Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Overview

The acetabulum forms the socket of the hip joint and articulates with the femoral head.

For clinical and surgical understanding, it is divided into two structural columns, which are essential for:

• Interpreting acetabular fractures
• Planning surgical approaches

Several important vessels and nerves lie in close proximity and are at risk during trauma and surgery

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Columns of the Acetabulum

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Structural Concept

The acetabulum is divided into:

• Anterior column
• Posterior column

These columns form the load-bearing framework of the hip joint.

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Anterior Column

Components

• Anterior ilium
• Anterior acetabular wall
• Weight-bearing dome
• Superior pubic ramus

Function

• Provides anterior and superior support

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Posterior Column

Extent

• From obturator foramen
• Through posterior acetabular dome
• To greater sciatic notch

Function

• Provides posterior structural stability

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Ischiopubic Ramus

Formation

• Inferior pubic ramus
• Inferior ramus of ischium

Role

• Forms the inferior border of the obturator foramen

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Pelvic Structural Orientation

• The acetabulum can be visualized as an inverted “Y” structure
• Represents the relationship between anterior and posterior columns

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Vascular Anatomy Around the Acetabulum

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Obturator Artery

Origin

• Anterior division of the internal iliac artery

Course

• Travels within pelvis – passes through obturator canal

Branches

• Anterior branch
• Posterior branch
• Forms a vascular ring around the obturator membrane

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Acetabular Branch

• Travels through ligament of the femoral head
• Supplies a small portion of the femoral head

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Corona Mortis

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Definition

• Vascular connection between:
  • Obturator system (internal iliac)
  • External iliac system (often via inferior epigastric vessels)

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Location

• 3–7 cm from pubic symphysis
• Posterior and superior to the superior pubic ramus

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Clinical Importance

• At risk during:
  • Pelvic trauma
  • Fracture surgery
  • Ilioinguinal approach

 Injury may cause severe hemorrhage

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Superior Gluteal Artery

Course

• Passes through the greater sciatic notch

Clinical Relevance

• May be injured in:
  • Posterior column fractures
  • Posterior surgical approaches

 Risk increases with excessive retraction

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Medial Femoral Circumflex Artery

Importance

• Primary blood supply to the femoral head

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Risk of Injury

• Hip dislocation
• Improper surgical dissection (e.g., detaching quadratus femoris incorrectly)

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Surgical Tip

• Preserve a small tendon cuff to protect the deep branch

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Nerve Anatomy Related to the Acetabulum

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Sciatic Nerve

Relationship

• Lies close to the posterior acetabulum

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Incidence of Injury

• Most common nerve injury in acetabular trauma
• Occurs in ~10% of hip dislocations

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Clinical Examination

• Ankle dorsiflexion
• Toe dorsiflexion
• Sensation over dorsum of foot

Peroneal division most commonly affected

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Surgical Precautions

• Keep:
  • Hip extended
  • Knee flexed

 Reduces nerve tension

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Anatomical Relations

• Posterior to obturator internus
• Inferior to piriformis

 Variations may occur (e.g., nerve splitting)

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Protection

• Obturator internus acts as a buffer during retraction

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Superior Gluteal Nerve

Location

• Near greater sciatic notch

Risk

• Injury if dissection extends >5 cm above greater trochanter

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Consequence

• Weakness of:
  • Gluteus medius
  • Gluteus minimus

 Leads to Trendelenburg gait

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Inferior Gluteal Nerve

Function

• Supplies gluteus maximus

Risk

• Injury during posterior approaches

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Lateral Femoral Cutaneous Nerve

Course

• Passes beneath inguinal ligament
• ~2 cm medial to ASIS

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Risk

• Injury during ilioinguinal approach

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Clinical Effect

• Sensory disturbance over lateral thigh

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Summary Points

• Acetabulum consists of anterior and posterior columns
• Forms an inverted Y-shaped structure
• Key vessels:
  • Obturator artery
  • Corona mortis
  • Superior gluteal artery
  • Medial femoral circumflex artery
• Key nerves at risk:
  • Sciatic nerve
  • Superior gluteal nerve
  • Inferior gluteal nerve
  • Lateral femoral cutaneous nerve

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Clinical Takeaway

A thorough understanding of:

• Column anatomy
• Vascular relations
• Nerve proximity

is essential for:

• Accurate fracture management
• Safe surgical approaches
• Avoidance of major complications