Purpose of the Bony thorax?
The bony thorax supports the walls of the pleural cavity and the diaphragm used in respiration
What is the bony thorax formed by?
The bony thorax is formed by the sternum, 12 pairs of ribs, and 12 thoracic vertebrae
Position of the Sternum?
The sternum, or breastbone is directed anteriorly and inferiorly and is centered over the midline of the anterior thorax.
Describe the sternum...
a narrow flat bone about 6 inches in length, the sternum consist of 3 parts: manubrium, body and xiphoid process.
What does the sternum support?
supports the clavicles at the superior manubrial angles and provides attachment to the costal cartilages of the first seven pairs of ribs at the lateral borders.
Describe the manubrium...
The manubrium, the superior portion of the sternum, is quadrilateral in shape and is the widest portion of the sternum.
posterior on each side of the jugular notch is an oval articular facet that articulates with the sternal extremity of the clavicle
Body of the sternum
is the longest part of the sternum (4 inches) and is joined to the manubrium at the sternal angle
is the distal and smallest part of the sternum it is cartilaginous in early life and partially or completely ossifies, particularly the superior portion in later life
How are the ribs numbered?
12 pairs of ribs are numbered consecutively from superiorly to inferiorly
How are the ribs situated?
on an oblique plane so that their anterior ends lie 3-5 inches below the level of their vertebral ends
articulate with the C7 vertebrae but rarely attach to the sternum, they may be free or fuse with the first rib
Parts of the ribs
head, a flattened neck, a tubercle, and a body, the ribs have facets on their heads for articulation with the vertebrae
Describe the sternoclavicular (SC) joints...
are the only points of articulation between the upper limbs and the trunk
Describe the Costovertebral Joint
posteriorly the head of the rib is closely bound to the demifacets of two adjacent vertebral bodies to form a synovial gliding articulation
Describe the Costotransverse joint & Costovertebral joint
the tubercle of a rib articulates with the anterior surface of the transverse process of the lower vertebra at the costotransverse joint, and the head of the rib articulates at the costovertebral joint
Describe the Costochondral articulations
The Costochondral articulations are found between the anterior extremities of the ribs and the costal cartilage, these articulations are cartilaginous sychondrosis and allow no movement
Describe the Sternocostal Joints
The articulation between the costal cartilages of the true ribs and the sternum
Respiratory Movement - quiet respirations
The normal oblique orientation of the ribs changes little during the quiet respiration movements; however the degree of obliquity decreases with deep inspirations and increases with deep expirations
Respiratory Movement - deep inspiration and expiration
On deep inspiration the anterior ends of the ribs are carried anteriorly, superiorly, and laterally while the necks are rotated inferiorly. On deep expiration the anterior ends are carried inferiorly, posteriorly, and medially while the necks are rotated superiorly
body habitus and position of the diaphragm
higher level in hyperstenic patients, and lower in hypostentic patients
how much does respiration move the diaphragm?
averages 1.5 inches between deep inspiration and deep expiration. Movement is less in hyperstenic patients, and more in hypostentic patients.
Why the second respiration?
because there is deeper inspiration and expiration and therefore greater depression or elevation of the diaphragm.
Why not do ribs supine?
the anterior ends of the ribs are less sharply visualized when the patient is in the supine position.
How do you determine if the patient should be radiographed supine or upright?
unless the change can be done with a tilting table, patients with recent rib injury should be examined how they arrive in the radiology department
Ambulatory patients supine or upright?
the ambulatory patient can be positioned for the recumbent images with minimal discomfort by bringing the tilt table to the vertical position for each positioning change, The patient stands on the footboard is comfortably adjusted, and is then lowered to the horizontal position.
Problems radiographing the sternum...
The sternum is located directly anterior to the thoracic spine, so an AP or PA projection provides little useful diagnostic information. To separate the vertebrae and the sternum it is necessary to angle the CR about 15 degrees (deep chests less angle, shallow chests more angle).
Thorax thickness and central ray angulation
thorax thickness = 15cm, then CR angle = 22
thorax thickness = 30cm, then CR angle = 12
Sternum- PA Oblique RAO
SID = 30, 15-20 degree rotation, place top of IR about 1.5 inches above jugular notch, shallow breaths during exposure, unless short exposure time then suspend on expiration, CR enter elevated side at T7 and 1 inch lateral to msp
Sternum- PA Oblique (Moore's Method) Modified Prone
SID = 30, for ambulatory patients that is more comfortable, bend at waist and put sternum in center of table while standing, CR angled 25 degrees (less for large patients, and more for thin) respiration-slow shallow breathing or a low ma with 1-3 seconds use end of expiration
Sternum- Lateral (Upright)
SID = 72 to reduce magnification, have patient rotate shoulders posteriorly and lock hands behind back, adjust to true lateral, IR 1.5 inches above jugular notch, suspend on inspiration (sharper contrast), CR perpendicular to IR
Sternoclavicular Articulations - PA (Prone)
Center at 3rd Vertebrae or Jugular Notch, arms by side, palms upward, for bilateral pt head goes on chin so msp is vertical, for single head toward affected side, suspend on expiration, CR perpendicular to T3
Sternoclavicular Articulations - PA Oblique Projection (Body Rotation Method) RAO or LAO
keep affected side down with an oblique angle to project the vertebrae well behind the SC joint closest to the IR (10-15 degrees), suspend on expiration, CR enters T2-T3 (3 inches distal to vertebral prominence, 1-2 inches lateral to MSP), if CR enters right then left SC joint is shown
Evaluating Criteria of Sternoclavicular Articulation PA Obliques
SC joint in center, Open SC joint space, SC joint of interest immediately adjacent to vertebral column with minimal obliquely
Size of IR for ribs?
35x43 cm IR should be used to identify the ribs involvement and determine the extent of trauma or pathological condition.
When is the left ribs clear from the heart?
LAO or RPO, these 2 positions place the right-sided ribs parallel with the plane of the IR and are reversed to obtain comparable projections of the left-sided ribs.
Technicals factors for Ribs?
Technical factors that result in a short scale radiograph are often used (above 70 kvp)