Comprehensive Review of Lower Limb and Gluteal Region Anatomy

Session Overview and Administrative Information

• Lecturer: E K LABRAM
• Faculty: FHMS (Faculty of Health and Medical Sciences)
• Date: 29/03/2023
• Primary Subject: Review of Lower Limb and Gluteal Region
• Scope of Study: Surface anatomy, osteology, muscle groups and compartments, movements, nerve supply, dermatomes, vascular supply, and lymphatic drainage.

Surface Anatomy of the Gluteal and Hip Regions

• Iliac Crest: The superior border of the wing of the ilium and the superolateral margin of the bony pelvis.
• Gluteus Maximus: The large muscle forming the rounded contour of the "cheeks" or buttocks.
• Natal/Gluteal Cleft: Commonly referred to as the "crack"; the deep groove located between the two buttocks.
• Gluteal Folds: The horizontal skin folds that define the lower limit of the gluteal "cheek."
• Femoral Triangle Landmarks for Palpation:   - Patella: The kneecap.   - Condyles of the Femur: The medial and lateral rounded projections at the distal end of the femur.   - Sartorius: Forms the lateral boundary of the femoral triangle.   - Adductor Longus: Forms the medial boundary of the femoral triangle.   - Inguinal Ligament: Forms the superior boundary of the femoral triangle.   - Iliopsoas and Pectineus: These muscles form the floor of the femoral triangle.

The Femoral Triangle

• Boundaries:   - Superior: Inguinal ligament.   - Lateral: Sartorius muscle.   - Medial: Adductor longus muscle.   - Floor: Iliopsoas and pectineus muscles.
• Contents (Memory Mnemonic: NAVL):   - Nerve: Femoral nerve.   - Artery: Femoral artery and its branches.   - Vein: Femoral vein and its tributaries.   - Lymphatics: Lymph nodes and the femoral canal.
• Detailed Arterial Contents:   - Profunda Femoris Artery: The deep artery of the thigh.   - Lateral and Medial Circumflex Arteries: Supply the femoral neck and head.   - Deep External Pudendal Artery.
• Detailed Venous/Lymphatic Contents:   - Femoral vein and its tributaries.   - Three or four deep inguinal lymph nodes located along the medial side of the femoral vein.
• Structural Components:   - Femoral Canal: The medial-most compartment containing lymphatic vessels and Cloquet's node.

The Popliteal Fossa

• Description: A diamond-shaped fossa located behind the knee joint.
• Boundaries:   - Superio-lateral: Biceps femoris muscle.   - Superio-medial: Semitendinosus and semimembranosus muscles.   - Inferior: The medial and lateral heads of the gastrocnemius muscle.
• Key Contents:   - Popliteal artery.   - Popliteal vein.   - Small saphenous vein.   - Tibial nerve.   - Common fibular nerve.   - Calcaneal (Achilles) tendon (descending from the region).

Osteology: Femur, Patella, Tibia, and Fibula

• The Femur (Thigh Bone):   - Anterior Structures: Head, fovea capitis (small pit in the head), neck, greater trochanter, lesser trochanter, intertrochanteric line, patellar surface.   - Posterior Structures: Intertrochanteric crest, gluteal tuberosity, linea aspera, medial and lateral supracondylar lines, adductor tubercle, intercondylar fossa, medial and lateral condyles, medial and lateral epicondyles.
• The Patella (Kneecap):   - Features an apex (distal point) and facets for the medial and lateral condyles of the femur.   - Surface for the patellar ligament.
• The Tibia and Fibula (Leg Bones):   - Tibia (Medial): Medial and lateral condyles, intercondylar eminence, tibial tuberosity (anterior attachment for patellar ligament), anterior crest (shin), medial malleolus.   - Fibula (Lateral): Head of fibula, lateral malleolus.   - Connections: Proximal tibiofibular joint, distal tibiofibular joint, and the interosseous membrane (connecting the shafts).

Osteology and Structure of the Foot

• Primary Functions: Supports body weight and acts as a lever during locomotion (walking).
• Tarsal Bones ($7$ bones):   - Talus: Formally known as the anklebone; situated between the tibia and fibula, articulating with both.   - Calcaneus: The heel bone; the largest tarsal bone that carries the talus and serves as the attachment point for the calcaneal (Achilles) tendon.   - Other Tarsals: Navicular bone, cuboid bone, and three cuneiform bones (lateral, intermediate, and medial).
• Metatarsals: Five bones (labeled I-V) homologous to the metacarpals of the hand.
• Phalanges: Toe bones, organized into proximal, middle, and distal phalanges (noting that toes are smaller and less nimble than fingers).
• Joints of the Foot: Includes the transverse tarsal joint and tarsometatarsal joints.

Joints and Articulations of the Lower Limb

• Hip Joint:   - Articulation: Head of femur + acetabulum of the hip bone.   - Classification: Synovial, multiaxial, ball and socket joint.
• Knee Joint (Femoropatellar):   - Articulation: Femur + Patella.   - Classification: Synovial, plane (gliding) or sellar (saddle).
• Knee Joint (Femorotibial):   - Articulation: Femur + Tibia.   - Classification: Synovial, modified hinge, biaxial (allows flexion/extension and small rotation when flexed). It is the largest joint in the body.
• Proximal Tibiofibular Joint:   - Classification: Synovial, plane (gliding).
• Distal Tibiofibular Joint:   - Classification: Fibrous (allows slight "give").
• Ankle Joint (Talocrural):   - Articulation: Tibia/Fibula + Talus.   - Classification: Synovial, uniaxial, hinge joint.

Lower Limb Movements

• General Rule: Bending on the posterior side is flexion, and bending on the anterior side is extension, with the notable exception of the hip joint.
• Hip Movements: Flexion, extension, abduction, adduction, lateral rotation, and medial rotation.
• Knee Movements: Flexion and extension.
• Ankle Movements: Dorsiflexion (lifting toes), plantarflexion (pointing toes), inversion (turning sole inward), and eversion (turning sole outward).
• Toe Movements: Flexion and extension.

Fascia and Muscle Compartments of the Thigh

• Deep Fascia (Fascia Lata): A strong, fibrous layer that encloses the thigh muscles like a tight stocking.
• Iliotibial Tract (IT Band): A lateral thickening of the fascia lata.
• Saphenous Hiatus: Also known as the saphenous opening; it has a falciform margin and is covered by cribriform fascia (sieve-like appearance).
• Compartmentalization:   - Anterior Compartment: Action includes flexing the thigh at the hip and extending the leg at the knee.   - Medial (Adductor) Compartment: Primary action is to adduct the thigh and assist in medial rotation.   - Posterior Compartment: Action includes extending the thigh and flexing the leg.
• Muscle Examples by Compartment:   - Anterior: Quadriceps femoris (Vastus medialis, intermedius, lateralis, and Rectus femoris), Sartorius.   - Medial: Adductor longus, Adductor brevis, Adductor magnus, Gracilis.   - Posterior: Biceps femoris (long and short heads), Semitendinosus, Semimembranosus.

The Gluteal Region and Muscles

• Topography: Extends from the level of the iliac crests to the gluteal fold; lies behind the pelvis.
• Function of Gluteals: Extend, rotate, and abduct the thigh.
• Muscles of the Region:   - Gluteus maximus.   - Gluteus medius.   - Gluteus minimus.   - Piriformis.   - Obturator internus.   - Superior and Inferior gemellus.   - Quadratus femoris.
• Anatomical Foramina:   - Greater Sciatic Foramen: Formed by the sacrotuberous and sacrospinous ligaments; serving as a gateway for structures entering/exiting the pelvis.   - Lesser Sciatic Foramen: Below the sacrospinous ligament.
• Gluteus Maximus Specifics:   - Description: Largest and most superficial muscle.   - Nerve Supply: Inferior gluteal nerve.   - Action: Extension and lateral rotation of the hip joint.   - Functional Roles: Chief antigravity muscle (standing from sitting), maintains posture by stabilizing the pelvis/lower back, and active during extremes of movement (running, climbing stairs).
• Intramuscular Injection: Administered in the upper outer quadrant of the gluteal region to avoid damaging the sciatic nerve; needle enters the gluteus medius or gluteus maximus.

Anatomical Relationships of the Piriformis

• Significance: Piriformis serves as the "key" to the arrangement of structures in the gluteal region.
• Superior Border Structures: Superior gluteal nerve and vessels.
• Inferior Border Structures:   - Inferior gluteal nerve and vessels.   - Pudendal nerve and vessels (briefly appears in the buttock, turns around the sacrospinous ligament, and lies medial to the ischial spine).   - Sciatic nerve.   - Posterior femoral cutaneous nerve.   - Nerves to obturator internus and quadratus femoris.

Adductor (Hunter's) Canal and Femoral Canal

• Adductor Canal:   - Description: A gutter-shaped groove extending from the apex of the femoral triangle to the adductor hiatus.   - Boundaries: Lateral (Vastus medialis), Posterior (Adductor longus and magnus), Anterior (Adductor lamina and sartorius).   - Contents: Saphenous nerve, femoral artery, femoral vein, lymphatic vessels, and loose connective tissue.
• Femoral Canal:   - Description: A space on the medial side of the femoral vein, approx. $1.3\,cm$ long.   - Boundaries of the Femoral Ring (Upper Opening): Anterior (Inguinal ligament), Medial (Lacunar ligament), Posterior (Pectineal ligament), Lateral (Femoral vein).   - Contents: Loose fatty tissue and the small lymph node of Cloquet (drains the clitoris in females or glans penis in males).

Vascular Supply of the Lower Limb

• Arteries:   - Femoral Artery: A continuation of the external iliac artery.   - Profunda Femoris: Arises approx. $4\,cm$ below the inguinal ligament from the posterolateral surface of the femoral artery; supplies all thigh muscles.   - Branches of Profunda: Lateral circumflex femoral and Medial circumflex femoral.   - Superficial Branches of Femoral Artery: Superficial epigastric, superficial iliac circumflex, and external pudendal arteries.   - Distal Flow: Continues as the Popliteal artery after passing through the adductor hiatus.
• Veins:   - Superficial Veins: Great saphenous vein, superficial epigastric vein, superficial external pudendal vein, superficial lateral femoral vein, and superficial circumflex iliac vein.

Lymphatic Drainage

• Superficial Inguinal Lymph Nodes:   - Horizontal Group (Superior): Located distal to the inguinal ligament; receives lymph from the anterior abdominal wall (below umbilicus), gluteal region, perineal region, and external genitalia.   - Vertical Group (Inferior): Located along the terminal segment of the great saphenous vein; receives lymph from nearly all superficial lymphatics of the lower limb (except posterolateral calf).
• Drainage Pathway: Efferent vessels drain into the deep inguinal lymph nodes or external iliac lymph nodes.

Neurology and Dermatomes

• Major Nerves:   - Femoral Nerve: Motor to anterior thigh (quadriceps, sartorius, iliopsoas); sensory (cutaneous) to thigh, leg, and foot (via saphenous nerve).   - Obturator Nerve: Motor to adductor muscles; sensory to the skin of the medial thigh, hip, and knee joints.   - Lateral Femoral Cutaneous Nerve: Sensory only; skin of the lateral thigh.   - Genitofemoral Nerve: Motor to cremaster muscle; sensory to scrotum/labia majora and anterior thigh.
• Key Dermatomes:   - Umbilicus: $T10$   - Hip Crease: $L1$   - Great Toe: $L4$   - 5th Toe: $S1$

Clinical Correlations

• Piriformis Syndrome: The piriformis muscle irritates or compresses the sciatic nerve, causing lower back/buttock pain and referred pain along the sciatic distribution.
• Trendelenburg Sign: Caused by weakness or paralysis of the gluteus medius (or fracture of the femoral neck/hip dislocation). Results in the contralateral (opposite side) pelvis sagging during walking/standing on the affected leg.
• Femoral Hernia:   - More common in women due to a wider pelvis and femoral canal.   - Occurs when an intestinal loop forces into the femoral ring, creating a swelling in the upper thigh.   - Differentiation: Traditionally, inguinal hernias are above/medial to the pubic tubercle, while femoral hernias are below/lateral (though technically the internal ring is always lateral to the femoral canal).
• Reflexes:   - Patella Reflex: Tests spinal levels $L3$ and $L4$.   - Ankle Reflex: Tests spinal level $S1$.