Bony thorax - sternum and ribs - Ch 11

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bony thorax function

to serve as an expandable bellowslike chamber
protects organs of resp. sys and heart and great vessels

bony thorax consists of

sternum
thoracic vertebrae posteriorly
12 pairs of ribs

site for marrow biopsy

the sternum - local anesthesia is inserted into marrow cavity to get a sample of the rbm

sternum parts

manubrium
body
xiphoid process

manubrium

upper portion of sternum - 2 inches avg

body of sternum

longest part of sternum
4"
union is not complete until age 25

xiphoid process

most inferior part of sternum
cartilage during infancy and youth
doesn't ossify until age 40
small but can vary in size, shape and degree of ossification

jugular notch

uppermost border of the manubrium
T2-T3

other names for the jugular notch

suprasternal or manubrial notch - b/w clavicles and manubrium

sternal angle

where the lower end of manubrium joins the body - palpable
T4-T5

xiphoid process

T9-T10

inferior costal angle (rib)

L2-L3

sternoclavicular articulation

clavicle and manubrium articulation
only bony connection b/w each shoulder girdle and the bony thorax

how many pairs of ribs join the sternum

7 - union is cartilage

facet

articulation with cartilage of ribs

costocartilage

term for short piece of cartilage that connects anterior ribs to sternum

2nd costocartilage connects at the level of the

sternal angle

Ribs 8, 9, and 10

have costocartilage, but connect to the number 7 costocartilage instead of directly to the sternum

First 7 pairs of ribs

true ribs - because they connect directly to the sternum

false ribs

last 5 pairs of ribs

floating ribs

false ribs 11 and 12 - do not possess costocartilage and do not connect to the 7th rib's costocartilage

two ends of the ribs

sternal end
vertebral end

between the 2 ends of the rib

shaft or body of the rib

vertebral end of rib consists of a

head - articulates with 1-2 thoracic vertebrae
neck - flattened
tubercle - articulates with transverse process of a vertebra, allows attachment for a ligament
angle - forward angulation, and downward

posterior (vertebral) end of a typical rib is

3-5" higher than the anterior (sternal) end

On a radiograph, the most superior part of the rib is

the posterior end or end nearest the vertebrae

lower inside margin of each rib protects an

artery, a vein and a nerve

rib injuries

very painful
associated with substantial hemorrhage

costal groove

inside margin that contains the blood vessels and nerves

first ribs of the rib cage are

short and broad and most vertical
most sharply curved

ribs get

longer and longer down to the 7th rib

From the 7th rib, ribs get

shorter and shorter

bony thorax is widest at the

lateral margins of the 8-9th ribs

costochondral union/junction

b/w the costocartilage and sternal end
synarthrodial - no movement permitted
cartilage and bone are bound by periosteum of the bone itself

sternoclavicular jt

synovial, permit plane/gliding motion
diathrodial

sternocostal jt of rib 1

cartilage of 1st rib and manubrium - no motion - synarthrodial
cartilaginous, synchondrosis

sternocostal jt of rib 2-7

b/w costocartilage and sternum - synovial
plane/gliding - diarthrodial

interchondral jt

b/w costal cartilages of #6-10 ribs - synovial, gliding, diarthrodial - for breathing process

costotransverse jts and costovertebral jts

synovial, gliding, diarthrodial

since sternum is on same plane as spine,

patient needs to be rotated 15-20° RAO

the 15-20° RAO position

shifts the sternum to the left of the thoracic vertebrae and into the homogenous heart shadow

Degree of obliquity required is dependent on the size of the

thoracic cavity
shallow/thin chest - requires MORE rotation to cast sternum away from thoracic spine. - 20°
barrel chest requires 15°

sternum is made of

spongy bone with thin layer of hard, compact bone surrounding it

kVp for sternum

65-70 kVp

breathing technique for sternum

shallow breaths to blur lung markings overlying the sternum
requires 65±5 kVp, low mA and long exposure time of 2-3 seconds

SID for sternum

40"
used to use a lower SID to create magnification of overlying ribs and sternum - increased exposure to pt, so not recommended

skin should be at least

15 inches (38cm) from collimator

patient history should include

nature of complaint - acute vs chronic, how injury occurred
location of rib pain or injury
if injury is caused by trauma to thoracic cavity - does pt have difficulty breathing
Is pt able to stand

ribs above diaphragm

upper 10 posterior ribs
Take radiograph erect if able
suspend on inspiration
low kvp - 65-70 because of lung tissue - lower kVp allows better visualization
If injury is over heart area - higher kVp may be needed to visualize ribs thru heart shadow and lung fields

when erect,

Gravity lowers diaphragm
Allows deeper inspiration

for above the diaphragm, breathing should be

suspended during inspiration

ribs below diaphragm

lower ribs
take recumbent - allows the diaphragm to rise to highest position and results in less thick abdomen (especially on bigger pts, because abdomen flattens when recumbent) Provides better visualization of lower ribs through abdominal structures
Suspend on expiration - allows diaphragm to rise to level of 7th or 8th posterior ribs - providing uniform density for below ribs

when recumbent for lower ribs,

allows the diaphragm to rise to highest position
results in less thick abdomen (especially on bigger pts, because abdomen flattens when recumbent)

for below the diaphragm, breathing should

suspended on expiration

recommended projection

place area of interest closest to IR
rotate spine AWAY from area of interest to prevent superimposition

if left posterior ribs are injured, use a

straight AP and a
LPO - moves spinous processes away from the left side and reduces foreshortening of ribs

if right ANTERIOR ribs are injured, us a

straight PA and a
LAO - moves spinous process away from site of trauma and elongates axillary portion of right ribs

BB marker

ensures radiologist is aware of the location of the trauma or pathology - each tech should determine dept protocol first

trauma to the bony thorax, respiratory system, history or rib injuries may also require

PA chest and
Lateral chest
to rule out pneumothoras, hemothorax, pulmonary contusion or other chest patholgoy

if pt cannot be erect for chest radiographs,

air-fluid levels must be ruled out, and a horizontal beam projection in decub position s/b included

pediatrics

pt motion and safety
immobilization
guardian with lead to hold pt
short exposure time, high mA
breathing technique is not indicated for pediatrics
collimation

Geriatric

fear of falling
radiolucent mattress or pad
blankets
decrease in kV or mAs
tremors require short exposure time, and high mA

digital considerations

correct centering and close collimation
ALARA
EI review may indicate a reduction in mAs is possible for future exposures

CT

provides cross sectionaly images of the bony thorax. Skeletal detail and associated soft tissues - good for evaluating sternum and/or sternoclavicular jts

nuclear med

radionuclide bone scan detects skeletal pathologies of thoracic cage (metastases, occult fx) - radiopharmaceutical-tagged tracer element is injected - and will demo hot spots - increased bone activity - abnormal area is investigated with radiography.

Bone scans are usually common practice for

pts who are at risk or symptomatic for skeletal metastases (except multiple myeloma)

fx

break in the structure of a bone

fx of bony thorax can be

dangerous due to proximity of lungs, heart and great vessels

rib fx

most commonly caused by trauma or underyling pathology

fx of 1st rib

associated with injury to underlying arteries/veins - disruption of bony cortex of rib, linear lucency thru the rib

fx of ribs 8-12

associated with injury to adjacent organs such as the spleen, liver or kidney - disruption of bony cortex of rib, linear lucency thru the rib

any rib fx may cause

injury to the lung or cardiovascular structures (pneumothorax, pulmonary or cardiac contusion)

flail chest

fx of adjacent ribs in 2 or more places caused by blunt trauma and associated with underlying pulmonary injury. Can lead to instability of chest wall - disruption of bony cortex of rib, linear lucency thru the rib

sternum fx

caused by blunt trauma, associated with underlying cardiac injury - disruption of bony cortex of sternum, linear lucency or displaced sternal segment

pectus carinatum (pigeon breast)

congenital defect - caused by anterior protrusion of the lower sternum and xiphoid process - usually benign condition but could lead to cardiopulmonary complications in rare cases

pectus excavatum (funnel chest)

congenital defect - deformity - depressed sternum. Rarely interferes with respiration but often is corrected surgically for cosmetic reasons

metastases

malignant neoplasms that spread to distant sites via blood and lymphatics. Ribs are common sites of metastatic lesions

osteolytic

destructive lesions with irregular markings - irregular margins and decreased density

osteoblastic

proliferative bony lesions of increased density

combo of osteolytic and osteoblastic

moth-eaten look - results from mix of destructive and blastic lesions

osteomyelitis

localized or generalized infection of bone and marrow associated with postop complications of open heart surgery, which requires sternum to be split. Most common cause - bacterial infection- erosion of bony margins

RAO sternum rotation

15-20° - 15 for larger, 20 for thinner

If recumbent RAO sternum can't be done

do LPO or supine with 15-20° mediolateral angle

kVp for lateral sternum

70-75

kVp for ribs below the diaphragm

70-80

CR for sternoclavicular jts

T2-T3 (3" distal to vertebra prominens)

Arms for lateral sternum

drawn back

SID for lateral sternum

60-72" or use 11x14 if can only use 40"

SID if doing bilateral PA/AP ribs

72" to minimize magnification AND pt dose

For posterior ribs do AP or PA?

AP

respiration for above diaphragm

suspend on inspiration

respiration for below diaphragm

suspend on expiration

Oblique rotation for sternoclavicular jts

10-15°
Less obliquity 5-10° to visualize OPPOSITE jt next to vertebral column

When will a PA and lateral chest be requested

to rule out pneumothorax, hemothorax

For right axillary ribs, do

LAO or RPO

CR for above the diaphragm ribs

T7 - 3-4" below jugular notch

CR for below the diaphragm ribs

midway between xiphoid process and lower costal margin

IR for above the diaphragm ribs

1.5" above shoulder

IR for below the diaphragm ribs

at iliac crest

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