Fascia & Veins

EXTREMITY ANATOMY

Fascia and Veins of the Lower Limb

Lower Extremity Anatomy

  • Subcutaneous Tissue: The subcutaneous tissue of the hip and thigh is continuous with that of the inferior abdominal wall and buttock.

  • Knee Transition: At the knee, the subcutaneous tissue loses its fat and blends with the deep fascia.

  • Deep Fascia:

    • Description: Strong and inelastic connective tissue that invests the lower extremity (LE).

    • Function: Limits outward expansion of the contracting musculature; the increased pressure from muscle contraction “pumps” the blood proximally through the veins.

Deep Fascia of the Thigh (Fascia Lata)

  • Attachment Points:

    1. Inguinal ligament, pubic arch, body of the pubis, and pubic tubercle.

    2. Scarpa’s fascia of the inferior abdominal wall, attaching to the deep lower extremity fascia inferior to the inguinal ligament.

    3. Iliac crest (lateral & posterior).

    4. Sacrum, coccyx, sacrotuberous ligament, ischial tuberosity (posteriorly).

    5. Exposed parts of bones at the knee and deep fascia of the leg.

  • Enclosure of Muscles: The fascia lata encloses the large thigh muscles.

  • Iliotibial Tract:

    • Laterally, it forms a thickened portion of the fascia lata called the iliotibial tract, which serves as an aponeurosis for the tensor fasciae latae and gluteus maximus muscles.

    • Extends from the iliac tubercle to the anterior-lateral tibial tubercle (known as Gerdy’s tubercle).

Fascial Compartments of the Thigh

  • Structure:

    • The thigh contains three fascial compartments, each of which isolates blood supply and innervation.

    • Surrounded by the fascia lata and three intermuscular septa formed by deep extensions of the fascia lata that connect to the linea aspera of the femur.

  • Lateral Intermuscular Septum:

    • Strong, extending from the iliotibial tract to the lateral lip of the linea aspera and the lateral supracondylar line of the femur.

  • Other Intermuscular Septa:

    • Medial intermuscular septum.

    • Posterior intermuscular septum.

Saphenous Opening

  • Definition: A gap in the fascia lata located infero-lateral to the inguinal ligament and lateral to the pubic tubercle.

  • Margins:

    • Medial margin: Smooth.

    • Lateral margin: Sharp, forming the falciform ligament.

  • Cribiform Fascia: A sieve-like membrane covers the saphenous opening, permitting the passage of the Great Saphenous vein and lymphatics while occluding other areas.

Crural Fascia

  • Description: Deep fascia for the leg, continuous with the fascia lata.

  • Attachment: Attaches to the anterior and medial borders of the tibia and is continuous with the periosteum.

  • Variations in Thickness: Thinner distally but thickens to form extensor/flexor retinacula on both anterior and posterior aspects of the ankle.

Crural Fascia Structure

  • Intermuscular Septa:

    • Anterior and Posterior intermuscular septa passing from the deep crural fascia attach to the fibula’s margins.

  • Interosseous Membrane:

    • This membrane traverses from the tibia to the fibula.

  • Compartments:

    • Three (or four) compartments created:

    • Anterior Compartment: Houses dorsiflexors.

    • Lateral Compartment: Contains fibular (everter) muscles.

    • Posterior Compartment: Hosts plantarflexors.

    • The transverse intermuscular septum further divides the posterior compartment into deep and superficial compartments.

Lower Extremity Veins

Types of Veins

  • Deep Veins:

    • Accompany the arteries in vascular sheaths, allowing for arterial pulsation to assist in venous blood flow.

    • e.g., Popliteal vein joins the femoral vein in the popliteal fossa and is further joined by the deep vein of the thigh.

    • The femoral vein passes deep to the inguinal ligament to become the external iliac vein.

  • Superficial Veins:

    • Great Saphenous Vein:

    • Formed by the union of the dorsal digital vein of the great toe and the dorsal venous arch.

    • Ascends anterior to the medial malleolus and posterior to the medial condyle of the femur.

    • Freely anastomoses with the small saphenous vein.

    • Proximally, it traverses the saphenous opening in fascia to enter the femoral vein.

    • Small Saphenous Vein:

    • Formed by the union of the dorsal digital vein of the 5th digit and the distal venous arch.

    • Runs posterior to the lateral malleolus and lateral to the calcaneal tendon, subsequently penetrating deep fascia in the popliteal fossa.

    • Ascends between the heads of the gastrocnemius muscle to join the popliteal vein.

Perforating Veins

  • Function: Penetrate the deep fascia and serve as tributaries to the saphenous veins.

  • Location of Valves: Positioned just distal to the point where they penetrate the deep fascia.

  • Mechanism:

    • These veins cross the deep fascia obliquely, ensuring that muscle contraction causes the valves to close prior to venous compression, thereby forcing the blood proximally through a mechanism known as the musculo-venous pump.

Deep Vein Structure

  • Arrangement: Generally paired and run alongside named arteries within a vascular sheath which aids in venous return.

  • Specific Connections:

    • Popliteal vein joins with the femoral vein in the popliteal fossa.

    • The femoral vein is joined by the deep vein of the thigh.

    • Transitions into the external iliac vein as it passes deep to the inguinal ligament.