Triangles in Surgery #

1. Hesselbach’s Triangle #

• Borders:
  • Medial: Rectus sheath
  • Superolateral: Inferior epigastric artery
  • Inferior: Inguinal ligament
• Importance: Helps in differentiating direct from indirect hernias.

2. Bryant’s Triangle #

• Formation:
  • Patient lies supine
  • Line 1: From the anterior superior iliac spine vertically down to the bed
  • Line 2: From the tip of the greater trochanter to join Line 1 at right angles
  • Line 3: From the anterior superior iliac spine to the tip of the greater trochanter
• Importance:
  • Diminution in the length of Line 2 indicates upward displacement of the greater trochanter.
  • Line 3 helps determine the anteroposterior displacement of the greater trochanter.

3. Triangle of Doom #

• Borders:
  • Medially: Ductus deferens
  • Laterally: Spermatic vessels
  • Apex: At the level of internal inguinal ring
• Importance: Contains the external iliac artery and vein, and the femoral nerve. Stapling is avoided in this triangle during laparoscopic preperitoneal repair for hernia.

4. Calot’s Triangle #

• Borders:
  • Medially: Common hepatic artery
  • Laterally: Cystic duct
  • Apex: Junction of the cystic and hepatic ducts
  • Base: Cystic artery
• Importance: Contains the cystic lymph node of Lund.

5. Anal Triangle and Urogenital Triangle #

• Formation:
  • A transverse line joining the anterior parts of the ischial tuberosities and passing immediately anterior to the anus divides the perineum into two triangles: anal and urogenital.
• Importance: Common sites of abscess in the perineal and ischiorectal spaces.

6. Femoral Triangle #

• Borders:
  • Medially: Medial border of adductor longus
  • Laterally: Medial border of sartorius
  • Apex: Meeting point of the medial and lateral boundaries
• Importance: Suitable site for intravenous injection in infants; femoral artery pulsations aid in diagnosing peripheral vascular disease.

7. Lumbar Triangle #

a. Inferior Lumbar Triangle (Triangle of Petit) #

• Borders:
  • Below: Crest of ilium
  • Laterally: External oblique
  • Medially: Latissimus dorsi
• Importance: Common site for primary lumbar hernia.

b. Superior Lumbar Triangle (Grynfelt’s Triangle) #

• Borders:
  • Above: 12th rib
  • Medially: Sacrospinalis
  • Laterally: Posterior border of the inferior oblique
• Importance: Site for Grynfelt hernia.

8. Triangle of Auscultation #

• Borders:
  • Medially: Lateral border of the trapezius
  • Laterally: Medial border of the scapula
  • Inferiorly: Upper border of latissimus dorsi
• Floor: 7th rib, 6th and 7th intercostal spaces, rhomboids minor
• Importance: Best site for auscultating respiratory sounds; previously used for detecting sounds of swallowed liquids before X-rays.

9. Simon’s Triangle #

• Borders:
  • Anteriorly: Recurrent laryngeal nerve
  • Posteriorly: Common carotid artery
  • Base: Inferior thyroid artery
• Importance: Aids in the identification of the recurrent laryngeal nerve.

10. Lumbosacral Triangle (Marcille’s Triangle) #

• Borders:
  • Medially: Body of the 5th lumbar vertebra
  • Laterally: Medial border of the psoas muscle
  • Apex: Junction of the psoas major muscle and the body of the 5th lumbar vertebra
  • Base: Upper surface of the ala of the sacrum
  • Floor: Transverse process of the 5th lumbar vertebra and the iliolumbar ligament
• Importance: Ureter crosses the common iliac vessels at the lateral angle of the triangle.

11. Retromolar Trigone #

• Borders:
  • Base: Overlies the ascending ramus of the mandible from the last molar
  • Apex: Terminates at the maxillary tuberosity
  • Laterally: Continuous with the buccal mucosa
  • Medially: Blends with the anterior tonsillar pillar
• Importance: Common site for oral malignancy.

12. Sherren’s Triangle #

• Borders:
  • Umbilicus
  • Symphysis pubis
  • Anterior superior iliac spine
• Importance: Indicates the area of hyperesthesia in an acute episode of appendicitis.

13. Scalene Triangle #

• Borders:
  • Anteriorly: Scalenus anticus
  • Posteriorly: Scalenus medius
  • Inferiorly: First rib
• Importance: Subclavian artery and trunks of the brachial plexus pass through the scalene triangle, where they may be compressed, causing thoracic outlet syndrome.