosis Pigmented Villonodular Synovitis
(PVNS)
12
Pigmented Villonodular Synovitis (PVNS)

• Typically presents in third or fourth decade
• Intermittent pain and swelling, with decreased
  range of motion
• Approx. 80 of cases affect the knee other large
  joints affected in decreasing order of freq.
  include the hip, ankle, shoulder, and elbow
• Often an assoc joint effusion w/ serosanguinous
  or xanthochromic fluid

• Grossly, the lesion has appearance of shaggy red
  beard because of frondlike synovial projections
  containing hemosiderin (imparting red color)
• Surgery is preferred treatment, but recurrence
  rates are high (near 50)
• Malignant transformation is exceedingly rare

13
Pigmented Villonodular Synovitis (PVNS)

• Radiographs may demonstrate a noncalcified soft
  tissue mass, joint effusion, or erosive changes
  (with well-defined thinly sclerotic margins)
• Joint space and bone density typically preserved
• Radiographs may be normal

• MRI appearance is often characteristic, with
  heterogeneous synovial mass, low-intermediate
  signal intensity on T1-weighted images, with
  similar signal characteristics on T2-weighted
  images (due to hemosiderin)

14
Pigmented Villonodular Synovitis (PVNS)

• The differential diagnosis for low signal
  intensity lesions on T1 and T2 in and around the
  joint
• PVNS
• Gout (low signal due to fibrous tissue,
  hemosiderin, or calcification)
• Primary or secondary amyloidosis
• Fibrous lesions
• Disorders causing hemosiderin deposition (e.g.
  hemophilia, synovial hemangioma, neuropathic
  osteoarthropathy)

15
Case 2 History47 year old female withpain
and locking in knee
16
Serial Sagittal PD
17
Serial Coronal PD
18
Findings
19
Findings

• Sagittal PD MR images demonstrate an abnormal
  low signal intensity structure anterior to the
  posterior cruciate ligament, producing a
  double PCL sign
• Coronal PD MR images demonstrate show this same
  abnormal low signal intensity structure in the
  intercondylar notch, inferior to the PCL
• This low intensity structure represents a
  displaced meniscal fragment from a torn meniscus

20
Displaced fragment lying inferior to PCL in
intercondylar notch
Double PCL sign, with displaced meniscal
fragment lying anterior to normal PCL
21
Diagnosis Bucket-Handle Tear ofMedial
Meniscus withDouble PCL Sign
22
Meniscal Tears

• The menisci are important in load bearing and
  knee function up to 50 of load bearing is
  transmitted in extension and 85 in flexion
• Tears in the menisci may result from acute trauma
  or repetitive trauma
• Medial meniscus is injured more commonly than
  lateral

• Acute tears are usually due to athletic injuries
  with crushing of the meniscus between the tibia
  and femoral condyles
• Patients present with knee pain locking, which
  is usually related to bucket-handle tear or
  giving way, which is often related to pain
  frequently complain of pop or clunk with
  motion

23
Bucket-Handle Meniscal Tears

• A bucket-handle tear consists of a longitudinal
  tear of the meniscus, running parallel to the
  main axis of the meniscus, with displacement of
  the inner fragment

• The term "bucket-handle tear" relates to its
  appearance, in which the inner, displaced
  meniscal fragment resembles a handle and the
  peripheral, nondisplaced part resembles a bucket

24
Bucket-Handle Meniscal Tears

• Several signs are associated with bucket-handle
  tears
• Absent bowtie sign when fewer than two bowtie
  segments of the meniscus are present on
  sequential sagittal MR images
• Flipped meniscus sign displaced fragment lies
  directly on anterior horn, producing an
  abnormally tall (gt6 mm) anterior horn

• Double PCL sign when the displaced meniscal
  fragment lies below the PCL, giving the
  appearance of two ligaments
• Loose bodies or fragments of menisci in the
  intercondylar notch may also be seen

25
Pitfalls in Meniscal Imaging

• May only see one bowtie in children or small
  adults (should be bilateral) post-operative knee
  (with debridement of free edge) older adults and
  severe osteoarthritis (with thinning of meniscus
  due to wear of free edge)
• Transverse ligament in anterior aspect of knee
  in Hoffas fat pad connects anterior horns of
  medial and lateral menisci may be mistaken for
  tear of anterior horn
• Meniscofemoral ligament originates on medial
  femoral condyle, runs obliquely across knee in
  intercondylar notch runs anterior (ligament of
  Humphry) or posterior (ligament of Wrisberg) to
  the PCL, and inserts into the posterior horn of
  the lateral meniscus

26
Pitfalls in Meniscal Imaging

• Popliteus tendon pseudotear originates on the
  lateral femoral condyle and extends inferiorly
  between the posterior horn of the lateral
  meniscus and the joint capsule it runs
  obliquely and extends posterior to join the
  muscle belly, which lies just posterior to the
  proximal tibia can mimic a tear of posterior
  horn of lateral meniscus
• Speckled anterior horn of lateral meniscus
  caused by fibers of ACL inserting into meniscus,
  giving a speckled appearance, can resemble a
  macerated or torn anterior horn

27
Case 3History29 year old male with left knee
pain, s/p trauma
28
Serial Sagittal PD
29
Serial Sagittal Fat Saturation PD
30
Serial Coronal T1
31
Findings
32
Findings

• Sagittal PD MR images demonstrate intermediate
  signal in the posterior cruciate ligament
  (instead of the normal low signal)
• Additionally, on sagittal PD, there is a
  curvilinear band of very low signal at the site
  of the PCL attachment to the tibia, displaced
  from the tibia
• Sagittal fat saturation PD also demonstrates the
  aforementioned findings, along with a large
  knee effusion
• Coronal T1 images demonstrate a defect in the
  cortical margin of the proximal tibia

33
Sagittal PD MR images demonstrate abnormally
increased signal intensity in the posterior
cruciate ligament
Additionally, there is a curvilinear band of low
signal at the site of the PCL attachment to the
proximal tibia this low signal approximates
that of cortical bone
34
Sag FS PD MR images show findings similar to
the Sag PD, with increased signal in the PCL,
an abnormal low density structure
representing avulsed cortical bone, and a
large effusion
Suprapatellar effusion
Torn PCL
Avulsed fragment
Coronal T1 images demonstrate a defect in the
proximal tibia, at the site of attachment of
the PCL
35
Diagnosis Posterior Cruciate Ligament
Tear(with avulsion fracture)
36
Posterior Cruciate Ligament Tear

• The PCL arises from the posterior part of the
  intercondylar area of the tibia, passes
  superiorly and anteriorly on the medial side of
  the ACL to attach to the anterior part of the
  lateral surface of the medial condyle of the femur

• The PCL tightens during flexion of the knee
  joint, preventing anterior displacement of the
  femur on the tibia or posterior displacement of
  the tibia on the femur
• It also helps prevent hyperflexion of the knee
  joint
• In the weight-bearing, flexed knee, the PCL
  stabilizes the femur (e.g. when walking downhill)

37
Posterior Cruciate Ligament Tear

• PCL tears are less common than ACL tears
• Mechanism of injury usually direct blow to
  anterior aspect of knee while the knee is in
  flexion, e.g. a car accident in which the knee
  strikes the dashboard, striking just below
  patella, forcing tibia posteriorly, tearing the
  PCL

• Because of the force mechanism required to
  rupture the PCL, isolated complete PCL tears are
  not common these tears occur more frequently in
  combination with injuries to other ligaments of
  the knee

38
Posterior Cruciate Ligament Tear

• The normal PCL is a gently curved, homogeneously
  low signal structure
• When the PCL tears, it typically does not have an
  actual disruption of the fibers, but instead
  stretches and is no longer structurally competent

• On PD or T1, the PCL takes on uniform diffuse
  intermediate signal intensity and is thicker than
  normal
• The torn PCL does not exhibit high signal on
  T2WI, although some reports demonstrate high
  signal on STIR

39
Another example ofPCL tear33 year old male
with right knee pain, s/p motorvehicle accident
40
Serial Sagittal PD
41
Serial Sagittal PD with Fat Saturation
42
Sagittal FS PD MR images demonstrate increased
marrow signal in the proximal tibia, secondary
to mechanism of injury (knee-to-dashboard
injury)
Note the large, high signal intensity
knee effusion
Sagittal PD MR images demonstrate intermediate
signal in the posterior cruciate ligament,
consistent with tear
43
Case 4History55 year old male withright knee
pain
44
Serial Coronal T1
45
Serial Sagittal Fat Saturation PD
46
Findings
47
Findings

• Coronal T1 MR images demonstrate a discrete area
  of subchondral decreased signal intensity
  involving the weight bearing portion of the
  medial femoral condyle
• Sagittal FS PD MR images demonstrate diffuse
  increased signal intensity within subchondral
  bone and a high signal intensity joint effusion

48
Coronal T1WI demonstrates an area of
subchondral decreased signal intensity
involving the weight bearing portion of the
medial femoral condyle
Sagittal FS PD demonstrates increased
subchondral marrow signal intensity in the
medial femoral condyle and a high signal
intensity knee effusion
49
Diagnosis Spontaneous Osteonecrosis of the
Knee (SONK)
50
Spontaneous Osteonecrosis of the Knee (SONK)

• As the name implies, this clinical entity is
  defined as necrosis of the weight bearing portion
  of the femur or tibia with associated subchondral
  fracture and collapse
• Typically occurs in ages 50 and older, more
  common in females
• Intense pain often after trivial trauma

• Weight-bearing portion of medial femoral condyle
  most commonly affected, but lateral femoral
  condyle can also be affected
• Pain may resolve spontaneously alternatively,
  larger lesions may progress to secondary
  degenerative disease

51
Stage Radiographs MRI
1 Normal Geographic area of increased intensity on T2WI decr. intensity T1WI
2 Slight flattening of the femoral condyle, sclerosis of subchondral tibial bone Geographic area with surrounding low intensity on T1WI
3 Subchondral lucency with surrounding sclerosis Subchondral area of reduced to normal signal intensity
4 Same as above, but wider area of sclerosis Surrounded by low intensity area on both T1 and T2
5 Above changes plus degenerative joint disease Geographic area of low intensity with joint space narrowing

• From Lotke PA, Ecker ML. Current Concepts Review.
  Osteonecrosis of the knee. J Bone Joint Surg
  1988 70 470-473.

52
Case 5History10 year old female with knee
pain
53
Serial Coronal PD
54
Sagittal PD
55
Serial Sagittal Fat Saturation PD
56
Findings
57
Findings

• Coronal and Sagittal PD demonstrate a
  subchondral area of decreased signal intensity
  involving both the posterior aspect of the
  lateral femoral condyle and the lateral aspect
  of the medial femoral condyle
• Sagittal PD also demonstrates an in situ
  osteochondral body in the medial femoral
  condyle
• Sagittal FS PD MR images demonstrate increased
  subchondral signal intensity

58
Note the open femoral and tibial physes on these
images
In situ osteochondral body in the medial
femoral condyle

• Coronal and sagittal PD images
• demonstrate a subchondral
• area of decreased signal
• intensity involving both
• the posterior aspect of the
• lateral femoral condyle and
• the lateral aspect of the
• medial femoral condyle

59
Sagittal FS PD MR images demonstrate increased
subchondral signal intensity
60
Diagnosis Osteochondritis Dessicans
61
Osteochondritis Dessicans

• Detachment of fragment of articular cartilage,
  often with an attached fragment of subchondral
  bone
• Typically affects teenagers, with average age of
  onset at 15 years
• Symptoms include pain or instability
• Etiology unclear, probably related to repetitive
  trauma and/or ischemia

• Most commonly affects lateral aspect of medial
  femoral condyle (75), medial aspect of medial
  femoral condyle (10), and lateral aspect of
  lateral condyle (15)
• Right knee is involved slightly more often than
  the left, but bilateral involvement occurs in up
  to 25 of cases

62
Osteochondritis Dessicans
Grade MR Features
1 Cartilage intact with normal thickness, with abnormal signal (in bone and cartilage)
2 Linear breach of articular cartilage
3 Abnl. signal intensity around fragment (incr. on T2WI, decr. on T1WI)
4 Mixed or low signal intensity with fragment in place or loose in joint
63
Osteochondritis Dessicans vs. Spontaneous
Osteonecrosis of the Knee
SONK OCD
Demographics Age 50, females more likely Teens, males outnumber females 31
Most common location Wt-bearing portion medial fem. condyle Lateral aspect medial femoral condyle
Clinical presentation Acute onset of pain after minor trauma Insidious onset of pain, antecedent trauma in up to 50
64
Case 6 History23 year old female with lump
along left chest wall
65
Serial Coronal T1 FSE, with marker over palpable
abnormality
66
Serial Axial STIR
67
Serial Axial T1
68
Serial Axial T1 Fat-Saturation Post-Contrast
69
Findings
70
Findings

• Coronal and axial T1WI demonstrate a large,
  well- circumscribed complex mass, with
  predominantly high signal intensity, with
  septations and areas of lower signal
• Axial STIR show the mass to be mostly low in
  signal intensity (following signal
  characteristics of fat), with areas of high
  signal corresponding the low signal areas on T1
• The portion of this mass that is low on T1 and
  high on STIR shows enhancement with gadolinium

71
Coronal and axial T1WI demonstrate a large,
well-circumscribed complex mass, mostly
high on T1 (like the adjacent subcutaneous
fat), with septae and areas of lower signal
Note the septations and lower signal areas of
the mass
72
On axial STIR, the mass is predominantly low
(like the adjacent fat), with an area of
abnormal high signal intensity in the
anteromedial portion of the mass
On FS T1WI Post-Gd, there is contrast
enhancement in this portion of the mass
73
Diagnosis Liposarcoma of chest wall
74
Liposarcoma

• The second most common soft tissue sarcoma in
  adults (most common is malignant fibrous
  histiocytoma)
• Five histologic subtypes
• 1) Well-differentiated subtype (54) considered
  a low- grade malignancy
• 2) Myxoid (23) intermediate-grade
• 3) Round cell (5) high-grade
• 4) Pleomorphic (7) high-grade
• 5) Dedifferentiated (10) high-grade
• Dedifferentiated liposarcomas are more common in
  the retroperitoneum the other subtypes are more
  common in the extremities

75
Liposarcoma Well-Differentiated Subtype

• MRI of well-differentiated liposarcoma a
  predominantly fatty mass with irregularly
  thickened linear or nodular septa, decreased
  signal intensity on T1WI and increased on T2WI
• There is significant overlap of imaging
  appearances of well-differentiated liposarcoma
  and lipoma variants, often rendering distinction
  between the two impossible

76
Liposarcoma Dedifferentiated Subtype

• A dedifferentiated sarcoma is one in which a
  borderline or low-grade neoplasm is associated
  with a high-grade histologically distinct
  neoplasm, e.g., a well-differentiated liposarcoma
  juxtaposed with a high-grade sarcoma, such as
  malignant fibrous histiocytoma or fibrosarcoma
• Usually retroperitoneal
• Imaging characteristics follow above definition,
  with a well-defined nonlipomatous mass adjacent
  to a predominantly fatty tumor

77
Liposarcoma Other Subtypes

• Myxoid, pleomorphic, and round cell subtypes
  often do not contain significant amounts of fat,
  and only 50 will demonstrate fat with imaging
• Pleomorphic and round cell types are more
  heterogeneous, while myxoid liposarcoma is more
  homogeneous

78
Case 7 History40 year old alcoholic
male,with severely limitedrange of motion of
shoulder
79
Serial Axial T1
80
Serial Axial FIR
81
Findings
82
Findings

• Axial T1WI demonstrate posterior dislocation of
  the humeral head with associated compression
  fracture of the anteromedial humeral head, with
  impaction on the posterior glenoid rim
• Axial STIR images demonstrate the aforementioned
  findings, as well as increased marrow signal
  intensity consistent with edema

83
These axial T1WI demonstrate posterior
dislocation of the humeral head
Note the compression fracture of the anteromedial
humeral head, producing an MR trough sign
84
Axial STIR images demonstrate increased marrow
signal intensity consistent with edema
85
Diagnosis Posterior Shoulder Dislocation
86
Posterior Shoulder Dislocation

• Posterior shoulder dislocation accounts for only
  2-4 of glenohumeral joint dislocation
• Anterior (subcoracoid) shoulder dislocation
  accounts for approximately 96 of glenohumeral
  joint dislocation

• Causes of posterior dislocation include
  traumatic, especially in convulsive disorders or
  electroconvulsive therapy
• Usually due to axial loading of an adducted and
  internally rotated arm
• Often unrecognized initially and misdiagnosed as
  frozen shoulder

87
Posterior Shoulder Dislocation Imaging Signs

• Rim Sign increase space between anterior rim
  of glenoid and medial border of humeral head
  (since the dislocated humeral head rests against
  the posterior glenoid rim, the space between the
  anterior rim and humeral head appears increased
• Lightbulb Sign humeral head is fixed in
  internal rotation no matter how forearm is
  turned
• Trough Sign compression fracture of
  anteromedial humeral head, due to impaction on
  posterior glenoid rim, sometimes referred to as
  reverse Hill-Sachs deformity

88
Posterior Shoulder Dislocation Imaging Signs

• Half-Moon Sign Normally the medial head of
  humerus overlaps the glenoid to form a shadow
  shaped like a half-moon, which reaches down to
  the inferior border of the glenoid fossa, ABSENT
  in posterior dislocation.
• Isolated avulsion fractures of the lesser
  tuberosity should raise suspicion of an
  associated posterior dislocation
• Typically, a trans-scapular Y view or
  transthoracic lateral radiograph of the humeral
  head best demonstrate a posterior dislocation

89
Case 8 History57 year old female withleft
shoulder pain andreduced range of motion
90
Coronal Oblique PD
91
Coronal Oblique STIR
92
Findings
93
Findings

• Coronal PD images demonstrate multiple, lobulated
  masses within the glenohumeral joint, with
  intermediate-to-low signal intensity
• Coronal STIR images demonstrate lobulated areas
  of high signal within the joint, likely due to
  joint effusion and/or synovial thickening

94
Coronal PD images demonstrate multiple,
lobulated masses within the glenohumeral
joint, with intermediate-to-low
signal intensity
Coronal STIR images demonstrate lobulated
areas of high signal within the shoulder
joint
95
Diagnosis Synovial Osteochondromatosis
96
Synovial Osteochondromatosis

• Characterized by synovial metaplasia,
  hyperplasia, and hyaline or myxoid change
• The synovial lining undergoes nodular
  proliferation, and fragments may break off from
  the synovial surface to lie free within the joint
• Within the joint, these loose bodies are
  nourished by synovial fluid and may grow,
  calcify, or ossify

• Malesgtfemales 2-4 fold
• All ages can be affected, but often diagnosed in
  ages 20-50 years
• Typically monoarticular, affecting the large
  joints, including the knee, hip, elbow, and
  shoulder however, the process may affect any
  synovial surface, including the extra-articular
  bursa

97
Synovial Osteochondromatosis

• Patients typically present with a history of
  several years of joint pain with swelling, with
  limited range of motion and/or a history of
  locking
• The natural history of the disease includes
  gradual progression of disease, joint
  deterioration, and secondary osteoarthritis

98
Synovial Osteochondromatosis

• Radiographs frequently demonstrate characteristic
  features, including multiple calcified or osseous
  bodies within the joint or bursa
• Pressure erosions and subchondral erosions may be
  seen in the adjacent bone

• MRI with T1WI and PDWI demonstrates multiple
  rounded bodies that are isointense or hypointense
  to muscle, may exhibit signal characteristics
  similar to that of cortical bone
• T2WI may show areas of high signal due to joint
  effusion and synovial thickening
• Hallmark is calcification in synovium, which is
  seen as signal void in synovium

99
Case 9 History55 year old female withmass
behind the knee
100
Serial Sagittal PD
101
Serial Sagittal Fat Saturation PD
102
Serial Axial Fat Saturation PD
103
Findings
104
Findings

• Sagittal PD images demonstrate an intermediate
  signal intensity ovoid or fusiform soft tissue
  mass, with a peripheral rim of fat (split-fat
  sign)
• Sagittal FS PD images demonstrate a predominantly
  high signal intensity ovoid or fusiform soft
  tissue mass, with central low signal, with an
  associated entering nerve
• Axial FS PD images demonstrate predominantly
  high signal intensity ovoid soft tissue mass,
  with central low signal, giving a target sign

105
Sagittal PD images demonstrate an intermediate
signal intensity fusiform soft tissue mass, with
a peripheral rim of fat (split-fat sign)
Sagittal FS PD images demonstrate a
heterogeneously hyperintense soft tissue
mass, with eccentric entering nerve
106
Axial FS PD images demonstrate a predominantly
high signal intensity ovoid soft tissue mass,
with central low signal, producing a target
sign
107
Diagnosis Schwannoma
108
Schwannoma (Neurilemmoma)

• Along with neurofibroma, this is a type of benign
  peripheral nerve sheath tumor (BPNST)
• A benign encapsulated tumor of the nerve sheath,
  the cell of origin thought to be Schwann cell
• Presents with a cosmetic deformity, palpable
  mass, or secondary (compressive) neurologic
  symptoms

• Most commonly affects cutaneous nerves of head
  and neck, flexor surfaces of extremities,
  posterior mediastinum, and retroperitoneum
• The mass is usually mobile in the transverse
  plane and tethered along the axis of the nerve
  from which it arises

109
Schwannoma (Neurilemmoma)

• MRI appearance
• T1WI soft tissue mass isointense to muscle
• T2WI hyperintense soft tissue mass, with center
  of low signal (due to collagen and condensed
  schwann cells), resulting in target sign
• Displaced peripheral rim of fat, split fat sign
• May see entering and/or exiting nerve root,
  eccentric to mass
• Variable contrast enhancement, often peripheral
  enhancement

110
Case 10History 55 year old male with
shoulder pain
111
Serial Coronal Oblique T1
112
Serial Coronal Oblique STIR
113
Serial Axial Fat Saturation PD
114
Serial Coronal Oblique T1
115
Findings
116
Findings

• Coronal oblique T1 demonstrates fat signal within
  the supraspinatous muscle consistent with
  atrophy. The musculotendinous junction of the
  supraspinatous is retracted medially. The second
  set of T1 images show medial displacement of the
  biceps tendon. Acromioclavicular joint
  degenerative changes are present.
• Coronal STIR images demonstrate decreased
  distance between the humerus and the acromion and
  high signal in the distal supraspinatous tendon
• Axial FS PD images reveal an empty bicipital
  groove, confirming the findings seen on the
  coronal images. The dislocated biceps tendon is
  an ovoid hypointensity medial to the humeral head
  in the anterior aspect of the glenohumeral joint.
  The subscapularis tendon has abnormal signal and
  is also torn.

117
Coronal oblique T1 demonstrates fat
signal within the supraspinatous muscle,
consistent with atrophy
118
Coronal oblique STIR shows high signal in
the distal supraspinatous tendon
Decreased acromiohumeral distance
119
Axial FS PD images show that the bicipital
groove is empty
The biceps tendon has dislocated medially to the
anterior aspect of the glenohumeral joint
Torn subscapularis tendon
120
The biceps tendon is dislocated medially
121
Diagnosis Complete supraspinatus tendon tear
with long head of bicepstendon dislocation
122
Supraspinatus tear

• The typical clinical presentation is pain,
  weakness and decreased range of motion following
  overuse (microtrauma). Less commonly, a single
  traumatic event may lead to a tear.
• Supraspinatus tears are often a consequence of
  the shoulder impingement syndrome, but not
  always.

• The supraspinatus is the most frequently torn
  rotator cuff tendon.
• Supraspinatus tears may be classified as partial
  (joint surface), partial (bursal surface), or
  complete.
• Atrophy (fatty infiltration) of the supraspinatus
  muscle is seen in patients with chronic tear (as
  in this case).

123
Complete supraspinatous tear Imaging

• Conventional MRI without arthography reveals an
  interruption of the tendon with fluid signal
  intensity within the defect.
• In arthography, contrast is present in the
  shoulder joint and in the subacromial-subdeltoid
  bursa. The contrast reaches this bursa through
  the defect of the torn segment.
• Tears tend to be located within 1 cm of the
  insertion on the greater tuberosity.
• If arthrography is not performed, secondary signs
  may be useful in making the diagnosis on MR
  retraction of the musculotendinous junction,
  thinning/irregularity of the tendon, fluid in the
  subacromial-subdeltoid bursa.

124
Long head of biceps tendon dislocation

• Usually results from acute trauma.
• The transverse humeral ligament holds the biceps
  tendon in place and is always disrupted when the
  biceps tendon is dislocated.
• Biceps tendon dislocations are frequently
  associated with tears of the subscapularis. When
  the biceps tendon is dislocated medially into the
  glenohumeral joint (as in this case), the
  subscapularis tendon is always disrupted.
• Disclocations are most easily visualized in the
  axial plane Look for the empty bicipital groove
  and the ovoid cross-section of the hypointense
  tendon. Often it will be medially located, either
  anterior or posterior to the subscapularis
  tendon.

125
Case 11 History25 year old male, s/pshoulder
injury
126
Serial Axial Fat Saturation PD
127
Findings
128
Findings

• Axial images demonstrate abnormal contour of the
  humeral head posterolaterally. Indentation is
  present, with disruption of the normal
  hypointense cortical bone. There is no
  glenohumeral joint dislocation at this time.
• Additionally, the anterior aspect of the inferior
  glenoid is discontinuous with the rest of the
  glenoid, consistent with fracture.

129
Fracture-indentation of the posterolateral
humeral head
Fracture of the anterior, inferior glenoid rim
130
Diagnosis Hill-Sachs deformity and Bankhart
lesion
131
Hill-Sachs deformity and Bankhart lesion

• The Hill-Sachs deformity refers to the
  fracture-indentation of the humeral head. The
  Bankhart lesion refers to a tear of the anterior
  inferior glenoid labrum (with or without
  associated fracture). In this case, a fracture
  (also called a bony Bankhart lesion) is also
  present.
• The mechanism for both of these entities is
  anterior shoulder dislocation. During anterior
  dislocation, the posterolateral aspect of the
  humeral head becomes indented as it strikes the
  anterior, inferior glenoid rim. The patient in
  this case was imaged post-reduction.
• Anterior shoulder dislocation secondary to trauma
  is one of the many possible reasons for the
  development of shoulder instability.

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Case 12 History25 year old male withfew
months of pain inleft lower extremity
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Serial Sagittal T1
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Serial Axial STIR
136
Findings
137
Findings

• Radiographs reveal a poorly defined metaphyseal
  sclerotic tumor, with associated soft tissue mass
  and osteoid matrix.
• Sagittal T1 images demonstrate a complex
  appearing soft tissue mass in the posterior
  aspect of the knee. The signal is heterogeneous
  but predominantly low. There is abnormal signal
  involving the proximal tibia with disruption of
  the posterior tibial cortex.
• Axial STIR images reveal that the mass has
  heterogeneous but mostly high signal. Cortical
  disruption of the tibia and abnormal marrow
  signal are confirmed.

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Radiographs reveal a poorly defined metaphyseal
sclerotic tumor, with associated soft tissue
mass and osteoid matrix
Osteoid matrix
These arrows mark the round soft tissue mass
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Abnormal low signal in proximal tibia
Complex soft tissue mass with heterogeneous
low-intermediate signal
Cortical disruption
Normal marrow signal in distal tibia
140
Cortical disruption
Heterogeneously high signal on STIR
sequence
141
Diagnosis High grade osteosarcoma
142
High grade osteosarcoma

• Osteosarcoma is the most common primary sarcoma
  arising in bone. It has a peak incidence in the
  second decade of life. A second smaller peak is
  seen among those older than 60. Older patients
  usually have a preexisting bone disease (e.g.
  Pagets disease).
• There are several subtypes of osteosarcoma.
  Conventional high-grade osteosarcomas are the
  most common, accounting for about 90.
• The metaphyses of long tubular bones (especially
  the distal femur, proximal tibia, and the
  proximal humerus) are the most common sites.
• Patients tend to present with pain and swelling.

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High grade osteosarcoma Imaging

• Radiographs are important in making the diagnosis
  osteosarcoma. MR findings are not specific. The
  appearance of osteosarcoma overlaps with other
  tumors. The importance of MRI is in the
  evaluation of the extent of the tumor.
• T1 weighted sequences are preferred for
  determining the extent of the tumor within the
  bone. This is because STIR images may
  overestimate the actual tumor burden due to the
  surrounding edema. On T1 sequences, tumor will
  appear as low signal intensity marrow
  replacement.
• It is important to note any extension into the
  epiphyses, skip lesions (across joints or in
  another part of the same bone), and the extent of
  the soft tissue component, if any.

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Case 13History33 year old female with knee
pain
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146
Serial Sagittal T1
147
Axial STIR
148
Findings
149
Findings

• Radiographs demonstrate a bubbly lytic, expansile
  lesion of the distal femoral metaphysis,
  eccentric, with an associated fracture.
• Sagittal T1 images show a predominantly low
  signal intensity mass involving the distal
  posterior femur.
• Axial STIR images reveal that the mass involves
  the posterior lateral femoral condyle. The signal
  intensity is high in the nondependent part of the
  lesion and low in the dependent part. There are
  several fluid-fluid levels. Some areas of the
  lesion are cystic-appearing with septations.

150
Radiographs demonstrate an eccentric, bubbly
lytic, expansile lesion of the distal
femoral metaphysis, with an associated fracture.
151
Low signal intensity mass involving the
posterior distal femur
152
Complex cystic mass with septations
involves the posterolateral distal femur
Fluid-fluid levels
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Diagnosis Aneurysmal Bone Cyst
154
Aneurysmal Bone Cyst

• Aneurysmal bone cysts (ABC) are expansile, lytic
  lesions occurring in young patients (10-30 years
  old), with a higher incidence in females.
• ABCs may present with pain, swelling, neurologic
  symptoms, or pathologic fracture.
• Although the exact etiology is not known, it is
  recognized that cysts can form as a result of
  trauma. ABCs also arise from other bone
  abnormalities, including other bone tumors. They
  often contain cyst-like collections and have
  internal septations and trabeculae which give it
  the classic soap bubble appearance on plain
  films.
• Currettage with bone graft is the most common
  method of treatment.

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Aneurysmal Bone Cyst Imaging

• On MR, the cystic spaces are usually high in
  signal intensity on T2, but may be low or
  intermediate depending on the content. A dark rim
  around the lesion is seen on both T1 and T2.
• Bleeding into the lesion may occur, accounting
  for some variability in MR signal.
• Fluid-fluid levels may or may not be seen.
  Although fluid-fluid levels were originally
  thought to be very specific for ABC, it is
  important to note that other entities, both
  benign and malignant, may also display this
  feature (telangiectatic osteosarcoma,
  chondroblastoma or unicameral bone cyst with
  hemorrhage).

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Another example ofaneurysmal bone cyst36 year
old female withacute pain in rightforearm after
trauma
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158
Serial Coronal STIR
159
Serial Axial STIR
160
Eccentric, expansile lytic lesion of mid-shaft
of right ulna, with associated fracture
161
Serial Coronal STIR
Hyperintense expansile lesion involving the
ulna, low signal septations are present.
162
Serial Axial STIR
Fluid-fluid levels
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Case 14History60 year old female withright
knee pain
164
Serial Sagittal PD
165
Serial Coronal PD
166
Findings
167
Findings

• The sagittal and coronal PD images demonstrate
  absence of normal fibers in the expected location
  of the anterior cruciate ligament. The posterior
  cruciate ligament is intact.
• Sagittal and coronal PD images also reveal an
  oblong ovoid hypointensity in the lateral aspect
  of the intercondylar notch, with no normal
  lateral meniscus identified.

168
There are no normal fibers between these arrows.
This is the expected location of the normal
ACL.
Abnormal low density structure in
intercondylar notch displaced meniscal
fragment
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Abnormal hypointensity in intercondylar notch
representing displaced lateral meniscal
fragment from bucket-handle tear
The normal ACL fibers are absent
170
Diagnosis Anterior Cruciate Ligament Tear
(with associated Bucket-HandleTear of Lateral
Meniscus)
171
Anterior Cruciate Ligament Tear

• The ACL is the most commonly injured major
  ligament of the knee
• The most common mechanism is the valgus-abduction
  clip injury which involves a lateral blow to the
  knee while it is in the flexed position. The
  second most common mechanism is the anterior
  blow-hyperextension injury.
• Coexistent injuries to the posterior cruciate
  ligament, menisci, and medial collateral
  ligaments are common.
• The diagnosis of the ACL tear is often readily
  apparent to the experienced clinician. The high
  association with other internal derangement,
  however, requires the use of advanced imaging for
  complete evaluation.

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Anterior Cruciate Ligament Tear Imaging

• MR is an accurate modality for detecting tears of
  the anterior cruciate ligament. Using T2
  weighted sequences, the normal ACL has a striated
  appearance with fibers running parallel to the
  roof of the intercondylar notch. If just a few
  normal fibers are seen, a torn ACL is unlikely.
  In complete disruption of the ACL, no normal
  fibers will be seen.
• High signal will be present on T2 sequences due
  to edema in the acute phase. Fibers in the
  expected location of the ACL will appear loose
  and disrupted rather than straight and taut.
• The origins of the torn ACL may or may not be
  readily identifiable.
• Although a complete tear of the ACL can usually
  be diagnosed with confidence, MR is not reliable
  in the diagnosis of partial ACL tears.

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