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.