Surface anatomy for clinical procedures

Surface Anatomy - Mapping the Body

• Key Thoracic Landmarks:

  • Suprasternal Notch: Palpable dip, level with T2/T3 vertebrae.
  • Sternal Angle (of Louis): Manubriosternal joint, level with T4/T5 IV disc. Articulates with the 2nd rib. Marks aortic arch & tracheal bifurcation.
  • Xiphoid Process: Level with T9 vertebra; inferior border of heart.

• Key Abdominal Landmarks:

  • McBurney's Point: Two-thirds from umbilicus to ASIS. Tenderness suggests appendicitis.
  • Mid-inguinal Point: Midway between ASIS & pubic symphysis. Femoral artery pulse/access.

⭐ The Sternal Angle is a vital landmark at the T4/T5 level, marking the 2nd rib, tracheal bifurcation, and aortic arch boundary.

Thoracic Landmarks - Navigating the Cage

• Sternal Angle (of Louis): Key palpable landmark. Articulates with the 2nd rib, the starting point for counting ribs and intercostal spaces (ICS).

  • Marks the level of the T4/T5 intervertebral disc.
  • Site of tracheal bifurcation into primary bronchi.
  • Location of the aortic arch.

• Intercostal Neurovascular Bundle: Runs along the inferior margin of each rib.

  • 📌 Mnemonic: VAN (Vein, Artery, Nerve) from superior to inferior.
  • For procedures (e.g., thoracentesis, nerve block), the needle is inserted superior to the rib below to avoid injury.

• Thoracentesis: Performed at mid-axillary line, typically in the 8th or 9th ICS during expiration.

⭐ The Sternal Angle marks the T4/T5 vertebral level, the bifurcation of the trachea, and the beginning/end of the aortic arch.

Abdominal Landmarks - Belly's Treasure Map

• Xiphoid Process: Sternum's inferior tip, superior abdominal boundary.
• Costal Margin: Lower border of the rib cage.
• Iliac Crest: Palpable superior border of the ilium, at the L4 vertebral level (lumbar puncture).
• Anterior Superior Iliac Spine (ASIS): Bony point at the anterior end of the iliac crest.
• Umbilicus: Scar at the T10 dermatome level.

---

Key Clinical Points:

• McBurney's Point: Located one-third of the distance from the ASIS to the umbilicus. Maximal tenderness here is a classic sign of acute appendicitis.
• Murphy's Point: Intersection of the right mid-clavicular line and the costal margin. Elicits Murphy's sign in acute cholecystitis.

⭐ The transpyloric plane, midway between the jugular notch and pubic symphysis, is a crucial horizontal plane transecting the pylorus, gallbladder fundus, and renal hila.

Limb Landmarks - Access & Nerve Blocks

• Upper Limb Access:
  • Axillary Sheath: Palpate axillary artery medial to coracobrachialis. Site for axillary nerve block targeting terminal brachial plexus branches.
  • Brachial Plexus Blocks: Interscalene (shoulder surgery; risk phrenic n. palsy), Supraclavicular (arm/forearm; risk pneumothorax).
  • Wrist: Median n. (b/w palmaris longus/FCR tendons), Ulnar n. (lateral to FCU tendon).
• Lower Limb Access:
  • Femoral Triangle: 📌 NAVEL (Lat→Med): Nerve, Artery, Vein, Empty Space, Lymphatics. Crucial for vascular access & femoral nerve block.
  • Sciatic Nerve Block: Midway between greater trochanter and ischial tuberosity.

⭐ Interscalene Block Complication: Anesthetizing the brachial plexus between the scalene muscles (C5-C7 roots/trunks) has a near 100% incidence of transient ipsilateral phrenic nerve palsy, causing diaphragmatic paralysis.

• Central line placement targets the internal jugular vein, found between the sternal and clavicular heads of the sternocleidomastoid muscle.
• Thoracentesis is safely performed in the midaxillary line at the 8th or 9th intercostal space to avoid lung or liver injury.
• Lumbar puncture aims for the L3-L4 or L4-L5 interspace, identified by the line connecting the iliac crests.
• McBurney's point, for appendicitis, is one-third the distance from the ASIS to the umbilicus.
• Cricothyrotomy provides emergency airway access through the cricothyroid membrane.