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Diagnostic Imaging II Midterm Exam Study Guide
Dr. Stecher - Winter 2009

Anomalies and Normal Variants
1. What is the relation between occipitalization and basilar invagination?
Occipitalization is the non-segmentation (or separation) of C1 and the occiput. Fusion would help you differentiate congenital versus acquired. Would appear as no space b/t occiput and C1 on xray. Occcipitalization may exist in isolation or occur with basilar invagination and usually the encroachment (>8mm) of the odontoid into the foramen magnum (measured by McGregor’s line).

2. Where is posterior ponticle?
Common variant on C1 that contains the vertebral artery and the 1st cervical nerve. The condition may compress and traction the vertebral artery during neck manipulation.

3. What is the significance of George's line?
George’s line describes the line drawn along posterior surfaces of the vertebral bodies on lateral views. The line should make a smooth curve form C1 to C7 (also used in thoracic and lumbar). Disruption indicates a segmental anterolisthesis or retrolisthesis of one segment on another.

4. Why is an os odontoideum clinically significant?
The odontoid has broken off the body of C2 and it can be very dangerous to do a cervical adjustment. The joint is unstable (C1 can move independently of C2) and may be held together only by the transverse ligament. Often this anomaly is due to a childhood injury.

5. What are the radiographic differences between an anomalous block vertebra and an acquired fusion of the spine?
A Block vertebra is non segmentation of 2 adjacent segments resulting in decreased AP diameter, rudimentary disk (small disk space), apophyseal joint fusion (posterior arch fusion) and fusion of the SPs. Called a “wasp waisted” appearance. Problem is that it creates DJD at adjacent joints (i.e if C3-4 are blocked…C2 and C5 have issues). More likely to occur in cervical.

In acquired fusion of the spine (surgical) on the otherhand the disc is removed and the two adjacent vertebra are fused together. On xray no disc is seen since it has been removed. This is more common in the lumbar spine.

6. What is the significance of the spinolaminar junction and spina bifida oculta in the lateral view?
• Spina bifida oculta results in failure of fusion of the two posterior arch ossification centers producing a midline defect.
• Because the lamina fail to fuse, this generally leaves a cleft SP on AP view.
• Yet this spinolaminar junction is often not visible on lateral view

7. Why is it common to see disc space narrowing adjacent to a limbus vertebra and/or Schmorl’s node?
• It is due to an intra body herniation of disk material. The nucleus pulposus herniates through the vertebral endplate.
• It is usually due to trauma, but can also be due to a weak endplate or a pathologic process such as osteoporosis. Pain is usually asymptomatic.
• On lateral radiograph you see focal indentation into vertebral body with sclerotic margin. (Look like chips of the endplates) The herniation goes through the ring apophysis (the secondary growth center). See Picture on Right
• Associated disc usually narrowed.

8. How can you tell whether a rib at the cervicothoracic junction is a cervical rib or first rib?
• The orientation of the transverse processes
o If they point up, thoracic
o If they point down, cervical
o Cervical ribs are usually isolated to the C7 segment
o They are only bilateral 2/3 of the time.
o They may fuse to the 1st rib.
o Other symptoms of cervical ribs:
o Thoracic outlet syndrome, drooping of the shoulders and increased thoracic kyphosis.
o Cervical ribs are most common at C7, C6, C5.
o Articulation with TP differentiates from hyperplastic TP

9. What is a transitional lumbosacral vertebra?
• When you se an undifferentiated L5 or S1.
• Transverse process is spatulated (>19 mm vertically) unilaterally or bilaterally
• May form accessory joints with sacral alae or be fused to sacrum.
• L/S disc hypoplastic.
• Degeneration often present.

Dysplasias
1. Name a dysplasia that may present with tall stature and hypermobile joints?
MARFAN’S SYNDROME
• This is a disease of the connective tissue with abnormal collagen formation.

What complications may be associated with this condition?
• Consists of long, slender tubular bones, ocular abnormalities, and aneurysm of the aorta.
• Underdevelopment and hypotonicity of the muscular system contributes to joint laxity and dislocation
• Hip dislocations, genu recurvatum, patellar dislocations, and pes planus.
• Myopia and pectus excavatum.

2. What is the most common cause of dwarfism?
ACHONDROPLASIA - bone growth disorder responsible for 70% of dwarfism cases
What neurologic condition may these individuals have that affects the legs?
• In the infant, the small foramen magnum and hydrocephalus can lead to cord compression. In the adult, congenital spinal stenosis often leads to paraplegia.

3. Fragile osteopenic bones are associated with which dysplasia?
OSTEOGENESIS IMPERFECTA
Osteoporosis with abnormal fragility of the skeleton, blue sclerae, mb abnormal dentition

Trauma
1. What are the radiographic findings of new vs. old fractures?
Step defect (rounds over with time), zone of impaction (for a couple months), osteophytes (from increased DJD)

2. What are the possible long bone fracture orientations?
Transcervical, Intertrochanteric, Subcapital

3. What are the types of incomplete fractures of pediatric long bones and how do they differ?
Torus - buckling of cortex
Greenstick fractures - incomplete fracture - one side of the bone is broken, the other side is bent.
Bowing - bending with no obvious cortical defect
Growth plate fractures - specific locations due to increased growth during childhood.
[Dislocated "slipped" epiphysis of the femoral head (only older children 10-17 years)]

4. Which is the most common type of Salter Harris fracture?
The most common type of Salter Harris fracture is a TYPE II fracture, which goes through the growth plate and metaphysis
Type I: through growth plate no bone involvement
Type III: gp + epiphysis
Type IV: metaphysic + gp + epiphysis
Type V: compression of gp (have to compare to non-invovled side to dx)

5. What is the difference between a malunion and a nonunion fracture?
Nonunion of a fracture refers to the absence of healing in a fracture. Malunion of a fracture refers to the healing of a fracture with incorrect anatomical alignment (so it does fuse just incorrectly)

6. What significant finding is demonstrated in the APOM view with a Jefferson's fracture? See Pictures to Right
A Jefferson fracture is a burst fracture of the atlas (he mentioned in class to think of it like a life saver candy… when you try to break it, it usually breaks into many pieces rather than just a chip off the side). To qualify as a Jefferson fracture there needs to be at least one fracture in the anterior arch and one through the posterior arch as well. The APOM view is the open mouth view. With this view you will look for increased lateral paraodontoid space bilaterally. There will be lateral masses of C1 that have slid laterally (>3mm). Often times there is swelling present also.
Notice in the picture how there is lateral offset of C1 on C2 bilaterally

7. What is traumatic spondylolisthesis and what cervical level does it usually occur at?
Traumatic spondylolisthesis is also called Hangman’s fracture. It usually occurs at C2. It is a bilateral pedicle (pars) fracture, which is often the result of a MVA.

Hangman’s Fx

8. What are the key radiographic differences between an un-united secondary ossification center of the spinous process at the cervicothoracic junction and a clay shoveler's fracture?
A clay shoveler’s fracture (most common at C7):
Lateral view shows inferiorly displaced SP
AP view shows “double spinous process” sign (looks like 2 SP’s on a single vertebrae)
Un-united secondary ossification center of the SP:
Fracture will be displaced caudally with jagged edges

9. What is the most common fracture of the spine and how do you differentiate new from old? (hint: it occurs usually at T12-L2)
Differentiation of old versus recent compression fracture
Hemorrhage, hematoma, step defect, and zone of impaction indicate fracture less then 2 months old
Old fractures often show contiguous disc degeneration
Bone scans may show “hot spots” for up to 24 months

10. List and describe the unstable fractures of the pelvis.
Unstable fracture - one that may move during healing and result in neurologic damage. In the pelvis, a fracture that may cause significant organ or vascular damage.
Stable fracture - one that will not move during healing and poses no threat to the spinal cord/cauda equina. In the pelvis, no threat to organs or vasculature.

11. What is the most common type of acetabular fracture?
Central Acetabular Fracture (aka Explosion Fracture)

12. What is the most common hip (proximal femur fracture) and what age do these often happen in?
Subcapital Fracture. Often missed. Most common in the elderly, and women 2x as often as men

13. Name and describe the proximal femur fracture that happens only in adolescents.
Slipped Capital Femoral Epiphysis
• Patient is usually 10-15 yo
• Usually occurs during rapid adolescent growth period, the femoral neck slips up off the femoral head
• Actually a fracture (Salter-Harris Type I)
• 20-30% occur bilaterally
• Only about 50% have a history of trauma
• More common in males, but bilateral involvement more commonly in females
• If it is to be bilateral, the second slips within a year
Associated with:
• Renal osteodystrophy, rickets, radiation therapy

14. Which direction does the patella usually dislocate?
Usually superolateral dislocation: may also move horizontally or vertically

15. What is a Jones’ fracture and what bone does it occur in?
Most common foot injury. Dancer’s fracture. The transverse fracture of the base of the 5th metatarsal. Usually more transverse.

16. Name an associated injury that must be evaluated for when a patient presents with a calcaneal compression fracture.
10% are associated with thoracolumbar spinal fxs- either compression or burst- must rule these out
Calcaneus is the most frequently fx tarsal bone- fx line often cannot be visualize therefore neet Boehler’s angle. Less than 28 deg = compression fx

17. What are the different types/grades of acromioclavicular joint sprain?
The three landmarks used:
Acromioclavicular joint space
• Should be bilateral and symmetrical, within 2-3 mm of each other, and averages between 2-4 mm in absolute width
Acromioclavicular alignment
• Inferior margins of the clavicle and opposing acromion should be smooth and horizontal
Coracoclavicular distance
• Normally 11-13mm (distance between inferior margin of the clavicle and the closest surface of the coracoid)
• There should be no more than a 5mm difference between right and left
Classification of AC injuries:
• Type I: Mild Sprain
• Acromioclaviclar ligament is stretched
• Coracoclavicular lig is intact
• Wt bearing doesn’t increase joint space or alter alignment
• Normal radiograph
• Type II: Moderate Sprain
• Acromioclavicular ligament is torn
• Coracoclavicular lig is stretched
• Widened jt space, slight elevation of clavicle possible
• Type III: Severe Sprain
• Acromioclavicular ligament disrupted
• Coracoclvicular ligament disrupted
• Widened joint space
• Elevation of distal clavicle above acromion
• Coracoclavicular space > 5mm than contralateral side
Type I and II can be managed conservatively, type III requires joint repair and open fixation


18. What is the radiographic difference in anterior vs. posterior glenohumeral dislocations? Which is most common?
• ~95% of glenohumeral dislocations are anterior
Anterior:
Humeral head may settle in: Radiologic signs:
subcoracoid (most common) Inferior and medial displacement
subglenoid Altered humeral head shape
subclavicular Hill-Sachs defect
intrathoracic Bankart lesions – inferior glenoid fx
Posterior:
Humeral head looks identical in external and internal rotation, because of fixation in its posteriorly displaced position. Humeral head often stays at same level as glenoid or superior to it.
Caused by epileptic convulsions, electric shocks, and direct trauma

19. What are Hill-Sachs/Hatchet and Bankart lesions and what are they associated with?
Hill-Sachs/Hachet defect is an impaction fx of the posterolateral humeral head (Best seen on AP with internal rotation, and even better on MR). Bankart lesions are inferior glenoid fxs seen with anterior glenohumeral joint dislocation. Hill-Sachs/Hachet defect and Bankart lesions are both associated with anterior dislocation of the humerus from the glenohumeral joint and fracture of the inferior glenoid rim from a posterior impaction injury.

20. Which part of the clavicle most commonly fractures?
Middle Clavicle Fx is most common (80%)—medial fragment displaces superiorly due to pull of the SCM, the distal fragment displaces inferiorly due to the weight of the shoulder and upper extremity.

21. What is the significance of the elbow fat pad signs (anterior and posterior)?
. The significance of elbow fat pad signs is that they are clinical signs of an intraarticular fx of the elbow with displacement of the anterior and/or posterior fat pads from between the fibrous and synovial layers of the humeral joint capsule. Not normally visible, the fat pads become visible from the intraarticular effusion and edema. 90% of children’s elbow fxs have visible posterior fat pads (less frequently seen in adults; absence of sign doesn’t preclude fx).

22. What structures are involved in the most common fractures of the elbow in children and in adults?
Structures most commonly involved with elbow fxs in children is supracondlyar fxs (transverse or oblique fx above condyles) of the distal humerus (60%), and in adults is radial head and neck fxs (50%) (usually viewed as vertically oriented radiolucent fx lines; “Chisel fx”). Adults second most common elbow fx at olecranon (20%).

23. What are the most common wrist fractures seen in each of the following age groups: children, young adults, elderly?
Most common wrist fx: children(6-10yo)—Distal Radius Torus Fx; usually 2-4cm proximal to distal growth plate;

Young adults(15-40yo)—Scaphoid Fx; occult fx, acute fx line may not be visible until 20 days post-injury, 70% at scaphoid waist;

Elderly—Colles’ Fracture (from fall on outstretched hand); distal radius fxed ~20-35mm proximal to jt surface, distal fragment is angulated posteriorly, and in 60% of cases the ulnar styloid is also fxed .

24. Describe the difference between Colles' and Smith's fractures at the wrist.
-Colles’s fx goes posterior “The collie goes in the back door” --FOOSH fx so wrist is exteneded
-Smith’s fx goes anterior “Mr. & Mrs. Smith go in the front door”--fx dt fall with wrist in hyperflexion therefore “Reversed” Colle’s fx

25. Discuss the vascular supply of the scaphoid and its effect in avascular necrosis and healing of this structure after fracture.
The scaphoid has three anatomical areas: proximal pole, waist, and distal pole. There are only two sources of blood supply to the scaphoid, one to the waist and one to the distal pole. The proximal pole does not have its own bld supply therefore a fx at the proximal pole can lead to AVN dt lack of blood supply and subsequent inability to heal. AVN can be dxed via x-ray bc it will show up whiter than the surrounding bone.

26. What is the most common carpal bone to dislocate and in what direction?
The Lunate is the most frequently dislocated carpal—is dt a Hyperextension injury
The Lunate tilts forward and anteriorly thus isrupting its articulation with the capitate, but maintains close approximation with the anterior rim of the radius
Lateral view displays the anterior tilt
PA view - Lunate looks like a triangle, apex points distally – “pie sign”

27. What are barroom and boxer’s fractures of the hand?
Boxer’s Fracture: Transverse fracture of second or third metacarpal neck
Caused by impact of short, straight jabbing blow
Barroom Fracture: Transverse fracture of fourth or fifth metacarpal neck
Caused by “roundhouse” blow
• Barroom and boxer’s fracture result in anterior angulation of the metacarpal head and shortening and rotation of distal fragment

28. What is gamekeeper’s thumb?
First metacarpophalangeal tear or rupture of the ulnar collateral ligament
Abduction stress view of thumb shows widened ulnar side of MCP joint, indicating instability
May have a chip fracture, with small fragment from ulnar margin of proximal phalanx base
MRI will demonstrate ulnar collateral ligament lesion

29. What are the common sites of a stress fracture?
Most common locations:
• Metatarsals – aka “march fracture”, “deutchlanders disease”
• Proximal tibia,
• calcaneus,
• distal fibula,
• hook of the hamate,
• distal one third of the clavicle
• L5 pars interarticularis (most common stress fracture in the spine)

30. How can stress fractures be detected on plain x-ray?
Often occult; requires bone scan or delayed plain film images (latent period = 10-21days)
50% of stress fxs never show x-ray findings
(decent description of imaging stress fractures on emedicine http://emedicine.medscape.com/article/397402-imaging )


What imaging type(s) are most sensitve in detecting stress fractures?
Bone scan is sensitive, not specific
CT may delineate fx but later
MRI will show bone edema and fx line earlier than CT
Sensitive and specific
Periosteal response: local periosteal and endosteal cortical thickening

Spondylolisthesis

1. What are the most common types of spondylolisthesis in the lumbar spine?
• 90% of all spondylolytic spondylolistheses involve the L5 segment.
• Most degenerative spondylolistheses occur at L4.

2. Discuss the differences between spondylolytic spondylolisthesis and degenerative spondylolisthesis. Make sure to include the etiology of each and what spinal level are they most common at.

Spondylolytic spondylolisthesis : anterior displacement of a vertebra
-Etiology:
biomechanical stress –
usually results in pars interarticularis fracture (spondylolysis)
Spondylolysis is the most common cause of spondylolisthesis in pediatric patients
-3 Subtypes:
Subtype a: Most common - it is a stress (fatigue) fracture. Subtype b: Elongation of pars without defect due to repeated stress fracture with healing. Subtype c: Acute pars fractures but are rare.
-Spinal level-
Usually at L5 in young active individuals (extension activity - wrestlers, gymnasts, high jumpers).
Spondylolysis: a defect in the pars interarticularis of a vertebra
-Etiology:
Repetitive microtrauma Congenitally slender pars may predispose to stress fracture Acute fracture -rarely Not recorded in infants
Stress fracture factors
Fatigue fx caused by mechanical stress at L/S lordosis Hyperextension loading (carrying heavy backpack) Onset M/C after 5 yo – probably d/t upright posture and ambulation Premature walking Divers, gymnasts, pole-vaulters, weight-lifters Non-union d/t lack of immobilization

Degenerative spondylolisthesis:
Consists of disc space loss and loss of cartilage in the facet joints which allows the superior vertebra to slip forward. Not more than 15-25% anterior slip. Most common at L4, females, and over 40 years of age. No neural arch defect.

3. What is the Meyerding’s grading system?
Lateral lumbar projection. The sacral base is divided into 4 equal sections. Grade 1 The posterior-inferior corner of L5 is aligned with the first division 1 to 25%
Grade 2 “ “ second division 26 to 50%
Grade 3 “ “ third division 51 to 75%
Grade 4 “ “ fourth division 76 to 100%
Grade 5 is spondyloptosis (L5 anterior to S1) >100%

Several methods exist for radiographically characterizing the degree of spondylolisthesis. The most common is the Meyerding classification in which the degree of subluxation is described as the percentage of translation of the upper VB over the lower one. The categories include Grade I (0-25% subluxation), Grade II (25-50% subluxation), Grade III (50-75% subluxation), and Grade IV (75% subluxation).[16,17] Complete or 100% spondylolisthesis is termed spondyloptosis (Fig. 3).
Whereas the Meyerding classification only takes into account translational subluxation, other measurements take into account the angular displacement that can occur in spondylolisthesis. The "slip angle" or sagittal rotation measures the degree of lumbosacral kyphosis. This is calculated by measuring the angle formed by the intersection of two lines: 1) a tangent to a line drawn along the posterior aspect of the sacrum; and 2) a line parallel to the inferior endplate of L-5. In the normal situation, the angle formed by the intersection of these two lines measures zero. The "tilt" or sacral inclination refers to the vertical position of the sacrum, which is measured by drawing a line perpendicular to the floor and measuring the angle formed by the intersection of this line with a second one drawn parallel to the posterior aspect of the sacrum. Usually this angle should be greater than 30°; as the sacrum obtains a more vertical position, this angle becomes progressively smaller.[3,11,16,29]

4. What is an inverted/ reversed Napoleon hat sign?
• Inverted Napoleon’s hat sign or bowline of Brailsford seen with significant anterolisthesis.
- On imaging the body of L5 slides forward enough to give a look of an upside down Napoleon hat. This only occurs if there is significant slippage of anterior portion of L5 off of the sacrum. There is bilateral pars fracture of the vertebrae that allows this slippage. There isn’t necessarily nerve damage or impingement as the cauda equine will follow normal path.

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