Bony Thorax - Sternum and Ribs Flashcards
Sternum
- Part of the bony thorax, which also includes the lungs and 12 pairs of ribs.
Topographic Landmarks
- Jugular Notch: Located at T2-T3 vertebral level.
- Sternal Angle: Located at T4-T5 vertebral level.
- Xiphoid Tip: Located at T9-T10 vertebral level.
- Sternoclavicular Joint Located at T1 vertebral level
Sternum Components
- Manubrium: The superior portion of the sternum.
- Body (Corpus or Gladiolus): The main, elongated part of the sternum.
- Xiphoid Process: The small, inferior tip of the sternum, situated anteriorly at the level of T9-T10.
Sternal Rib Articulations
- The sternum articulates with the clavicles at the jugular notch and with the costal cartilages of the first seven ribs.
- Specific rib articulations:
- Facet for the 1st costocartilage is present.
- Articulations for the 2nd through 7th ribs are evident along the body of the sternum.
Ribs
Typical Rib Anatomy (Inferior View)
- Vertebral End (Posterior): Part of the rib that articulates with the vertebrae.
- Head: The expanded end that articulates with the vertebral body.
- Neck: Connects the head to the tubercle.
- Tubercle: A small eminence that articulates with the transverse process of a vertebra.
- Angle: The point where the rib curves sharply.
- Shaft (Body): The main, elongated portion of the rib.
- Sternal End (Anterior): The end that connects to the costal cartilage.
- Groove for blood vessels and nerve (Costal Groove): Located on the inside margin of the rib.
Articulations of the Bony Thorax
- Costotransverse Joint (F): Synovial joint with plane (gliding) motion; diarthrodial.
- Costovertebral Joint (G): Synovial joint with plane (gliding) motion; diarthrodial.
Oblique Sternum Considerations
- RAO (Right Anterior Oblique): Used to project the sternum away from the spine.
- The degree of obliquity depends on the patient's body habitus (e.g., large, barrel-chested thorax vs. thin-chested thorax).
- A larger patient requires less obliquity (15 degrees) compared to a thinner patient (20 degrees).
Technical Considerations for Sternum
- Breathing Technique: Orthostatic (shallow breathing) technique with a 2-3 second exposure time.
- kVp Range:
- Analog: 65-75
- Digital Systems: 70-80
- SID (Source-to-Image Distance): 40 inches (102 cm); never use an SID less than 38 inches (97 cm) or 15 cm.
RAO Sternum: Orthostatic (Breathing) Technique
- Erect position, if possible.
- Expose on inspiration.
- kVp Range:
- Analog: 65-75
- Digital Systems: 75-85
RAO Sternum Specifics
- Degree of Obliquity: 15° to 20° RAO.
- Central Ray (CR): To the center of the sternum, approximately 1 inch (2.5 cm) to the left of the midline and midway between the jugular notch and xiphoid process.
- Trauma Alternative: 15° to 20° cross angle, grid landscape.
Evaluation Criteria: RAO Sternum
- Entire sternum visualized.
- Sternum superimposed over the heart shadow.
- Correct rotation.
- Optimal exposure factors.
Lateral Sternum
- Position: Horizontal Beam Lateral.
- Central Ray (CR): To the center of the sternum.
- SID: 60-72 inches (152-183 cm).
Evaluation Criteria: Lateral Sternum
- Entire sternum visualized.
- No rotation.
- Optimal exposure factors.
PA Sternoclavicular (SC) Joints
- Position: True PA.
- Central Ray (CR): Perpendicular to T2-T3 (3 inches/7 cm distal to vertebra prominens).
Evaluation Criteria: PA SC Joints
- Medial portion of clavicles and SC joints visualized.
- No rotation.
- Optimal exposure factors.
Anterior Oblique: RAO for Right SC Joint
- Rotation: 10° to 15° rotation.
- Central Ray (CR): To the level of T2-T3.
Evaluation Criteria: RAO for SC Joint
- Manubrium and medial clavicle visible.
- SC joint open and shifted away from the spine.
- Optimal exposure factors.
Rib Routine
Basic Rib Routine
- AP or PA projection (area of injury closest to the Image Receptor (IR)).
- Unilateral or bilateral study (follow department protocol).
- Axillary portion of ribs - 45° anterior or posterior oblique position (rotate spine away from side of interest).
- Optional: Chest study if pulmonary injury is suspected.
AP Ribs
- Above Diaphragm:
- CR 3-4 inches (8-10 cm) below the jugular notch.
- Expose on inspiration.
- Below Diaphragm:
- CR midway between the xiphoid process and lower ribs.
- Expose on expiration.
Evaluation Criteria: AP Ribs Above Diaphragm
- 1st to 10th posterior ribs visualized above the diaphragm.
- No motion.
- No rotation.
- Optimal exposure factors.
Evaluation Criteria: AP Ribs Below Diaphragm
- 9th to 12th ribs visualized.
- No motion.
- No rotation.
- Optimal exposure factors.
Positioning Considerations for Ribs
- Ribs Below Diaphragm:
- Recumbent position.
- Expiration.
- Area of Interest: Position the area of interest closest to the IR (AP or PA).
- Axillary Ribs: Rotate the spine away from the area of interest to elongate.
- Marking Site of Injury: Ensure appropriate marking.
- Chest Study: Consider a chest study if pulmonary injury is suspected.
- LPO (Left Posterior Oblique): Elongates left posterior and axillary ribs.
Posterior or Anterior Oblique: Ribs Above Diaphragm
- 45° oblique.
- CR to T7 level.
Posterior Oblique: Recumbent
- 45° oblique.
- CR midway between the xiphoid process and iliac crest.
Evaluation Criteria: LPO Above Diaphragm
- Axillary portion of ribs appears elongated.
- No motion.
- Optimal exposure factors.
Important Considerations
- The xiphoid process does not become totally ossified until the age of 40 years.
- The anterior ends of the ribs do not attach directly to the sternum; they connect via costal cartilage.
- The 11th and 12th ribs are classified as floating ribs.
- The costal groove contains blood vessels and nerves.
- For a PA projection of the SC joints, the CR is centered at the level of T2-T3.
- The ideal, general position for a study of the ribs below the diaphragm is recumbent.
- For an injury to the left, upper anterior ribs, avoid exposure upon expiration.
- A hypersthenic patient requires greater rotation of the sternum for the RAO projection as compared with a sthenic patient - FALSE.